Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://star.arm.ac.uk/PhD-Thesis/files/atr/thesis_final_sd.pdf Äàòà èçìåíåíèÿ: Wed Jul 28 19:27:27 2010 Äàòà èíäåêñèðîâàíèÿ: Tue Oct 2 10:47:05 2012 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: jupiter

Development of a Software Package for the Reduction and Analysis of Video Records of Meteors

A thesis submitted for the degree of Do ctor of Philosophy

by

Prakash Atreya, B.Sc.

Armagh Observatory Armagh, Northern Ireland & Faculty of Science and Agriculture Department of Pure and Applied Physics The Queen's University of Belfast Belfast, Northern Ireland

June 2009



Acknowledgements
I want to thank Ap ostolos Christou (Tolis of the PhD, for providing articulate and available seven days a week. I thank him pro ject. This thesis would not have b een ) for all the supp ort throughout the duration extensive suggestions, and for b eing readily sincerely for his commitment to me and the successful without you.

I want to thank Rob ert Cobain for collab orating with us, and letting us use his meteor data, without which this thesis would not b e p ossible. I want to thank Geoff Coxhead and Martin Murphy for setting up and maintaining the meteor station at Armagh Observatory, providing feedback ab out the station and the meteor data, and finally for helping me with any computer issues throughout the p eriod. Thank you Martin for b eing such a wonderful guy during the Aurigid trip to California. I want to thank Stefano Bagnulo and Iwan Williams for p ositive criticisms to the thesis. I would also like to thank Simon Jeffery and Gavin Ramsey for their valuable suggestions to my thesis. I want to thank Sirko Molau and Thorsten Maue for providing me source codes for the meteor software Metrec and Metcalc resp ectively. I want to thank participants of Meteor Orbit Workshop 2006 and Virtual Observatory for Meteoroids 2008 for providing p ositive discussion on meteors. I would also like to thank Jonathan McAuliffe for providing Leonids test-data, and Eduard Bettonvil and Sontaco for providing results from their software which I have used in this thesis. I want to thank Mark, Lawarnce, Shane, Bernard, Aileen and Alison for making my stay here at Armagh very comfortable. I want to thank David Asher for providing me all the professional (and p ersonal) help throughout the duration, b e it proof reading my pap ers, or painstakingly going through my thesis. You were very much like my sup ervisor, and thank you for your valuable suggestions. I want to thank Miruna, Jonathan, Eamon, Sri, Colin, eryb ody else whose all the staff and students at Armagh Observatory. Thank you Natalie, Beb e, Timur, Tony, Anthony, David P., Caroline, Toby, Tom, Geert, Naslim, Shenghua, Ding, Avnindra, Rhona (and evnames I am forgetting) for your friendship and company. I have i


ii

had great memories with you, and hop efully, these will continue to grow wherever we all are. I want to thank my house-mates John Butler, Andy Pollack and John Driscoll for making my stay in Armagh so memorable and pleasant. The ride up-the-hill after our dinner definitely gave me energy to work through the nights. I want to thank my Dad, Mum and Dai for continuous moral and emotional supp ort. Your advice and suggestion has b een very helpful for me to successfully complete my PhD. I am happy that I was able to make you proud of me and my work. Finally, I want to thank Stephany, the most imp ortant p erson in my life, who put b elief and confidence in me, and has help ed me at every obstacle along the way. Thank you for proof reading all my pap ers, and thesis, and many times, and you probably know as much ab out my work as I do. I thank you for everything.


Publications
A list of publications resulting from work presented in this thesis is given b elow.

Refereed Publications
Atreya, P., Christou, A. A., 2008. The Armagh Observatory Meteor Camera Cluster: Overview and Status, EM&P, 102, 1-4, 263-267 Atreya, P., Christou, A. A., 2009. The 2007 Aurigid meteor outburst, MNRAS, 393, 4, 1493-1497 Koschny, D., Arlt, R., Barentsen, G., Atreya, P., Flohrer J., Jop ek, T., Knofel, A., ¨ Koten, P., Luthen, H., Mc Auliffe, J., Ob erst, J., Toth, J., Vaubaillon, J., Weryk, R., ¨ ´ and Wisniewski, M., 2009, Rep ort from the ISSI team meeting "A Virtual Observatory for meteoroids", WGN: J. Inter. meteor Org., 37:1, 21-27

Non-refereed Publications
Atreya, P., Christou, A. A., 2007. Software for the photometric and astrometric analysis of video meteors. Proceedings of the International Meteor Conference, Roden, The Netherlands, 14-17 September, 2006, Eds.: Bettonvil, F., Kac, J., 18-23 Christou, A. A., Atreya, P., 2007. The Armagh Observatory meteor camera system. Proceedings of the International Meteor Conference, Roden, The Netherlands, 14-17 September, 2006, Eds.: Bettonvil, F., Kac, J., 141-145 Atreya, P., Christou, A. A., 2007. Software for the photometric and astrometric analysis of video meteors. Proceedings of the First Europlanet Workshop on Meteor Orbit Determination, Roden, The Netherlands, 11-13 September, 2006, Eds.: Mc Auliffe, J., Koschny, D., 55-62

iii


Abstract
This work represents a detailed study of the development of a software package, SPARVM, for the reduction and analysis of meteor videos. The uncertainty in determining the p osition of a meteor was computed to b e 0.2-3.0 pixels, with a median value of 0.3 pixels. Sub-pixel accuracy (0.2-0.5 pixels) was also reached for the uncertainties in the astrometric transformation. Different modules of SPARVM were compared with 3 other software packages indicating that SPARVM is as good as, if not b etter than, those packages. SPARVM successfully reduced 6567 meteors from the Armagh Observatory meteor database. This includes analysing meteors from four different cameras at two different locations. The analysis of the double station meteors has resulted in a double station database of 457 meteors containing their radiants, velocities and orbital elements. A good agreement was found b etween the orbital elements of the -Virginids and its p ossible parent candidate 1998 SH2. A detailed analysis of the 2007 Aurigids enabled us to confirm that the outbursts occurred at the predicted time due to the debris ejected from the parent comet C/1911 N1 (Kiess) in 80 BC. The b eginning and ending heights of these Aurigids resembled those of Leonid outbursts suggesting a similarity b etween outbursts from debris of long and short p eriod comets. The first high-altitude Aurigid was observed. The presence of bright and high altitude meteors suggest the p ossibility of volatile elements, such as sodium (Na), in these meteoroids.

iv


Contents
Acknowledgements Publications Abstract List of Tables List of Figures 1 Introduction 2 Meteors, Meteoroids and Comets 2.1 2.2 2.3 2.4 Meteors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Meteoroid Dynamical Evolution . . . . . . . . . . . . . . . . . . . . . . . Observational Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.1 2.4.2 2.4.3 2.4.4 2.5 Visual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Photographic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Radio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Video . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i iii iv x 1 2 7 7 10 13 18 18 18 19 19 20 22

Software Packages for Meteor Data Analysis . . . . . . . . . . . . . . . .

3 The Armagh Observatory Meteor Cameras v


C O NT E NT S

vi

3.1 3.2

Meteor Camera Cluster . . . . . . . . . . . . . . . . . . . . . . . . . . . Meteor and Weather Records . . . . . . . . . . . . . . . . . . . . . . . .

22 25 29 29 31 32 35 43 48 48 51 52 53 54 57 57 67 70 71 74 77 77 78 80 89 93

4 SPARVM - Meteor Detection 4.1 4.2 4.3 4.4 4.5 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Video to FITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Extraction of Numb ers . . . . . . . . . . . . . . . . . . . . . . . . . . . . Meteor Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5 SPARVM - Astrometry and Photometry 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 Coordinate Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Horizontal CS - Equatorial CS . . . . . . . . . . . . . . . . . . . . . . . Formats of Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Corrections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Extracting stellar sources . . . . . . . . . . . . . . . . . . . . . . . . . . Star Catalogues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Determination of astrometric transformation parameters . . . . . . . . . Photometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sp ectral sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.10 Atmospheric Extinction . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.11 Gamma and AGC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Double Station Reduction and Orbital Element Computation 6.1 6.2 6.3 6.4 6.5 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conversion into the Equatorial CS . . . . . . . . . . . . . . . . . . . . . Double Station Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison with UFO-Orbit and KNVWS software packages .....

Computation of the Orbital Elements . . . . . . . . . . . . . . . . . . .


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vii

7 The Armagh Observatory Meteor Database 7.1 Astrometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.1 7.1.2 7.1.3 7.1.4 7.2 7.3 7.4 7.5 7.6 Cam-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

97 98 98

Cam-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 Cam-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 Cam-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Photometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 Meteor Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 Double Station Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 Geminids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 Finding parent ob jects . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 137

8 The 2007 Aurigid outburst 8.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 8.1.1 8.1.2 8.1.3 Past Aurigid Outbursts . . . . . . . . . . . . . . . . . . . . . . . 138 Prediction for the 2007 Outburst . . . . . . . . . . . . . . . . . . 138 Scientific significance . . . . . . . . . . . . . . . . . . . . . . . . . 140

8.2 8.3 8.4

Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 Data Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 8.4.1 8.4.2 8.4.3 8.4.4 8.4.5 Outburst Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 Radiant and Velocity . . . . . . . . . . . . . . . . . . . . . . . . . 150 Heights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 Orbital Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 Photometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

8.5 8.6

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158


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viii

9 Conclusions and Future Work 9.1 9.2

160

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 167

Bibliography

Appendices
A Watec CCD and Computar Optics Sp ecifications B AOMD Database

173
174 177


List of Tables
2.1 3.1 3.2 4.1 4.2 5.1 Working list of visual meteor showers from IMO . . . . . . . . . . . . . Sp ecifications of cameras used in Irish double station network. ..... 10 22 23 34 43

Location of the meteor stations. . . . . . . . . . . . . . . . . . . . . . . . Sum of the pixel difference b etween numb ers with reference set of digits Numb er of frames p er second. . . . . . . . . . . . . . . . . . . . . . . . . The mean Az. and Alt. for 10 videos using a single set of transformation parameters. .............................

65

6.1

Comparison of double station results b etween SPARVM, KNVWS and UFO-Orbit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

6.2

(V2 ). 6.3

Difference in velocities observed from station-1 (V1 ) and station-2

.....................................

93

Comparison b etween the orbital elements of 2007/12/23 04:03:37 UT Ursid and comet 8P/Tuttle. ........................ 96

7.1 7.2 7.3 7.4 7.5 7.6

Filtering of Cam-1.1 and Cam-1.9 data according to the different criteria. 100 Filtering of Cam-2.2 and Cam-2.9 data according to the different criteria. 105 Filtering of Cam-3.3 and Cam-3.9 data according to the different criteria. 107 Filtering of Cam-4 data according to the different criteria. . . . . . . . 109 Filtering of Cam-4 data. . . . . . . . . . . . . . . . . . . . . . . . . . . 112 Meteor detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

ix


LIST OF TABLES

x

7.7 7.8 7.9

Radiant and V of Geminids.

. . . . . . . . . . . . . . . . . . . . . . . 133

Orbital elements of Geminids and 3200 Phaethon. . . . . . . . . . . . . 134 Orbital elements of established shower with unknown or unsure parent ob jects compared with those of p ossible parents. . . . . . . . . . . . . . 135

8.1 8.2 8.3 8.4 8.5 8.6 8.7

Past Aurigid Outbursts . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 Predictions made for 2007 Aurigid outburst . . . . . . . . . . . . . . . . 140 Observing station in California. . . . . . . . . . . . . . . . . . . . . . . . 142 Sp ecifications of cameras used at Fremont Peak and Lick Observatory. . 142 Radiant and Velocity of Aurigids . . . . . . . . . . . . . . . . . . . . . . 151 Heights of Aurigids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 Osculating orbital elements of Aurigids . . . . . . . . . . . . . . . . . . . 154


List of Figures
2.1 2.2 2.3 Halley's comet takes ab out 76 years to orbit the Sun. . . . . . . . . . . . Non-gravitational forces acting on a meteoroid. . . . . . . . . . . . . . . Time offset of Leonid meteoroids ahead of and b ehind parent comet 55 P/Temp el-Tuttle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 3.1 3.2 3.3 3.4 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 Shap e of Geminid meteoroid stream . . . . . . . . . . . . . . . . . . . . Camera setup at Armagh Observatory. . . . . . . . . . . . . . . . . . . . Weather records at Armagh Observatory . . . . . . . . . . . . . . . . . . 16 17 24 25 11 14

Meteors detected by Cam-1, Cam-2 and Cam-3 at Armagh Observatory 26 Total and double station meteors observed. . . . . . . . . . . . . . . . . Flowchart of the SPARVM software .................... 27 30 32 33 35 36 38 39 40 41 42

Examples of sup erimp osed numb ers. . . . . . . . . . . . . . . . . . . . . The sum of the columns for the numb ers `2',`0',`0',`5',`1' and `2'. . . . . A video frame is comp osed of an odd and an even field . . . . . . . . . . Example of a frame with a bright meteor. . . . . . . . . . . . . . . . . . The 500 brightest pixels in the example frame. . . . . . . . . . . . . . . Centroid of a meteor source. . . . . . . . . . . . . . . . . . . . . . . . . . Meteor p osition in image coordinate system . . . . . . . . . . . . . . . . Meteor p ositions after pro jected onto b est fit line. . . . . . . . . . . . .

4.10 Position residuals for an individual meteor source . . . . . . . . . . . . .

xi


LIST OF FIGURES

xii

4.11 Distance travelled by meteor b etween adjacent frames . . . . . . . . . . 4.12 Time difference b etween the adjacent frames ...............

44 46 47 49 50 54 56 59 63 64 66 67 68

4.13 Light curve of a meteor starting . . . . . . . . . . . . . . . . . . . . . . . 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 Coordinate systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Transformation b etween Cartesian and spherical coordinate systems. . . Examples of (i) A single frame (ii) An averaged frame . . . . . . . . . . Star location extracted from the averaged frame. . . . . . . . . . . . . . Arrangement of three stars for computing the CD matrix . . . . . . . . Change in Azimuth and Altitude as a function of X pixel p osition. . . . Change in Azimuth and Altitude as a function of Z pixel p osition. . . . X and Z differences in ICS .......................

Az. and Alt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.10 Standard UBVRI broad-band filter resp onse curves. . . . . . . . . . . . 5.11 Instrumental magnitude vs Johnson V magnitude for the stars extracted from the example frame. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.12 Sp ectral resp onse of a typical CCD. . . . . . . . . . . . . . . . . . . . . 5.13 Instrumental magnitude vs Johnson R magnitude for the stars extracted from the example frame. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.14 Airmass as a function of zenith angle. . . . . . . . . . . . . . . . . . . . 5.15 Comparison b etween different AGC settings . . . . . . . . . . . . . . . . 6.1 6.2 6.3 6.4 A double station meteor shown in the horizontal CS . . . . . . . . . . . A double station meteor shown in the equatorial CS . . . . . . . . . . . Light curve of the example meteor. . . . . . . . . . . . . . . . . . . . . . Illustrative Schematic diagram of a double station meteor relative to the two stations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 Geodetic and geocentric latitudes. . . . . . . . . . . . . . . . . . . . . .

69 70

71 72 76 78 79 80

81 82


LIST OF FIGURES

xiii

6.6

The meteor tra jectory in spherical coordinates (latitude, longitude and height ab ove sea-level). . . . . . . . . . . . . . . . . . . . . . . . . . . . Observed velocity of the example meteor. . . . . . . . . . . . . . . . . .

86 87

6.7 6.8

and SPARVM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9

Difference of Right Ascension of the radiants computed by KNVWS/UFO-Orbit 89

and SPARVM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.10 Difference in Vobs computed by KNVWS/UFO-Orbit and SPARVM. . 6.11 Orbital elements of a celestial b ody. . . . . . . . . . . . . . . . . . . . . 6.12 Zenithal correction for the example meteor. . . . . . . . . . . . . . . . . 7.1 7.2 7.3 7.4 7.5 Distribution of the numb er of stars detected in Cam-1.1 meteor videos. Distribution of Astrometric transformation uncertainty
astr o

Difference in Declination of the radiants computed by KNVWS/UFO-Orbit

90 91 94 95 99

for Cam-1.1. 100

The p ointing of Cam-1.1. . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Distribution of the numb er of stars detected in Cam-2.2 meteor videos. 102 Distribution of the astrometric transformation uncertainty
astr o

for

Cam-2.2 meteor records. . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7.6 7.7 7.8 7.9 The p ointing of Cam-2.2. . . . . . . . . . . . . . . . . . . . . . . . . . . 104 Distribution of the numb er of stars detected in Cam-3.3 meteor videos. 105 Distribution of Astrometric transformation uncertainty
astr o

for Cam-3.3. 106

The p ointing of Cam-3.3. . . . . . . . . . . . . . . . . . . . . . . . . . . 107

7.10 Distribution of the numb er of stars detected in Cam-4 meteor videos. . 108 7.11 Distribution of Astrometric transformation uncertainty
astr o

for Cam-4. 109

7.12 The p ointing of Cam-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 7.13 The distribution of 7.14 The distribution of
photo photo

of photometric transformation of Cam-2. . . 111 of photometric transformation of Cam-4. . . 112

7.15 Distribution of minimum (dashed line) and maximum (b old line) magnitude of meteors observed by Cam-1. . . . . . . . . . . . . . . . . . . . 113


LIST OF FIGURES

xiv

7.16 Distribution of minimum (dashed line) and maximum (b old line) magnitude of meteors observed by Cam-2. . . . . . . . . . . . . . . . . . . 114 7.17 Distribution of minimum (dashed line) and maximum (b old line) magnitude of meteors observed by Cam-4. 7.18 Distribution of
met

. . . . . . . . . . . . . . . . . . 114

for Cam-1. . . . . . . . . . . . . . . . . . . . . . . 115

7.19 Distribution of frame numb er p er meteor in Cam-1. . . . . . . . . . . . 116 7.20 V difference b etween (i) Cam-1 and Cam-4 (steps),(ii) Cam-2 and Cam-4 (b old line), and (iii) Cam-3 and Cam-4 (dashed line). . . . . . 118

7.21 Error propagation in the velocities (V1 and V2) observed from two stations. 119 7.22 Error propagation in the p osition of the radiant (R.A. and Dec.). . . . . 120 7.23 Difference of radiant, R.A. (b old line) and Dec. (dashed line), for meteors observed by Cam-1 and Cam-3. . . . . . . . . . . . . . . . . . . . . . 121

7.24 Difference in V for meteors observed by Cam-1 and Cam-3. . . . . . 122 7.25 Difference of radiant, R.A. (b old) and Dec. (dash), for meteors observed by Cam-1 and Cam-2. . . . . . . . . . . . . . . . . . . . . . . . . . . 123

7.26 Difference of V for meteors observed by Cam-1 and Cam-2. . . . . . 124 7.27 Double station meteors for the months of Jan-Mar. . . . . . . . . . . . . 125 7.28 Double station meteors for the months of Apr-Jul. . . . . . . . . . . . . 126 7.29 Double station meteors for August. . . . . . . . . . . . . . . . . . . . . . 127 7.30 Double station meteors for the month of Sep. . . . . . . . . . . . . . . . 128 7.31 Double station meteors for the month of Oct. . . . . . . . . . . . . . . . 129 7.32 Double station meteors for the month of Nov. . . . . . . . . . . . . . . . 130 7.33 Double station meteors for the month of Dec. . . . . . . . . . . . . . . . 131 7.34 V distribution for Geminids. . . . . . . . . . . . . . . . . . . . . . . . . 132 7.35 Radiant drift of Geminids. Y axis shows R.A. - 100 and Dec. denoted

by + and resp ectively. X-axis shows the normalised time. . . . . . . . 133 Position of the node of the model 1-revolution Aurigid stream particle . 139 Schematic of double station setup in California. . . . . . . . . . . . . . . 141

8.1 8.2


LIST OF FIGURES

1

8.3

Aurigid observed at (i) 11:30:01 UT from Cam-5, (ii) 11:04:36 UT from ICAMSW and (iii) 12:02:40 UT from Bernd . . . . . . . . . . . . . . . . 144 Instrumental magnitude of several stars throughout the observing duration at Fremont Peak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

8.4

8.5 8.6 8.7 8.8 8.9

Transformation b etween Instrumental and Visual magnitude . . . . . . . 146 Metrec and SPARVM comparison of p osition and magnitude . . . . . . 147 Absolute magnitude comparison b etween four cameras . . . . . . . . . . 148 Observed Aurigid counts from Lick and Fremont Peak Observatory. . . 149

Radiant of Observed -Aurigids, the predicted radiant for the outburst, and the annual -Aurigid shower. . . . . . . . . . . . . . . . . . . . . . 151

8.10 Absolute magnitude distribution of Aurigids (Red-b old line) and Sp oradics (blue-dashed line). . . . . . . . . . . . . . . . . . . . . . . . . . . 155 8.11 Absolute magnitudes of 110436 and 105550 Aurigid. . . . . . . . . . . . 156 9.1 Northern Taurids, Southern Taurids and Orionids. . . . . . . . . . . . . 165

A.1 Technical sp ecifications of Watec (902DM2s) CCD used at Armagh Observatory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 A.2 Technical sp ecifications of Computar 6 mm focal length optical system used in Cam-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

A.3 Technical sp ecifications of Computar 3.8 mm focal length optical system used in Cam-2 and Cam-3. . . . . . . . . . . . . . . . . . . . . . . . . 176


Chapter 1

Introduction
Meteors are created by the entry of the meteoroids, grains or rocks in the Solar System, into the atmosphere. Indeed, every year, 30000 tons of interplanetary dust fall in the Earth's atmosphere. Studying meteors gives us a b etter understanding of what the Earth encounters (called the near Earth environment), and sheds light on the mechanisms leading to the delivery of extraterrestrial matter on to Earth (through the dynamics). The existence of meteor records dates back more than 2500 years and has b een mentioned in documents recovered from Roman, Greek, ancient Chinese and Japanese civilisations (Biot, 1841; Olivier, 1925; McAuliffe & Christou, 2006). But it was only after the great Leonid shower in Novemb er of 1799 and 1833 that p eople b egan to accept that meteoric phenomena are due to particles with an extraterrestrial origin. On 19th Decemb er 1865 and 6th January 1866, E. W. L. Temp el and H. Tuttle resp ectively discovered a comet which was named 1866 I/Temp el-Tuttle. Shortly after, Schiaparelli (1867), Peters (1867), and Opp olzer (1867) indep endently inferred that the orbital parameters of the 1866 Leonids had a striking resemblance to that of Temp el-Tuttle. Schiaparelli (1867) also made the association b etween the Perseid meteor shower (August) and comet 1862 I I I/Swift-Tuttle, and (Weiss, 1867) later associated the Lyrids with comet 1861 I/Thatcher. These were the first associations made b etween meteor 2


3

showers and comets, suggesting that the meteoroids originated from the comets. Whipple (1983) suggested the p ossibility of a relation b etween asteroid 3200 Phaethon and the Decemb er Geminid shower. Investigations done by various groups (Williams & Wu, 1993; Babadzhanov, 1996) confirmed that the Geminids are indeed related to 3200 Phaethon. The historical developments are describ ed in detail by Kronk (1988) and Williams (1993, 1995). Unlike comets which release dust particles through a sublimation process, asteroids eject dust through collisions. The physical similarity b etween 3200 Phaethon and ob ject 2005 UD (Jewitt & Hsieh, 2006) suggests that b oth these b odies and the Geminid stream might have originated from the same progenitor. Studying meteors and meteoroids provides clues ab out their parent ob jects: comets (Trigo-Rodriguez et al., 2009) and asteroids (Poruban et al., 2004). The strength of the c meteoroids, for instance, provides information as to the structure and evolution of the parent b ody. Through meteor studies, the relation b etween the prop erties of comets and asteroids can b e further investigated. Studying meteors gives us a b etter understanding of the near Earth environment, and sheds light on the dynamical, physical and chemical prop erties of comets, asteroids and their evolution in the solar system. Recently, ob jects in the asteroid b elt such as 133P/Elst-Pizarro, P/2005 U1 (Read) and (1999 RE70 ) have b een discovered, which showed brief cometary activity (Hsieh & Jewitt, 2006), suggesting a relationship b etween asteroids and comets. A p ossibility is that some of the asteroids are "activated" to show physical activity similar to those of comets. Another p ossibility is that some of the asteroidal ob jects are dormant comets. Hsieh & Jewitt (2006) predict that there are 15 to 150 such ob jects, named Main-BeltComets (MBCs). One way to provide the evidence of the cometary characteristics of MBCs is by relating the meteor trail left b ehind to their parent MBCs. Meteor flux monitoring can predict the meteoroid hazards in space b orne platforms (Sidorov et al., 1999) and estimate the dust distribution in the near Earth region. Meteoroids are considered a threat to artificial satellites b ecause of their high kinetic energy. Even a 1 mm grain can cause the failure of a communication satellite, and the


4

countermeasures commonly used involve a whole week of shut-down, which is a huge loss for public and private companies. The prediction for unusually high showers can reduce the workload of space agencies in protecting their machines. Most of the known meteor showers have unknown parent ob jects. This makes it imp ossible to forecast the future events, since the meteor forecasting models rely on the physical and dynamical prop erties of the parent ob jects, predominantly comets. Thus knowing a parent ob ject helps in modelling future outbursts and estimating the dust distribution in the near Earth region. As of Jan 1, 2009, there are 5943 known Near-Earth-Ob jects (NEOs) with 768 of them having a size greater than 1 km in diameter1 . 1008 of them are p otentially dangerous (higher risk of colliding with Earth) with 142 of those having a size greater than 1 km in diameter. There were 4644 new NEOs discovered b etween 1st Jan. 2001 and 1st Jan. 2009, from pro jects such as NEAT2 , Spacewatch3 , LONEOS4 and Catalina5 . At this rate, there will b e significantly more NEOs discovered in the future; some of which may b e associated with a trail of dust particles causing meteor showers. Several meteor streams are already linked to NEOs (Drummond, 1982; Olsson-Steel, 1988). Based on the orbital elements of meteor streams, one can also carefully monitor those areas in space to discover new comets and asteroids. The International Astronomical Union (IAU) meteor data centre
6

contains a list of

more than 300 showers. Several of those meteor showers have unknown or unverified parent ob jects. Jenniskens (2008); Jenniskens & Vaubaillon (2008); Jenniskens (2006) have listed tables of p ossible NEOs which could b e linked to meteor streams and suggest that more precise orbits of meteoroids are needed (eg. than those derived from radar observation). They call for a significant increase in analysis of meteoroid streams by photographic, CCD video, and intensified video techniques.
1 2 3 4 5 6

ht ht ht ht ht ht

t t t t t t

p p p p p p

://neo.jpl.nasa.gov/stats/ ://neat.jpl.nasa.gov/ ://spacewatch.lpl.arizona.edu/ ://asteroid.lowell.edu/asteroid/loneos/loneos.html ://www.lpl.arizona.edu/css/ ://www.ta3.sk/IAUC22DB/MDC2007/


5

Video Observation is one of the most advanced meteor detection techniques. Currently there are more than 40 video systems op erated by amateur and professional astronomers, as well as a numb er of packages for automatic meteor detection and analysis. Apart from these (mainly round-the-clock) meteor observation systems, there are many video observations carried out during ma jor meteor showers. Monitoring the meteor activity on a round-the-clock basis to capture any unexp ected event is the only way to draw the complete picture of the Earth's environment. In addition, it enables the recovery of meteorites provided that the meteor tra jectory is accurately estimated. For example, a bright meteor (fireball) occurred on 4th Jan. 2006 in southern France but no meteorite was recovered due to lack of accurate video observations (Trigo-Rodr´guez et al., 2006). A network of video cameras enables us to i accurately compute the meteor tra jectories, and assist in recovering the meteorite from the area where it falls. With the intention of investigating meteor activity, improve understanding of p oorly studied showers, and investigate fireballs, Armagh Observatory installed a sky monitoring system in July 2005. A need has arisen for an automated and versatile software package for the analysis of these meteors. The development of the analysis software for the meteor records from the Armagh Observatory Meteor database (AOMD) has b een compiled into this Ph.D. pro ject. The primary ob jective of the pro ject deals with the development of an astrometric and photometric analysis tool sp ecifically for video meteor records, using standard astronomical data analysis subroutines and taking into account the characteristics of off-the-shelf commercially available video cameras. A direct outcome of this effort resulted in a unique understanding of, and solution to, calibration issues related to the use of video equipment in this fashion, as well as the construction of standard correction formulae for external factors that affect camera sensitivity such as moonlight, cloud cover, and so on. The software is validated by comparing the results from known meteor showers with those from meteor databases, and by comparing our results with


6

those computed from other available software packages. Meteor astronomy comprises different sub-fields such as (i) the dynamical modelling of meteoroids and the prediction of meteor showers, (ii) the use of different methods (radio, video, visual) to observe meteors, (iii) data reduction, and (iv) the use of the reduced dataset to analyse meteors and meteoroids. The sub-fields are closely linked, eg (iv) providing feedback to (i). This thesis work is focused on the third part: developing a software package to reduce meteor records from video observations. Chapter 2 provides an introduction on meteors, meteor showers and meteoroids. Chapter 3 describ es the instruments and locations, the setup of video cameras and weather records at Armagh Observatory. Chapter 4 gives the overview of the software, extraction of frames, date and time from the video records and meteor centroiding. Chapter 5 describ es the astrometry and photometry asp ect of the software where the meteor's p osition and magnitude are transformed into standard coordinate systems. Chapter 6 describ es the process of the double station reduction and computation of the orbital elements for the double station meteors. Chapter 7 discusses the use and applicability of the software. 6567 meteors from different cameras of the Irish double station network are reduced and analysed. The radiant, velocity and orbital elements are computed for the double station subset of these meteors. The limitation and usefulness of the software is discussed in detail. The chapter ends with the analysis of double station meteors to find parent ob jects of some showers. Chapter 8 discusses the 2007 Aurigid outbursts. The software is used to reduce and analyse the Aurigid meteors and compare the result with the predicted values. This shows the nature of the science that can b e achieved by using the software develop ed during this PhD pro ject. The final Chapter (9) summarises our conclusions and p ossible future work.


Chapter 2

Meteors, Meteoroids and Comets

2.1

Meteors

Meteors are streaks of light that app ear in the sky when an interplanetary dust particle ablates in the Earth's atmosphere. The dust particle is called a meteoroid while the light itself is called a meteor or what is commonly known as a shooting star or a falling star. If a meteoroid is large enough to survive ablation, then the remaining material that falls to the ground is called a meteorite. Ablation is the process where a meteoroid is heated by the atmosphere due to air friction causing mass loss due to attrition and fragmentation. When a meteor is brighter than Venus (-4.6 magnitude) it is commonly referred to as a fireball. Dust and ice particles, which cause typical meteors, range in size b etween 0.05 mm to 10 cm in diameter (Ceplecha et al., 1998). Most meteoroids are the size of a sand grain or a p ebble, and yet produce very bright meteors due to their high velocity. A 1 cm meteoroid with a velocity of 30 km s of 60 km s
-1 -1

, or a 0.5 cm meteoroid with a velocity

would result in a meteor of ab out +0 magnitude, brighter than most of
12

the stars in the sky (Ceplecha et al., 1998). A 1P/Halley meteoroid of mass 7 x 10- kg, which enters the Earth's atmosphere at ab out 66 km s
-1

, would produce a meteor

7


2.1 Meteors

8

of +15 magnitude, whereas a corresp onding meteoroid of mass of 4 x 10-2 kg would produce a meteor of ab out -7 magnitude (Hughes, 1987). Meteors emit light in sp ectral bands which dep end on the comp osition and size of the meteoroid, the sp eed of the meteoroid and the atmospheric density. When meteoroids enter the Earth's atmosphere they are b ombarded, b oth on the atomic and the molecular level, by the constituent elements of the atmosphere. This causes deceleration and heating of the meteoroids due to transfer of energy and momentum. The kinetic energy of the particle is transferred into thermal energy causing it to vap ourise, the rate of which dep ends on the particle morphology such as its sp ecific heat capacity and chemical comp osition. As a result of the heating, the meteoroids ablate in the atmosphere. Meteors app earing to emanate from a common p oint on the sky, called a radiant, are categorised as a meteor shower. Meteor showers occur when Earth encounters streams of dust particles sharing a common orbit and occur approximately during the same time every year. The meteors from the same shower seem to radiate from a single p oint due to a p ersp ective effect, comparable to an observer looking down a long road, and seeing the sides of the road coming together at some p oint in the distance. Meteor showers are named according to the location of their radiant in the sky. For example, a meteor shower that has a radiant in the constellation of Leo is called the Leonid shower, and one in the constellation Orion, is called the Orionid shower. If a meteor is not associated with any shower then it is called a sp oradic. Sp oradics have very diffuse radiants and are active throughout the year. Sometimes Earth encounters a dense clump of dust particles which causes enhanced activity of meteors for a brief p eriod of time. This is called a meteor outburst. Observations of meteor showers can give information ab out the dust in the path of the Earth's orbit. The Zenithal Hourly Rate (ZHR) is the numb er of shower meteors p er hour an observer would see in a clear sky, with limiting stellar magnitude +6.5 and the shower radiant at the zenith. The ZHR can give us information ab out the numb er


2.1 Meteors

9

density of the meteoroids at the Earth's orbit. The duration of the shower is the interval of time when the shower activity is detectable over the sp oradic background. A shower could last from a few of days (Quadrantids, Draconids etc.) to more than a month (Perseids, Taurids etc.). The maximum or p eak is when the shower activity has reached its maximum ZHR. Some showers can have multiple p eaks where enhanced activity is observed. So by establishing the maximum p eak p eriod and the total duration of the meteor shower, the structure of a meteoroid stream can b e prob ed. The absolute magnitude of a meteor is defined as the magnitude at a distance of 100 km and at the zenith. The magnitude distribution gives information on the size distribution of particles in the meteoroid stream. The p opulation index, r , is defined as the ratio of the numb er of meteors from one magnitude class to the next fainter one. It can b e estimated observationally for each shower and gives information ab out the size distribution of meteoroids in that particular shower. Typical values of r range from 2.0 (brighter meteors) to 3.5 (fainter meteors), the average shower (in terms of magnitude) having a value of r 2.5. Table 2.1 shows the IMO7 working list of showers for the year 2005 (as a general example of showers), their times of occurrence and p eak activity, velocity (V ), radiant p osition, p opulation index r and ZHR. V is defined as the initial velocity at the top of the Earth's atmosphere b efore the start of meteoroid ablation and deceleration processes. Such meteor shower calendars are compiled annually by the International Meteor Organisation (IMO) to assist meteor observers. The official source of information ab out meteor showers is the IAU Meteor Data Centre8 , which lists the the established showers, working lists of showers and new showers. 11 new showers (Kanamori et al., 2009) were added to the list of meteor showers in April, 2009.
7 8

http://www.imo.net/calendar/2005 http://www.ta3.sk/IAUC22DB/MDC2007/


2.2 Comets

10

Table 2.1: parentheses have ZHRs except for p

Working list of visual meteor showers from IMO 2005. Maximum dates in indicate reference dates for the radiant, not true maxima. Some showers that vary from year to year. The most recent reliable gure is given here, ossibly p eriodic showers that are noted as "var." = variable.

2.2

Comets

Comets are irregularly shap ed b odies comp osed of a mixture of non-volatile grains and frozen gases. Most of the comets that we observe have highly elliptical orbits that bring them very close to the Sun and then swing them deeply into space, often b eyond the


2.2 Comets

11

orbit of Pluto. The different parts of a comet include nucleus, coma, dust-tail and ion-tail.

Figure 2.1: Halley's comet takes ab out 76 years to orbit the Sun. Source: Lick Observatory Whipple (1950) prop osed a cometary model, known as the "dirty snowbal l" model, that p ostulated a solid core or nucleus at the centre of the comet. The core is comprised of ice and dust and would often b e several kilometres in size. As the nucleus approaches the Sun, the ice b egins to sublimate and releases dust grains. This lib erated dust and gas expands to form the coma of the comet, which could b e in the order of 100,000 km across (Carroll & Ostlie, 1996). Solar radiation interacts with the coma to form the dust tail, one of the distinct features of comets. The solar wind, comp osed of electrically charged particles, interacts with the ejected gases, much of which are ionised by solar radiation after leaving the comet, to form an ion tail. Figure 2.1 shows comet 1P/Halley, with its distinct coma, dust tail, and ion tail. The velocity with which the meteoroids are ejected from the comet is called the ejection velocity Vej . Whipple (1951) defines V
ej

as:


2.2 Comets

12

Vej =

(43.0Dc /(dr

9/4

2 ) - 0.559c Dc )

(2.1)

V

ej

is related to the size (d, in cm) and density (, in g cm
-3

-3

) of the meteoroid, the

size (Dc , in km) and density (c , in g cm

) of the comet nucleus, the distance from

the Sun (r, in AU) and the heat absorption efficiency (). The ratio of the light absorb ed to the total light striking a meteoroid is defined as , and the light which is not absorb ed is reflected dep ending on the colour and surface area of the meteoroid. Equation 2.1 is formed on various assumptions including (i) that the amount of energy carried off by the outflow of water vap our is prop ortional to the energy input from Sunlight, (ii) that the outflow is uniform over the nucleus, (iii) that the meteoroid grains are spherical, and (iv) that the outflowing gas has a maxwellian distribution of velocities. The equation basically describ es the push on the meteoroid due to collisions with the water vap our against the pull of gravity of the comet. Over the years, there have b een various modifications to this formula based on different assumptions (Crifo & Rodionov, 1997; Brown & Jones, 1998). The Crifo model describ es the ejection sp eed Vd as a product of the rate of coupling () b etween gas and dust and the gas ejection sp eed (Vg ). The gas ejection sp eed Vg is calculated using:

Vg =



( kB Tg /MH2 0 )

(2.2)

where = 4/3 is the ratio of the sp ecific heats of water, kB (1.3806503 x 10- kg s
-2

23

m

2

K

-1

) is the Boltzmann constant, MH

2

0

is the mass of the water molecule and

Tg is the kinetic temp erature of the outflowing water vap our. Tg is calculated using values of incident angle of the Sunlight, heliocentric distance of ejection, and alb edo of the nucleus of the comet. The ejection sp eed Vd is computed using:


2.3 Meteoroid Dynamical Evolution

13

Vd = (( + 1)/( - 1))V The ejection velocity V
ej

g

(2.3)

is then shown by:

Ve2 = Vd2 - (8 /3)Gc R j

2 c

(2.4)

where the last term is the deceleration caused by the gravitational pull of the comet, where Rc is the radius of the comet nucleus. Whipple's formula suggests that a typical +3 magnitude Leonid meteoroid would b e ejected at a sp eed of V ejection sp eed V
ej ej

= 28.5 m s
-1

-1

whereas Crifo's formula suggest that the

12.8 m s

if only 24 % of the nucleus is active (Jenniskens,

2006). According to observations of comet Halley by the Giotto spacecraft, only 20% of the total surface area was active and resp onsible for producing all of the observed cometary activity. So this modification that only part of the surface of the comet ejects meteoroids is one of the main advantages of Crifo's model.

2.3

Meteoroid Dynamical Evolution

The comet is closest to the Sun, and exp eriences maximum heat and radiation, during p erihelion. So the ma jority of the meteoroids are ejected during p erihelion passage, rather than in the outer solar system where most of the sublimation ceases due to the low temp eratures. Since the ejection velocity is negligible compared to a comet's orbital velocity near p erihelion, the ejected meteoroids move along a similar orbit to that of the parent comet. The evolution of the meteoroid has b een widely studied (eg. Williams et al. (1979); Williams (1996); Asher (1999)). Once the meteoroids are ejected, gravitational and non-gravitational forces act up on them. The gravitational force FG b etween two b odies of mass M1 and M2 at a distance of


2.3 Meteoroid Dynamical Evolution r apart where G is the gravitational constant (6.672 x 10-
11

14 m3 kg-1 s
-2

) is shown by:

FG = G

M1 .M2 r2

(2.5)

The gravitational force of the Sun (M1 ) is the ma jor force acting on these meteoroids. But they are also affected by the gravity of other planets, moons and other large solar system b odies if these are physically close to the meteoroids.

Figure 2.2: Non-gravitational forces acting on a meteoroid. Source: Vaubaillon et al. (2005) Figure 2.2 shows the non-gravitational forces acting on a meteoroid. The solar radiation pressure is due to the momentum of solar radiation which can b e calculated by knowing the p osition, the dimension and the comp osition of the meteoroid. The effect of radiation on a meteoroid is the change in orbital energy and momentum, thus changing the temp erature and the orbital path or velocity resp ectively. The Poynting-Rob ertson effect is a solar radiation driven process, which acts op-


2.3 Meteoroid Dynamical Evolution

15

p osite to the meteoroid's velocity vector, and causes a dust grain in the solar system to slowly spiral inwards due to dissipation of orbital energy. The absorption and reemission of the radiation causes a small force against the direction of the movement of a meteoroid. In the rest frame of the Sun, the dust absorbs Sunlight in the radial direction, thus the grain's angular momentum remains unchanged. But thermal radiation is emitted more strongly in forward direction due to the Doppler effect which causes the particle to lose orbital momentum. This momentum loss p er unit time is known as the Poynting-Rob ertson force. The Yarkovsky effect is due to differences in the radiative emission at different parts of a spinning meteoroid. The part of the meteoroid facing the Sun is heated more than the side facing away. So when the meteoroid rotates, the radiative emission occurs at an angle, and has a comp onent p erp endicular to the radial direction to the Sun. This causes an anisotropic emission of the thermal photons. The effect of the Yarkovsky force is small, mostly affecting meteoroids b etween 10 cm to 10 km in diameter. The Poynting-Rob ertson effect is more prominent for smaller particles of size 1 cm. Non gravitational forces on small particles in the solar system are discussed in Burns et al. (1979). In general, the non gravitational forces exp erienced by a meteoroid mainly dep end on its size, velocity, p osition as well as comp osition. Meteoroids ejected from a comet b ecome disp ersed in time. Figure 2.3 shows the lag of Leonid meteoroids ejected from parent comet 55P/Temp el-Tuttle (Asher, 2000). Because radiation pressure causes the orbital p eriod of meteoroids to increase, the ma jority of the meteoroids are lagging b ehind the parent comet, while some meteoroids are ahead of the comet. In the figure, the numb er of revolutions since ejection is shown on the Y-axis (1 revolution for comet 55P/Temp el-Tuttle is equivalent to 33 years). It can b e observed that the meteoroid cloud is dense and compact during the 1s
t

revolution, progressively spreading out. With time, the meteoroids spread out and incur large differences in their orbital paths compared to that of their parent comet. The meteoroids from long p eriod comets spread out considerably in just 1-2 revolutions,


2.3 Meteoroid Dynamical Evolution

16

Figure 2.3: Time offset of Leonid meteoroids ahead of and b ehind parent comet 55 P/Temp el-Tuttle. Source: Asher (2000) and so it is harder to identify the parents of these disp ersed meteoroids (Steel & Elford, 1986). Even though the forces that govern the dynamical evolution of meteoroids are well understood, tracking a meteoroid over time is a complex issue. The ejection of meteoroids from the comet at each revolution changes the distribution of the dust. Figure 2.4 shows a model of the Geminid meteor stream by Ryab ova (2001). The Earth's orbit is shown by the single solid curve while the Geminid meteoroid stream, 2000 years after generation, is shown as dots from four different viewp oints. The mean orbit of 3200 Phaethon, parent of the Geminid meteoroid stream, is shown by the thick black curve. It is p ossible for some of the meteoroids to have very different orbits compared to that of their parent ob jects, and the meteoroid stream to undergo physical changes dep ending on the forces acting on them. Meteoroids orbit the Sun in elliptical orbits. Meteoroids in hyp erb olic orbits have sufficient energy to escap e and are not b ound to the Sun. Since the ma jority of comets


2.3 Meteoroid Dynamical Evolution

17

Figure 2.4: Shap e of Geminid meteoroid stream. Source: Ryab ova (2001) have elliptical orbits, and the meteoroids ejected have similar orbits to that of parent ob jects, meteoroid streams have elliptical orbits. The velocity required to escap e the Sun's gravity is given by:

ve

sc

=

2GMs r

(2.6)

where G is the gravitational constant, Ms is the mass of the Sun (1.989 x 1030 kg) and r is the distance from the Sun in Astronomical Units (1 AU = 1.496 x 1011 m). So the maximum velocity of a meteoroid in an elliptical orbit is its escap e velocity vesc , ab out 42 km s
-1

at 1 AU. The force on a b ody in a circular orbit is shown by:

Fc

ir c.

=

Mv r

2

(2.7)

Using Eqs. 2.5 and 2.7, the velocity of the Earth in a circular orbit around the Sun is ab out 30 km s
-1

given by:

vc

ir c.

=

vesc GMs = r 2

(2.8)

The maximum velocity with which a meteoroid can enter Earth's atmosphere is thus


2.4 Observational Methods
-1

18

72 km s

. On the other hand, the minimum velocity with which a meteoroid can

enter Earth's atmosphere is its escap e velocity from Earth's gravitational field, and that is 11.2 km s
-1

calculated from Eq. 2.6 where Ms is replaced by the mass of the Earth

Me (5.98 x 1024 kg) and r is replaced by the distance b etween the centre of the Earth and the top of the Earth's atmosphere. The meteor velocity dep ends on the velocity of the meteoroid and the encounter geometry, and it ranges b etween the ab ove calculated lower and upp er b ounds.

2.4
2.4.1

Observational Metho ds
Visual

The earliest method for meteor observation is the visual method. The observer scans the sky with the unaided eye, noting down meteors on gnomic or any other kind of star maps. Generally, the starting and the ending p oint of the meteor, the rate count (numb er of meteors p er hour), direction, brightness, colour, and any unusual b ehaviour are recorded. The p ositions are recorded with the aid of known stars in the vicinity of the meteors. The drawback of the visual method is the low precision of the location and magnitude of recorded meteors, and the unreliability of counts during intervals of exceptionally high rates. Due to the large uncertainty in the p osition of the meteor, reliable orbits cannot b e computed. There are many groups of amateur astronomers who contribute to meteor astronomy using this method (Jenniskens, 1994).

2.4.2

Photographic

The photographic method for rep orting meteors was develop ed during the nineteenth century. The main advantage of the photographic method is the precision in the p osition and the brightness of the meteor compared to the visual method. Most of the detailed knowledge of meteor radiation, motion, and ablation in the atmosphere originates from


2.4 Observational Methods

19

meteor photographs. A summary of developments in the photographic method can b e found in Ceplecha et al. (1998).

2.4.3

Radio

Radio and radar techniques are different from the previous two techniques in meteor stream detection. The radar method uses b oth radio wave transmitter and receiver, while the radio method uses only a receiver and a TV or radio station acting as transmitter. The meteor creates an ionisation trail while ablating in the atmosphere due to interaction with the air molecules. Radio waves are reflected by the ionisation trail and are measured by the receiver. Although the numb er of meteors can b e accurately recorded, more effort is usually needed to extract accurate information from the radio data. A summary of various groups active in radio meteor studies is given by (Baggaley, 1995; Wislez, 2007).

2.4.4

Video

Video observation is the youngest and one of the most advanced meteor detection techniques. The p ositional accuracy of data derived from a video is higher than the visual method, and a greater numb er of meteors are captured compared to the photographic method. It is p ossible to obtain meteor light curves and sp ectra in addition to time, p osition, brightness, radiant, and velocity. Video observation grew rapidly in interest among meteor groups during the early 1990s. At that time, most of the video tap e analysis had to b e done manually b ecause only XT p ersonal computers and rudimentary frame grabb er cards were available. A ma jor breakthrough occurred in the mid-1990s, when image intensifiers b ecame cheap enough to b e affordable by a larger group of amateurs (Molau & Nitschke, 1996). A good review of the development of video meteor observations is given by Molau et al.


2.5 Software Packages for Meteor Data Analysis

20

(1997); Molau & Gural (2005). Currently, there are approximately 40 video systems op erated by amateur astronomers and a numb er of automatic meteor detection and analysis packages. For more information ab out different groups and organisations working in meteor astronomy readers are advised to look at the International Meteor Organisation IMO website (www.imo.net).

2.5

Software Packages for Meteor Data Analysis

Meteor analysis software can b e group ed in two categories, (a) the detection of meteors in real time and (b) the p ost-detection analysis. There are four other software tools available, namely MetRec, Meteorscan, Astro Record and the UFO Capture tool set. They all have their advantages and disadvantages. A summary and comparison of these software packages can b e found in Molau & Gural (2005).

1. Metrec (author: Sirko Molau) is a real-time meteor detection and analysis software. It does not supp ort multi-station analysis. It is only compatible with the `Meteor' or `Meteor I I' frame grabb er, and under MSDOS and Windows 95/98 exclusively. 2. Meteorscan (author: Peter Gural) is also a real-time meteor detection and analysis software package adapted to ground and airb orne observing conditions. The real time version runs under the Mac op erating system while the offline version runs under Windows 95 or later. It does not p erform multi-station analysis. 3. The Astro Record (author: Marc deLignie) program is suitable for making p ositional measurements of celestial ob jects including meteors and obtaining p ositional information on reference stars. However it is not real time and does not supp ort multi-station analysis. It works under Windows 95 or later revisions. 4. The UFO Capture (author: SonotaCo) tool set consists of different sub-packages. UFO Capture, as the name implies, deals with detecting moving ob jects in real


2.5 Software Packages for Meteor Data Analysis

21

time. UFO Analyser classifies the detected ob jects with regards to brightness, size and duration. It also sup erimp oses a sky map manually until a b est fit is obtained, at which p oint parameters for astrometry and photometry may also b e computed. The output from UFO Analyser can b e used by another program, UFO Orbit, for multi-station analysis. This program works under Windows 2000/XP/ME. The source code of this software is not readily available, and thus modification to the software cannot b e made to suit different requirements.

Apart from these, there are few sp ecific software packages available. Meteor44 (Swift et al., 2004) is used for photometry of video meteors. Falling Star (Kozak, 2008) is used for processing TV meteor data. None of the existing packages make use of the routines and other software aids (such as IDL library, AstroLib, SPICE etc.) available to the professional astronomy community. Most of these software packages are tailored for their sp ecific data (meteors), and thus only work under certain constraints. The source code, user manual, and the references to the methods used are not available in many cases. With the growing numb er of meteor stations and large quantity of unreduced meteor videos, a software package that can analyse multiple meteors automatically and efficiently is required. It is also necessary to produce accurate results with a minimum amount of input. There is clearly a lack of software that is indep endent of cameras\optics and the op erating system. There is a need for a single software package that can analyse meteors regardless of the formats of the videos and the images, and a software package which can b e modified easily to suit sp ecific users and implement methods. This work aims to provide such package.


Chapter 3

The Armagh Observatory Meteor Cameras

3.1

Meteor Camera Cluster

Armagh Observatory installed a night sky monitoring system in July 2005 with the intention to investigate particular asp ects of meteor activity such as p oorly studied showers and fireballs (Atreya & Christou, 2008). It consists of three Watec WAT-902DM2s video cameras hereafter referred to as "Cam-1", "Cam-2" and "Cam-3". Cam-1 has medium angle optics while Cam-2 and Cam-3 have wide angle optics. Cam-1 makes up a double station in combination with a similar camera ("Cam-4") set up in Bangor, Northern Ireland, approximately 73 km ENE, by amateur astronomer Rob ert Cobain. ID Cam Cam Cam Cam - - - - 1 2 3 4 Optics f0.8, 6.0 f0.8, 3.8 f0.8, 3.8 f0.8, 6.0 m m m m m m m m FOV 52 x 90 x 90 x 52 x 35 55 55 55 Pixel 0.08 0.14 0.14 0.07 FOV x 0.07 x 0.11 x 0.11 x 0.06 Azimuth 60 150 330 250 Altitude 60 60 60 60

Table 3.1: Sp ecifications of cameras used in Irish double station network.

22


3.1 Meteor Camera Cluster

23

The description of the cameras and the optical systems are shown in Table 3.1. The technical sp ecifications of the Watec CCD and the optics are shown in App endix A. It is imp ortant to emphasise again that the CCD used here are of far inferior quality compared to the ones used within the professional astronomical community. The fieldof-view of Liverp ool RATcam Telescop e
9

is only 0.135 arcsec/pixel, compared to 300

arcsec/pixel of Cam-1. The read noise of the RATcam CCD is < 5 electrons, whereas the signal-to-noise ratio is 52 db for the Watec CCD. The exact locations of the stations are given in Table 3.2. The three cameras at Armagh Observatory (Cam-1, Cam-2 & Cam-3) are p ointed at 60 altitude, and at azimuths of 60 , 150 and 330 resp ectively, covering altogether 45% of the sky. Cam-4 is p ointed at 60 altitude and at azimuth of 250 . Even though Cam-1 and Cam-4 are optimised for observing the same volume of sky, Cam-2 and Cam-3 can also observe some double station meteors, esp ecially long duration meteors, due to sky coverage overlap b etween the three cameras. Location Armagh Bangor Latitude 6 38m 59s W 5 37m 28s W Longitude 54 21m 11s N 54 39m 08s N Altitude 65 m 30 m Camera Cam-1, Cam-2, Cam-3 Cam-4

Table 3.2: Location of the meteor stations.

The three cameras are fixed firmly on the roof of Armagh Observatory as shown in Fig. 3.1. The cameras are encased in standard security camera housings to protect them against weather and other hazards. Three separate video-to-USB interfaces and USB b oards connect the cameras to a PC running Windows XP Pro. The PC clock is synchronised hourly with the atomic time broadcast on the Internet through the "NIST time" software application. The controlling software used was UFO Capture V1.0 , upgraded to V2.0 in 15th July 2007. Cam-4 used UFO capture V2.0 since the b eginning. Each video captured, whether containing a meteor or not, is visually insp ected on a
9

www.telescop e.livjm.ac.uk


3.1 Meteor Camera Cluster

24

Figure 3.1: Camera setup at Armagh Observatory.


3.2 Meteor and Weather Records

25

Hours of Camera Operation
500 Total hours Clear hours

400

Number of Hours

300

200

100

0 Aug/05 Oct/05 Dec/05 Feb/06 Apr/06 Jun/06 Aug/06 Oct/06 Dec/06

Figure 3.2: Weather records at Armagh Observatory daily basis. The start/end time of the observation, the numb er of single/double station meteors detected and the hourly weather conditions are then recorded in a log file. Hourly weather is classified as "clear" (if 90+% of the field of view is clear), "partly cloudy" (if 10+% of the field of view is clear and at least one star is visible) and "cloudy" (if less than 10% of the field of view is clear or there are no stars visible). The p ercentage of the cloud cover p er hour is estimated by eye from all videos captured through the night. The total numb er of clear hours p er day is calculated as the sum of the numb er of clear hours and half the numb er of partly cloudy hours.

3.2

Meteor and Weather Records

Figure 3.2 shows the weather record from Jul'05 until Dec'06, with the b old (red) line showing the total numb er of hours of op eration and the dashed (blue) line showing the total numb er of hours of clear sky. The cameras op erated 131 hrs/month (4.36


3.2 Meteor and Weather Records

26

Meteor detected at Armagh Observatory
180 Cam-1 Cam-2 Cam-3

160

140

Number of Meteors

120

100

80

60

40

20

0 Aug/05 Oct/05 Dec/05 Feb/06 Apr/06 Jun/06 Aug/06 Oct/06 Dec/06

Figure 3.3: Meteors detected by Cam-1, Cam-2 and Cam-3 at Armagh Observatory hrs/day) during Jun'06 and Jul'06, due to the short duration of the summer night. The op erational hours of cameras then increased gradually, reaching a maximum of 458 hrs/month (14.7 hrs/day) during Dec'05. The total numb er of op erational hours is 5168, which is 9.44 hours/day. However, the total numb er of clear hours does not follow a similar distribution compared to that of total hours of op eration. During the summer month of Jun'06, the total numb er of clear hours is 69; ab out half of the total hours of op eration are clear. During Dec'05, where the total numb er of hours of op eration is three times compared to Jun'06, the total numb er of clear hours is 115, only twice compared to Jun'06. Novemb er has the most numb er of clear hours. Figure 3.3 shows the distribution of meteors recorded by the three cameras Cam-1 (b old black line), Cam-2 (long dashed blue line) and Cam-3 (short dashed pink line). The total numb er of meteors captured by Cam-1, Cam-2, and Cam-3 are 1210, 886,


3.2 Meteor and Weather Records

27

Meteor detected at Armagh Observatory
300 Total meteors Double station meteors 250

Number of Meteors

200

150

100

50

0 Aug/05 Oct/05 Dec/05 Feb/06 Apr/06 Jun/06 Aug/06 Oct/06 Dec/06

Figure 3.4: Total and double station meteors observed. and 837 resp ectively from 1st Jul'05 until 31st Jan'07. The meteor count recorded by Cam-1 is slightly higher compared with the other two cameras. The field of view of Cam-2 and Cam-3 is larger and covers a greater volume of sky compared to Cam-1, but still recorded fewer meteors. One interpretation of this result is that the wide angle units have a lower limiting magnitude, such that Cam-1 can detect fainter meteors compared to Cam-2 and Cam-3. As the three cameras are directed at different parts of the sky, separated by 90 from each other in azimuth, an alternative explanation is that p erhaps meteor activity is not homogeneous in all the parts of the sky, and there were more meteors in the region of sky covered by Cam-1 compared to that of the other two cameras. Figure 3.4 shows the total numb er of meteors (b old red line) and double station meteors (blue dashed line). During the p eriod Feb'06 -Jun'06 only 60 meteors/month were observed, with the exception of April'06 (due to the contribution from the Lyrids). Meteor activity was high during the winter months with the highest achieved of 249


3.2 Meteor and Weather Records

28

meteors during Nov'06. The double station meteor count shows a similar trend. The two maxima for double station meteors, 63 and 53, were observed during Nov'05 and Nov'06 resp ectively. The trend of the numb er of meteors captured increasing in winter months and decreasing rapidly during summer months is predominant. One of the reasons is that most of the ma jor showers occur b etween the p eriod Jul. and Dec. The sp oradic rates are 3 times higher during these months compared to the months b etween Jan - Jun (Schmude, 1998). The numb er of clear hours of op eration during the summer months (Feb - Jul) is ab out one third compared to the winter months (Aug - Jan). During the first 18 months, each camera was op erated for 5100 hours of observation. Out of these, 1883 hours, which is a third of the total observational p eriod, were clear. 2425 single station meteors were recorded in total, 547 of those b eing double station. 212 of the double station meteors were captured by two or more cameras from the Armagh cluster. In the year 2006, there were 1492 single station and 333 double station meteors observed. The numb er of meteors recorded by the first Irish double station network is a very p ositive result, taking into account the notorious unpredictable Irish weather.


Chapter 4

SPARVM - Meteor Detection

4.1

Intro duction

SPARVM is an acronym for Software for Photometric and Astrometric Reduction of Video Meteors. It features the reduction of double station meteors and the computation of their orbital elements. It is written in IDL (Interactive Data Language) and runs on a UNIX op erating system. The primary ob jective of the software is to reduce and analyse meteor videos from the Armagh Observatory Meteor Database (AOMD). The primary input for the software are the video files recorded by the UFO-Capture software. The frames are extracted from the video and converted into .FITS format suitable for IDL. The date and time are extracted by reading the stamp ed digits on the individual frames. The p osition and flux of a meteor are computed from each frame using standard centroiding. The stellar sources in the frames are used to calculate astrometric and photometric transformation parameters. These transformation parameters are then used to convert meteor p ositions from an image coordinate system to an equatorial coordinate system (Right Ascension (R.A.) and Declination (Dec.) pairs), and from light fluxes to visual magnitudes. If a meteor is recorded by two stations, then the meteor is used for double station reduction and computation of orbital elements.

29


4.1 Introduction

30

Figure 4.1: Flowchart of the SPARVM software The flowchart of the software is shown in Fig. 4.1 and each module will b e discussed in detail in the next chapters/sections. The software was written following two ma jor guidelines: (i) full automation and (ii) modular functionality. Full automation is necessary as the Armagh Observatory Meteor Database (AOMD) contains more than 6000 meteor videos captured b efore 31s Dec. 2007, and it is thus not p ossible to analyse each of them manually.
t


4.2 Video to FITS

31

The software is divided into seven different modules as shown in Fig. 4.1. The results from each module are saved in text files, apart from the first module where the results are saved in a FITS format. The results from these text files, instead of the video frames, are used by the successive modules, thus making the software run quicker. The results of the individual modules can also b e insp ected manually by reading the text files. The modules can b e used indep endently, and imp ort/exp ort the results obtained from/to other software packages. For example, if the meteors are analysed with a software package such as Metrec, the orbital elements of these meteors can b e computed using the double station and orbital element module of SPARVM. SPARVM contains more than 50 routines (written by the author) containing more than 3000 lines of code in total. SPARVM also uses more than 150 routines already available to the scientific community such as from ASTROLIB10 (The IDL Astronomy User's Library) and SPICE11 . SPARVM is a complex piece of software, and it is b eyond the scop e of this thesis to describ e each and every routine in detail. Only the ma jor routines, and esp ecially those written by the author, will b e discussed in detail in this thesis.

4.2

Video to FITS

UFO-Capture software stores the video for each meteor in AVI format. Mplayer12 is used to extract the frames from the videos as a PNG image file. Mplayer is a movie player for (mainly) Linux and plays formats such as MPEG/VOB, AVI, ASF/WMA/WMV supp orted by many codecs. Mplayer can extract the frames in different formats such as JPEG and GIF, but PNG was chosen b ecause it is a bitmap image format that employs lossless data compression. The PNG images are then converted into FITS format using the "convert" command from Imagemagick13 .
10 11 12 13

ht ht ht ht

t t t t

p p p p

://idlastro.gsfc.nasa.gov/ ://naif.jpl.nasa.gov/naif/index.html ://www.mplayerhq.hu/design7/news.html ://www.imagemagick.org/script/index.php


4.3 Extraction of Numb ers

32

Each meteor has its own folder where the videos and their corresp onding frames are stored. All the results p ertaining to a sp ecific video are stored in their own folder. All these commands are integrated in a Perl routine14 for automatic extraction of large numb ers of video files.

4.3

Extraction of Numb ers

UFO-Capture stamps date, time, frame numb er and other reference information at the b ottom of every frame. The date and time are taken from the computer clock which is synchronised hourly with the atomic time broadcast on the Internet through the "NIST time" software application. Extraction of the date/time is necessary for the astrometric transformation of the star and meteor p osition from image coordinate to the equatorial coordinate systems.

Figure 4.2: Examples of sup erimp osed numb ers. The first from Armagh Observatory UFO-Capture V2.0, second from Armagh Observatory UFO-Capture V1.0 and third from Bangor UFO-Capture V2.0. A few general examples for the stamps are shown in Fig. 4.2. The format, size, p osition and the content of the stamp ed numb ers can vary dep ending on the settings in UFO-Capture. The first and third stamp are an example of the stamps from UFOCapture V2.0 while the second stamp is from V1.0. This can also b e seen from the precision of the time stamp, which is only up to seconds for UFO-Capture V1.0 and up to milliseconds for UFO-Capture V2.0. The stamps are different in (i) format of the date used (2007/07/24 and 01/Sep/2007), (ii) format of the time (00:48:49.145 and
14

compiled by Subash Atreya


4.3 Extraction of Numb ers

33

04:40:33), and (iii) size of the numb ers (the third stamp is smaller than the other two).

Figure 4.3: The sum of the columns for the numb ers `2',`0',`0',`5',`1' and `2'. How can we distinguish these numb ers inscrib ed on the frames accurately? The pixel values are in units of ADU (Analog to Digital Unit), which vary from 0 to 255 (for 8 bit image) dep ending on their brightness, 0 corresp onding to "black" and 255 for "bright". The pixel values for a certain numb er or letter are similar, but differ from those in other numb ers or letters. For example, the pixel values of the numb er `0' would b e similar throughout different videos and frames (if no changes are made in the settings of UFO-Capture). The sum of the columns of pixels are plotted against the row for the numb ers `2',`0',`0',`5',`1' and `2' in Fig. 4.3, in order to compare the values of the pixel sums within the stamp ed numb ers. The aim is to identify uniquely each stamp ed numb er in terms of pixel values. There is close similarity b etween the shap e and size of the two `0's, but the `0's differ significantly from either `5', `2' or `1'.


4.3 Extraction of Numb ers

34

One can use this prop erty to differentiate b etween stamp ed digits. A template for each numb er is stored as an array and associated with the numb er it represents. For example, for the second stamp, an array of 10 x 16 pixels is stored corresp onding to the numb er `2'. Thus, a reference array is stored in a database for all the numb ers b etween 0 and 9. To identify an unknown numb er, its array is matched with the reference arrays. Numb ers Zero On e Two Three Four Five Six Seven Eight Nine Dif-0 661 17897 9038 6460 15308 9999 4522 8760 4451 5502 Dif-1 18100 708 15145 14531 9421 16192 16115 17627 16354 15459 Dif-2 9012 15098 459 8591 14081 10918 9017 11727 9032 9885 Dif-3 6336 14534 8857 707 15179 7942 4487 8889 2812 3489 Dif-4 15257 9257 14092 15170 440 11149 13164 16434 15155 12408 Dif-5 9894 16034 11035 7841 11057 480 6087 10943 7980 6755 Dif-6 4440 16084 8945 4493 13221 6180 667 12469 2548 5321 Dif-7 8900 17930 11997 9009 16427 10962 12721 705 10772 8233 Dif-8 4404 16392 8981 2647 15281 8074 2451 10721 568 3553 Dif-9 5431 15507 9898 3438 12530 6755 5362 8070 3537 586

Table 4.1: Sum of the pixel difference b etween numb ers (Column 1) with reference set of digits (Column 2-11)

Table 4.1 shows an example of this method where a new set of numb ers (0-9) are matched with the stored numb ers (0-9). The difference b etween the numb ers shown in the first column (new set) and the reference arrays are shown in the columns 2-11. In the first row for `zero', the minimum difference is 661 with that of `Dif-0'. Similarly, the last row for `nine' shows the minimum difference with that of 'Dif-9'. In this way, any new numb ers can b e identified by using the minimum difference with resp ect to the stored set of arrays as a discriminator. This method is very robust b ecause the second lowest difference is almost an order of magnitude greater than the minimum difference. A similar method is used to differentiate dates in letter formats; such as 'Jan', 'Feb' where each month is taken as a unit rather than using its individual letters. A sample array for each month is stored (12 in total) and matched accordingly. This method of identifying numb ers is integrated in a routine called `numb er.pro' which can read all image files from a sp ecified folder (normally generated from one


4.4 Meteor Detection

35

video file) and generate the results in a simple `.TXT' file. It was successfully tested (manually) for 10 video files, which generated ab out 800 image files with a total of 25600 numb ers.

4.4

Meteor Detection

The building blocks of a video are the frames which are still images. In a 1 second video (for PAL system) there are 25 frames and the time difference b etween consecutive frames is 0.04 seconds. The traditional way of capturing an image is line by line, from top to b ottom, in what is known as a progressive scan. To reduce the bandwidth, it is common to capture videos in the interlaced format where only every second line is read. Figure 4.4 shows how an individual "frame" is created in the interlaced format (used by UFO-Capture) by combining two "fields". First the odd field is scanned, followed by the even field. These two fields are then combined to form a single frame. The time difference b etween consecutive fields is 0.02 seconds.

Figure 4.4: A video frame is comp osed of an odd and an even field. Source: Graft If an ob ject moves very fast, it will lead to a small difference in its p osition b etween the odd field and the even field. This produces a "combing" effect which is a series of horizontal lines that look like the teeth of a hair comb. A similar effect is produced by fast moving meteors where the centre is diffuse and the meteor is elongated with lines at the edges. The brighter meteors have associated tails which also alters the shap e of the meteor source. Unlike stellar sources whose shap e is easy to define, meteors have a wide range of shap es.


4.4 Meteor Detection

36

The centre of a star can b e calculated with sub-pixel accuracy using methods such as centroiding or Gaussian fitting. A sp ecific radius or other sp ecific parameter (dimension of a b ox, FWHM, etc.) is used to compute the centroid of a stellar source. But since meteors vary in shap e and size, a modified version of these techniques is necessary to determine the centre of the meteors.

Starlink GAIA::Skycat

00000051.fits

atr

Feb 16, 2009 at 23:29:54

Figure 4.5: Example of a frame with a bright meteor. Figure 4.5 shows an example of a frame captured by UFO-Capture. The meteor is visible in the centre of the frame. In the b ottom of the frame, date and time are shown as `2005 08 15' and `04 06 04' resp ectively. The numb er `0029' denotes this was the 29th detection of the night, and `00051' denotes the frame numb er. Only a few stars can b e identified in this frame b ecause the signal to noise ratio is very low; the sampling time is only 0.04 seconds. Identifying the stellar sources will b e discussed in the next chapter. This frame (and meteor) will b e used as an example in this section to show


4.4 Meteor Detection

37

the process of computing the meteor p osition. It is imp ortant to define a coordinate system b efore progressing further. The horizontal direction of the frame is defined as the "X-axis" and the vertical direction as the "Z-axis" (not Y-axis). This coordinate system is named Image coordinate system. The origin is defined as the centre of the image. For an image of 640 x 480 pixels, the origin would b e at x = 320.0 and z = 240.0, and the x would range from - 320.0 to + 320.0. The size of the images captured at Armagh are 640 x 480 pixels, but the size of images from the Bangor station varies b etween 640 x 480, 720 x 578 and 768 x 578 pixels. The first step is to mask the stamp ed area at the b ottom of the frame. UFO-Capture stores 35 frames as a buffer (this can b e changed in UFO-Capture settings) prior to any detection. The first 10 frames of this buffer with no meteors are averaged and used as the background frame. Subtraction of the background frame from each frame removes any static background such as stellar sources, moonlight, and other "stable" artifacts that do not change their p osition/brightness significantly in a fraction of a second. The next stage is to determine the group of pixels that b elong to the meteor. This is done in two steps: the first step estimates the size and brightness of the meteor and calculates various constraints. The second step uses these constraints to accurately identify the pixels that b elong to the meteor. Figure 4.6 shows the ADU values of the 500 brightest pixels. The gradient of the curve is small after the 100th pixel. These 100 pixels are assumed to b e pixels p ossibly b elonging to the meteor for this initial step. An arbitrary numb er of 100 is chosen for all the meteors from a manual insp ection of the first run, as the typical meteors have a "size" of 20-60 pixels. These 100 brightest pixels are then group ed according to their location. The assumption made here is that if there is a flash or any transient artifacts still remaining in the frame, then its size will b e smaller than that of the meteor. This means that the meteor will have the highest numb er of bright pixels compared to the other artifacts. For this frame, 91/100 pixels b elonged to the meteor. For the second


4.4 Meteor Detection

38

Figure 4.6: The 500 brightest pixels in the example frame. run, the numb er of threshold pixels is increased to 150, if more than 90/100 pixels were identified as meteor pixels. Similar changes in the threshold are applied if the numb er of pixels identified as `meteor' is too low (less than 50/100). Once the pixels b elonging to the meteor are identified, a centroid (C en) is calculated using:

C en =

Ci Ai Ai

(4.1)

where C and A denote the value and p osition of the pixels resp ectively, and i refers to the pixels identified as a meteor. The bright pixels affect the centre p osition of the meteor more than the faint pixels. The flux is calculated using:

F lux =

Ci

(4.2)


4.4 Meteor Detection

39

which is the sum of all the values of pixels b elonging to the meteor. Figure 4.7 shows the pixels b elonging to the meteoroid and its computed centre. In this way, rather than defining a radius, the numb er of pixels are defined. This method eliminates the difficulty in determining the centroid for irregularly shap ed meteors, as no information ab out the shap e is used during the computational process. This process might leave out faint pixels that b elong to the meteor, as gaps can b e seen in Fig. 4.7. The effect of faint pixels in determining the meteor centre and flux is less significant compared to that of the bright ones.

Figure 4.7: Centroid of a meteor source. The criteria for detecting a meteor in a given frame are that (i) it has to b e the dominant source in the frame, (ii) only one meteor p er frame can b e detected and (iii) the minimum numb er of pixels b elonging to the meteor has to b e greater than 5. This ensures that image artifacts, some of which are present even after the subtraction of


4.4 Meteor Detection

40

the background, are not mistaken for meteors.

Figure 4.8: Meteor p osition in image coordinate system The p osition of the brightest and biggest ob ject in each frame is obtained, but the meteors are recorded only in a fraction of the frames. The fact that meteors travel in one direction, and that their p ositions are relatively close to each other in adjacent frames, is used to differentiate b etween meteors and non-meteors. There needs to b e a meteor in a minimum of 3 frames for this process. The p osition of a meteor is shown in Fig. 4.8 where the meteor is travelling from top to b ottom. A b est fit line (in Fig. 4.8) is used to generate the "path" of a meteor in the image coordinate system. This path is used as a constraint towards sorting out the pixels that b elong to the meteor. During the second run, only those pixels that are in the vicinity of this "path" in the image are taken as pixels b elonging to the meteor (including other criteria mentioned in the first run), thus reducing the probability of using bright pixels


4.4 Meteor Detection

41

from other sources. After this stage, the image is analysed again through the second step. The ma jor changes in the second step are the threshold numb er for the brightest pixels and the equation of motion of the meteor.

Figure 4.9: Meteor p ositions after pro jected onto b est fit line. The computed p ositions after the second step are pro jected onto the b est fit line. Figure 4.9 shows the meteor p osition pro jected onto the straight line. The pro jection reduces uncertainties in the p erp endicular direction to the motion of the meteor. However, if it is to b e assumed that the centroiding method will produce equal amounts of uncertainty in b oth the X and Z directions, then the uncertainty for the meteor p osition along the direction of the meteor is the same as that p erp endicular to it. The residuals of the p osition with the b est-fit line are plotted against the frame numb er in Fig. 4.10. The residuals are concentrated b etween + 0.3 and - 0.3 pixels. A standard deviation (STD) for the residuals (
met

) is computed using:


4.4 Meteor Detection

42

Figure 4.10: Position residuals for an individual meteor source



met

=

1 N -1

N -1 j =0

(xj - x)2 ¯

(4.3)

For this case

met

= 0.23 pixels. The value of STD of the residuals is not the same

as the uncertainty in the p osition of the meteor, but just a way to estimate it. An error of 1.0 +
met

pixels is estimated as an error for the X and Z p osition of a meteor.
met

A distribution plot for

for all the cameras will b e shown in later chapters while
met

analysing the AOMD. It can b e noted that a value of

less than 1.0 pixel is "good"

(as in the case of this meteor), whereas a value higher than 3 pixels translates to a large uncertainty in the p osition of the meteor, so that it should b e analysed again using a different method.


4.5 Time

43

4.5

Time

An imp ortant parameter, other than the p osition of the meteor, is the time for that particular p osition. There are two typ es of uncertainties in time: absolute and relative. Absolute uncertainty is affected by the computer time b eing offset with resp ect to real time, and the same meteor recorded at a different time on a different computer/station. The computer running UFO-Capture software at Armagh Observatory constantly up dates its time through the Internet. The relative uncertainty ( ie b etween meteor frames) is the uncertainty in time b etween each measured p oint. With video technology, the time difference b etween consecutive frames is 40 milliseconds. UFO-Capture V1.0 only records the time up to the precision of a second. So, it would stamp 25 frames with the same time such as `04 40 43', the next 25 frames as `04 40 44' and so on. It is p ossible to identify the frames where this change in the second value would occur. So, from the p oint when this change in seconds occur, 0.04 seconds could b e added progressively to the next 25 frames. Numb er of Frames ch 1st 2nd 3rd 4th 12 18 19 19 4 18 18 20 1 18 19 20 11 18 19 20 7 18 18 20 ange 5th 20 16 19 10 18 in second 6th 7th 11

Files Video Video Video Video Video

1 2 3 4 5

20

11

Table 4.2: Numb er of frames p er second. This method of dividing 25 frames into equal intervals of time is a robust method. However, one assumption made is that there are exactly 25 frames in each second. Table 4.2 shows the numb er of frames in each second for five different videos. The numb er of frames are counted in b etween the change in seconds. For all counts, except the first and last, it is p ossible to find the starting p oint and the ending p oint of a second. Ignoring the first and last value for each video, there are only 18-20 frames in 1 second. The frames are dropp ed by the UFO-Capture software for the following


4.5 Time

44

reason. All 3 cameras at Armagh Observatory are run by a single computer which does not have enough CPU p ower to capture all frames, and so it drops some frames randomly. However, only one camera in Bangor is run by a computer and thus there are no frames dropp ed. Similarly, during various field trip excursion, p ortable cameras were op erated by a single computer resulting in a total of 25 frames in 1 second.

Figure 4.11: Distance travelled by meteor b etween adjacent frames If some of the frames were randomly missing, one has to determine if this is the case, and the exact p ositions in tie of these missing frames. There is no need to identify all the dropp ed frames in the entire video, but only those frames where the meteor is detected. Figure 4.9 shows the p osition of the meteor in the image coordinate system. The velocity of the meteor is relatively constant and thus the p ositions of the meteor in each frame should b e equally spaced apart. It can b e seen that there are gaps (eg. b etween the 10th and 11th p osition from b ottom right) b etween adjacent frames, and


4.5 Time

45

the distance travelled by the meteor is not consistent. This is not due to the uncertainty in determining the p osition of a meteor centre but due to dropp ed frames. Figure 4.11 shows the difference b etween the adjacent p oints with regard to the frame numb er. There are clearly two clusterings in terms of distance, one b etween 4.5 - 6.0 pixels and another b etween 10.0 - 13.0 pixels. It can b e inferred from this Figure that this meteor travels 5 pixels/frame, and where the frames have b een dropp ed the distance b etween the frame is doubled to 11 pixels. There does exist a small variability of 2 pixels due to the uncertainty in determining the exact centre of the meteor. In this way, we determine the p osition of the missing frame. For example, from Figs. 4.9 and 4.11, a frame has b een dropp ed b etween the second and third p oint (or b etween frame numb er 35 and 36). This method works accurately if there are many p oints from which to calculate statistically the most likely velocity of the meteor. But if a meteor is only detected in 3-5 frames, it is difficult to determine the distance travelled by that meteor p er frame. The problem of identifying dropp ed frames is different for videos recorded by UFOCapture V2.0. Since the time stamp of these videos records milliseconds, each frame has a unique time assigned to it. The time difference b etween adjacent frames is shown in Fig. 4.12 for a video captured by UFO-Capture V2.0. There are 4 distinct bands at 0.016 s, 0.031 s, 0.048 s and 0.062 s. This is confusing as one would exp ect only two bands, one at 0.040 s and other at 0.80 s. The reason for these 4 bands is due to the inability of UFO-Capture to prop erly stamp the time. There is a lag b etween the time when the software accesses the computer clock and stamps it in a frame. This causes the time difference to b e 0.047 s rather than exactly 0.040 s, which is a lag of 0.008 s. To comp ensate for this lag, the software then stamps other frames 0.008 s quicker, thus only 0.031 s apart. Similarly when the frames are dropp ed, the difference is 0.062 s, and to comp ensate for the lag, frames are stamp ed with a time difference of 0.031 s and 0.016 s. However, the time difference b etween the frame of 0.031 s does not follow


4.5 Time

46

Figure 4.12: Time difference b etween the adjacent frames immediately after 0.047 s; the only constraint fact is that the total time at the end has to add up. A similar plot from Cam-4 showed only two bands at 0.031 s and 0.047 s, confirming that the other two bands are due to frame droppages. The conclusion from this figure is that even though UFO-Capture stamps time up to milliseconds, its time accuracy cannot b e taken at face value. Secondly, if frames are dropp ed, the time difference b etween the adjacent frames will b e higher than 0.06 s. This way the missing frames can b e identified. The time for each frame are then recalculated using the fact that the difference b etween consecutive frame is 0.04 seconds, and taking into account the dropp ed frames. Figure 4.13 shows the flux of the meteor with the corrected time. The flux is calculated using Eq. 4.2. This module Meteor Detection computes the p osition of the meteor in image coordinates (X,Z pixel), Time (ms.) and Flux (ADU) for a meteor. The result is stored in a TXT file and can b e read by a human or any other software.


4.5 Time

47

Figure 4.13: Light curve of a meteor starting at ( 2005/08/15) 04:06:03.5 The next step in the reduction process would b e to transform their p osition into a standard sky coordinate system and convert the flux into a standard magnitude system.


Chapter 5

SPARVM - Astrometry and Photometry

5.1

Co ordinate Systems

Astrometry is the science of measuring the p osition of celestial ob jects in the sky. There are mainly four typ es of standard Coordinate Systems (CS) used to refer to the p osition of an ob ject, namely Horizontal CS, Equatorial CS, Ecliptic CS and Galactic CS. SPARVM uses horizontal (HCS) and equatorial (ECS) as the standard coordinate systems, but can optionally display the results (output) in any of the other coordinate systems. Horizontal Coordinate System: Top ocentric coordinate system in which the p osition of a b ody is describ ed by its altitude and azimuth (Seidelmann, 1992a). Altitude is the angular distance of a celestial b ody ab ove or b elow the horizon, measured along the great circles passing through the b ody and the zenith. Azimuth is the angular distance measured clockwise along the horizon from a sp ecific reference p oint (usually North) to the intersection with the great circle drawn from the zenith through the b ody on the celestial sphere. Because the earth rotates on its axis, the altitude and azimuth

48


5.1 Coordinate Systems

49

of celestial b odies are constantly changing. Equatorial Coordinate System: Celestial coordinate system in which the p osition of the b ody is describ ed by its declination and right ascension/hour angle (Seidelmann, 1992a). Declination is the angular distance on the celestial sphere north or south of the celestial equator, measured along the hour circle passing through the celestial ob ject. Right ascension is the angular distance on the celestial sphere measured westward along the celestial equator from the equinox to the hour circle passing through the celestial ob ject as shown in Fig 5.1. Hour angle is the angular distance on the celestial sphere measured westward along the celestial equator from the meridian to the hour circle that passes through a celestial ob ject.

Figure 5.1: Coordinate Systems. Source: Roy (2005) Image Coordinate System: The image coordinate system (ICS) has b een defined already in the previous chapter. The centre of the image is taken as the origin, the rows (X-pixels) and the columns (Z-pixels) are defined as the X-axis and the Z-axis resp ectively. For an image of 640 x 480 pixels, the origin would b e at (0.0, 0.0), Xrange=(-320.0, +320.0) and Z-range=(-240.0, +240.0) in pixel units. For a camera with 52 x 35 field of view capturing an image of 640 x 480 pixels, a pixel would span a field of view of 0.08 and 0.07 along the X-axis and Z-axis resp ectively.


5.1 Coordinate Systems

50

Figure 5.2: Transformation b etween Cartesian and spherical coordinate systems. HCS are illustrated by Fig. 5.2 in the Cartesian CS. On the unit sphere, any p oint P can b e describ ed by the two angles, azimuth (Az .) and altitude (Alt.). The transformation b etween the spherical (Az ., Alt.) and Cartesian (x, y , z ) coordinates are shown by:

x = cos(Alt)cos(Az ) y = cos(Alt)sin(Az ) z = sin(Alt) (5.1)

The reverse op eration of transforming Cartesian into spherical coordinates is shown by:

Alt. = arctan z / Alz . = arctan [y /x]

x2 + y

2

(5.2)


5.2 Horizontal CS - Equatorial CS

51

5.2

Horizontal CS - Equatorial CS

The transformation from the HCS to the ECS can b e divided into two main parts. The first part involves the rotation of a p osition in the HCS through an angle of [90 - latitude of the location ( )], followed by a rotation ab out the new vertical by 180 . This transforms a vector in the HCS (x , y , z ) into the ECS (x , y , z ) as shown by:

x E C S y z



x = [Rz (180)].[Ry ( )]. H C S y z

(5.3)

-1 0 0 Rz (180) = 0 -1 0 0 01 sin 0 - cos Ry ( ) = 0 1 0 cos 0 sin

(5.4)

(5.5)

The hour angle (HA) and Declination (Dec.) can b e calculated using Eq. 5.2 by replacing with HA and with Dec. Right Ascension (R.A.) can b e calculated from the HA and the Local sidereal time (LST) using the relationship:

R.A. = LS T - H A

(5.6)

This transformation is indep endent of the instrument used and dep ends on the geometry of the coordinate systems, the location (longitude) and the time. The transformation and the Eqs. 5.3 - 5.5 are describ ed by Seidelmann (1992b).


5.3 Formats of Time

52

5.3

Formats of Time

Julian date (JD) is the interval of time in days since 4713 BC January 1, Greenwich noon. For example, the Julian Day for 26th February, 2009 at noon is `2454889.0'. This numb er increases by `1' every 24 hours. It is an efficient date/time format to work with since it combines the information from different parameters of time and date such as hour, day, month and year into one single numb er. The Julian date for year (Y ), month (M ), day (D), hour (h), minutes (min) and seconds (sec) in Gregorian calendar (started after 1582 AD) is given by:

J D = 1461 · (Y + 4800 + (M - 14)/12)/4 + 367 · (M - 2 - 12 · (M - 14)/12)/12 + D - 32075 - 3 · (Y + 4900 + (M - 14)/12)/100/4 + (h + min/60 + sec/3600)/24 (5.7)

Sidereal time is the measure of time defined by the apparent diurnal motion of the equinox, a measure of rotation of the Earth with resp ect to stars rather than the Sun. One sidereal day is 23h 56min 04.090 sec. The local sidereal time can b e calculated from GST using the fact that the time decreases by 1 hour for every increase of 15 degrees longitude west of the Greenwich line (0 longitude).The formula for converting JD into Greenwich sidereal time (GST in seconds) with four constants C (Meeus, 1991) is given by:

C = [280.46061837, 360.98564736629, 0.000387933, 38710000] t = (J D - 2451545)/36525 GS T = C [0] + C [1] â t â 36525 + t2 (C [2] - t â C [3]) (5.8)


5.4 Corrections

53

5.4

Corrections

There are basically four typ es of corrections used in the transformation from the HCS to ECS. These are precession, nutation, ab erration and refraction. The direction of the rotational axis of the Earth changes due to the torque from the gravitational forces of the Sun, the Moon and the planets on the Earth's equatorial bulge. The ecliptic plane, the equatorial plane, and their intersection (equinox), which are used as reference planes and p oints resp ectively, are also in motion. This causes two typ es of motion. The smooth, long - p eriod motion of the mean p ole of the equator ab out the p ole of the ecliptic , is known as precession, and has a p eriod of ab out 26,000 years. The short-p eriod motion of the true p ole around the mean p ole with an amplitude of 9 and a p eriod up to 18.6 years is called nutation. Ab erration is the apparent angular displacement of the observed p osition of a celestial ob ject from its geometric p osition, caused by the finite velocity of light in combination with the motion of the observer and of the observed ob ject. The apparent direction of a moving celestial ob ject from a moving observer is not the same as the geometric direction of the ob ject from the observer at the same instant. Refraction is the change in direction of travel of a light ray as it passes through the atmosphere, and the amount of refraction dep ends on the altitude of the ob ject and the atmospheric conditions. Because of the b ending of light, the observed apparent altitude of the celestial ob ject is higher than its geometric true altitude. Routines from ASTROLIB (HOR2EQ.PRO and EQ2HOR.PRO) used in SPARVM to convert b etween ECS and HCS includes corrections for precession, nutation, ab erration and refraction. The corrections that are not included are the parallax effect (typically < 1 arcsec) and gravitational light deflection (typically milli-arcsec).


5.5 Extracting stellar sources

54

Figure 5.3: Examples of (i) A single frame (ii) An averaged frame

5.5

Extracting stellar sources

Transformation from the ICS to either the HCS or ECS dep ends on the camera/optics, location and time, among other factors. Transformation parameters are computed using the p ositions of the stars in the image and in the sky catalogue.


5.5 Extracting stellar sources

55

The first step is to identify the stars in a video frame. Figure 5.3 (i) shows an example of a video frame where few stars can b e identified. The signal to noise ratio (SNR) is very low, since the exp osure time is only 0.04 seconds. One way to increase the SNR is by averaging the frames, which increases the SNR by N where N is the numb er of frames. Figure 5.3 (ii) shows a average of thirty frames with a b etter SNR. More stars (including the `W' of the Cassiop eia constellation) can b e readily identified in this averaged frame whereas it remains elusive in the single frame. These frames will b e used to demonstrate the transformation from ICS to HCS. The stars are extracted from the averaged frame using routines adapted from DAOPHOT which are used by the professional astronomy community. The exact p ositions of the stars are extracted using the centroiding method. A radius is sp ecified around the approximate centre for the star. Then an inner and outer circle radius are sp ecified to compute the background. The median value of the pixels in this region is taken as the background value. The intensity of the star is computed using:
20

Is

tar

=I

star +back g r ound

-I

back g r ound

(5.9)

Centroiding is similar to finding the centre of mass of an ob ject. Typically it is accurate to a fraction (down to 0.2) of a pixel. There were 38 stars extracted from this averaged frame. The p ositions of these stars are shown in Fig. 5.4. It is p ossible that some of these star p ositions b e artifacts. The method of separating p ossible artifacts from the stars is discussed in the next section. The median of the image gives an estimate of the background signal which is 27.54 ADU. But the background might not b e the same in all the parts of the image. For example, there are some clouds in the lower right part of this averaged frame where the background value would b e higher. The mean background computed using the annulus method for 38 stars is 27.95±2.92. The small standard deviation (STD) of this
20

http://www.star.bris.ac.uk/mbt/daophot/


5.5 Extracting stellar sources

56

Figure 5.4: Star location extracted from the averaged frame. quantity and its closeness to the median value of the image indicate that the method for computing the background intensity is reliable. The instrumental magnitude I function shown by:
mag

is calculated from f lux using the logarithmic

Imag = -2.5 log10 (f lux) Th e I
mag

(5.10)

ranges from -3 (faint star) to -8 (bright star). These magnitudes need

to b e transformed into a standard magnitude system and will b e discussed in the Photometry section.


5.6 Star Catalogues

57

5.6

Star Catalogues

SPARVM uses the IDL socket command to provide a p ositional query of any catalogue in the Vizier
21

database available over the internet and return results in an IDL struc-

ture. While querying for the stars, an approximate p osition in ECS (R.A., Dec.) and the width of the search area are required. Any Catalogue that is listed in the Vizier website can b e queried, but for this particular case the Hipparcos catalogue was used. The Hipparcos catalogue is the primary product of the Europ ean Space Agency's Hipparcos Satellite. The satellite, which op erated for four years, returned high quality astrometry from Novemb er 1989 to March 1993. The readers are advised to refer to ESA (1997) for further detail of the Hipparcos catalogue. The Hipparcos catalogue contains 118,218 stars and is complete to Vmag = 7.3. The p ositional accuracies are of 1 to 3 mas in the optical at ep och 1991.25. Typical p ositional errors at a 2005 ep och are around 15 mas. Hipparcos also contains broad band visual photometric data including variability information. For the brighter stars, this is in the 1 - 2 milli magnitude range. The Hipparcos catalogue is also stored offline to retrieve information quickly for calculation. There is also an option to retrieve stars from the Hipparcos online catalogue, if a need arises. It is p ossible to retrieve additional information, such as photometric magnitudes in different bands, from other catalogues.

5.7

Determination of astrometric transformation parameters

The camera orientations in the ECS change with time. So a transformation parameter computed from a meteor video b etween these two CS only works for that particular meteor. But the cameras are fixed in the HCS, and once the camera orientations in
21

http://vizier.u-strasbg.fr/


5.7 Determination of astrometric transformation parameters

58

HCS are computed, it can b e used for other meteor videos. The extraction of the stars from the averaged frame provides p ositional information in ICS (X, Z pixel). The star catalogues provide p ositions in ECS (R.A., Dec). The star p ositions from the catalogue are converted into HCS, and referred to hereafter with catalogue values. Matching the p osition of the stars in the ICS and the HCS is a combination of a manual and an automatic process. The manual process matches through visual insp ection the p osition of some of the stars in the frame with those from the HCS by displaying the stars in XEphem22 , Starlink Gaia23 or similar software packages. At least more than 10 stars should b e matched for a robust transformation. An array of records (of X-pixel, Z-pixel, Azimuth, Altitude) for a list of stars is generated. The automatic process uses this list to calculate approximate transformation parameters. Using these parameters, all the star p osition from the ICS and the HCS are matched to calculate the final set of transformation parameters. The manual process has to b e rep eated only if the camera orientation changes significantly. For a stable station such as the one in Armagh Observatory, only one manual transformation proved adequate for the p eriod June 2005 until Decemb er 2007. SPARVM is thus ideally suited for fixed stations. The transformation from the ICS to HCS is calculated using the method describ ed by Calabretta & Greisen (2002). The ICS are first tangentially pro jected and then spherically rotated using a reference p oint. The star that is closest to the centre of the field of view is taken as a reference star. After mapping the (2D) image onto the (3D) unit sphere, the pro jected image is rotated to match the p osition of the reference star in HCS. The p osition of the reference star in the ICS is denoted by C RP I X and in HCS by C RV AL. The final information needed for transformation is the field of view of each pixels.
22 23

http://www.clearskyinstitute.com/xephem/ http://www.starlink.ac.uk/


5.7 Determination of astrometric transformation parameters

59

Once the ICS has b een pro jected and then rotated to the HCS, it is necessary to know the increment in degrees for a change in pixel in b oth X and Z direction. The three stars closest to the centre of the field of view are used to calculate the so called "C D matrix". This is a 2 by 2 array which contain information ab out the pixel field of view of the individual pixel.

Figure 5.5: Arrangement of three stars for computing the CD matrix Figure 5.5 shows three stars in the ICS and the differences b etween their p ositions
d (X1 if , Y dif 1 d , X2 if , Y dif 1 dif 2

). Similarly, the difference in the HCS b etween the star p osidif 2

d tions are (1 if ,

d , 2 if ,

).

The C D matrix is computed using the following equations:

d B = 1 if ,

dif 1

d , 2 if ,

dif 2

(5.11)


5.7 Determination of astrometric transformation parameters

60

dif Y 1 A= 0 0



d X1 if

0 0
d X1 if

d X2 if

0 0
d X2 if

Y

dif 2

(5.12)

0 0

Y

dif 1

Y

dif 2

S = A-1 B

(5.13)

S [0], S [1] CD = S [2], S [3]

(5.14)

The ICS and catalogue p ositions of 3 stars are used to solve linearly for the field of view of each pixel. An example of the C D matrix is:

0.08937, -0.00132 CD = -0.01227, 0.07679





(5.15)

The first term of the C D matrix gives the field of view in the X-direction which is 0.08937 , and the last term gives the field of view in Z direction which is 0.07679 . This is consistent with the fact that the camera used has a 52 x 35 field of view, and the images are 640 x 480 pixels wide. The C RP I X and C RV AL parameter show the p osition of the reference star in the ICS and HCS resp ectively. An example for the C RV AL and C RP I X are:

C RP I X =

-1.45,

-35.46 (5.16)

C RV AL = 61.555, 59.952


5.7 Determination of astrometric transformation parameters

61

The approximate p ointing of this camera (Cam-1) in b oth azimuth and altitude is 60 . These three parameters (C RV AL, C RP I X , C D) are sufficient to transform a p oint from the ICS to the HCS. The fields of view of the pixels are not the same throughout the entire CCD surface due to non-linearity effects at the edges of the optics. Since only three stars are used to calculate the transformation parameters, a large uncertainty in the p osition of one star would make the transformation parameter unusable. Thus this method needs to b e complemented with a statistical approach which uses the p ositional information from all the stars to reduce the uncertainties even if some of the stars are mismatched. All the catalogue star p ositions are transformed into the ICS using the ab ove transformation parameters. A 3rd order p olynomial which relates the catalogue p osition (Xcat. , Zcat. ) in ICS to its observed p osition (me
as.

) in the ICS for N stars are given by:

N



X

=
i=0 N

CX 1 + Xi + Zi + Xi Zi + Xi2 + Zi2 + Xi Zi2 + Xi2 Zi + Xi3 + Zi3 CZ 1 + Xi + Zi + Xi Zi + Xi2 + Zi2 + Xi Zi2 + Xi2 Zi + Xi3 + Zi3
i=0

meas.

- (Xi )c - (Zi )c

2 at.



Z

=

2 at.

meas.

(5.17)

The constants C

X

and C

Z

are computed such that

X

and

Z

are minimised

resp ectively. Stars with p osition residuals greater than 3 are discarded and the least square method is applied again. If any of the discarded stars b elongs to one of the three main stars used to compute C D, C RV AL and C RP I X , then the entire process is rep eated by calculating a new value for C D, C RP I X and C RV AL using only the remaining stars. This process eliminates mismatched stars b ecause of their higher residuals. For the example frame used in this section, two stars were discarded, and the p ositions of the remaining 33 stars were used to calculated the non-linearity constants C
X


5.7 Determination of astrometric transformation parameters

62

and CZ as:

CX

= (6.696, 0.946, 0.157, 1.589 â 10-5 ,

- 3.484 â 10-6 ,

- 1.196 â 10-5 , (5.18)

3.095 â 10-7 , 6.885 â 10-8 , 3.343 â 10-7 , 3.311 â 10-8 ) CZ = (0.357,

- 0.001, 1.009, 1.232 â 10-5 , 9.884 â 10-6 , 2.830 â 10-5 , - 8.5670 â 10-8 , 3.139 â 10-7 ) (5.19)

-4.573 â 10-8 , 4.312 â 10-7 ,

The standard deviation of the residual for the fit is 0.20 pixels. The 2nd and 3rd order terms are small ranging from 10-5 to 10-8 . This suggests that most of the linearity correction is contained in the 1st order terms. The first three terms for C
X

should b e 0, 1 and 0, and for CZ should b e 0, 0 and 1,

if no corrections were required. But, in this example, a large shift of +6.696 pixels and other two linear terms varying from the ideal case shows that the transformation model of C D, C RV AL and C RP I X was not ideal in the X direction. This could b e due to a large uncertainty in the X coordinates of the stars or the corresp onding coordinate in the HCS (discussed later on as well). The values of CZ are b etter with only a shift of +0.357 pixels, and the linear terms only differ in the third decimal place with the ideal case. This shows that the transformation in the Z direction was good. The least square procedure is applied not only to correct for image non-linearity, but also to correct for uncertainties produced by the C D, C RP I X and C RV AL transformations. For this reason, the `C ' constants computed from one video should not b e used with C D, C RP I X and C RV AL computed from another video, but all four parameters estimated from the same fit should always b e used together. The rate of change in altitude and azimuth as a function of X-p osition is shown in Fig. 5.6. The azimuth changes significantly while while there is very little change in the altitude. This shows that the X-axis of this particular camera is basically parallel


5.7 Determination of astrometric transformation parameters

63

Figure 5.6: Change in Azimuth and Altitude as a function of X pixel p osition. to the azimuthal direction. Similarly, Fig. 5.7 shows the resp onse of the azimuth and altitude to a change in the Z direction. Azimuth shows very little change, an indication that the Z-axis of the camera is parallel to the altitude. So, a large uncertainty over the X direction would b e more related to the uncertainty in azimuth than the altitude. If the camera was tilted significantly, then a change in the X-axis would cause a change in b oth azimuth and altitude. If the uncertainty is not the same in the X and Z direction, this will result in different uncertainties for the azimuth and the altitude. To test the accuracy and robustness of this transformation parameter, the p osition of stars from 10 different videos were transformed into the HCS and matched with their catalogue values. The mean and of the absolute differences b etween the catalogue and the computed values were computed. The date, time, numb er of stars used in the video, mean absolute difference in the azimuth with STD and mean absolute difference in the altitude with are shown in Table 8.1. The videos span a p eriod of 2 days


5.7 Determination of astrometric transformation parameters

64

Figure 5.7: Change in Azimuth and Altitude as a function of Z pixel p osition. and it can b e assumed that the camera did not move during this p eriod. The mean and are shown in arc minutes, where 1 pixel for these videos corresp onds to ab out 5 arc minutes. The transformation parameters are computed from the first video (2005/08/14 00:10:54) and used for the rest of the videos. The result shows that the typical accuracy of this set of transformation parameters is 2.2-3.6 arc minutes for the azimuth and 1.4-2.6 arcmin for the altitude. The accuracy in altitude seems b etter than that of the azimuth, which reflects the fact that the transformation parameters do a b etter job in the Z direction than in the X direction. Comparing the first 3 parameters in Eq. 5.19 again we see that CZ is much closer to the ideal values and is offset only by +0.357 pixel compared to +6.69 pixels for CX . Nonetheless, sub pixel accuracy is achieved for this transformation from the ICS to the HCS. It is imp ortant to check if the transformation is homogeneous over the entire field of


5.7 Determination of astrometric transformation parameters

65

Date YR/MN/DY 2005/08/14 2005/08/14 2005/08/14 2005/08/14 2005/08/14 2005/08/14 2005/08/15 2005/08/15 2005/08/15 2005/08/15

Time HR:MIN:SEC 00:10:54 01:19:52 01:37:29 01:38:14 01:44:05 22:41:20 01:11:44 01:29:55 01:37:32 04:06:05

Numb er of Stars 35 32 31 31 37 35 35 35 38 32

Mean Az. arc min. 2.0± 2.6 3.2± 3.5 2.2 ± 2.1 3.5± 3.1 2.2± 2.8 3.0 ± 3.5 2.8± 3.6 2.3± 2.2 2.6± 2.9 3.6± 5.3

Mean Alt. arc. min 0.4± 0.4 1.4± 1.4 1.4± 2.3 1.7± 2.8 1.2± 1.0 1.4± 2.3 1.7± 2.3 1.6± 2.6 1.2± 1.0 2.6± 2.1

Table 5.1: The mean Az. and Alt. for 10 videos using a single set of transformation parameters. view of the image. The non-linearity of the optics has b een corrected by a third order p olynomial. Figure 5.8 shows the difference in the measured and catalogue values in ICS for the particular case of the meteor (2005/08/14 01:38:14). The size of the uncertainties has b een magnified 10 times for clarity. Comparatively large differences are seen around the edges, where distance from the origin in the X direction is greater than 180 pixels. The right side of the image where three stars show large differences suggest that the transformation parameters for this region have large uncertainties. One p ossible explanation could b e that there were inadequate stars from this area in the image to compute the transformation parameter. In addition, these stars could have large uncertainties in their p osition in the ICS and the HCS. The star at (-200, -200) also has large uncertainties and lies among two other stars that show smaller p ositional uncertainty. This is probably a case of star mismatch. Figure 5.9 shows the distribution of the uncertainties in the HCS. Again, the size of the uncertainties has b een magnified 10 times for clarity. Even though the stars at the edges have more differences, there is no strict pattern visible. The star at the lower left with large uncertainty is the mismatched star. Such plots can b e used to visually identify the astrometric precision of the meteor coordinates. If the meteor is passing through the centre of the image, then sub-pixel


5.7 Determination of astrometric transformation parameters

66

Figure 5.8: X and Z differences in ICS. The errors are magnified by 10 times. precision of the astrometric transformation can b e confidently ensured, whereas if it is passing through regions with larger uncertainties, then the astrometric transformation would have a higher uncertainty compared to that at the centre of the image. The of the residuals of the p olynomial fit, Eq. 5.17, is used to assess the uncertainty in the astrometric transformation. For this example, the of the residual, called hereafter
astr o

, was merely 0.20 pixel, and resulted in sub-pixel accuracy for a further

nine videos. The cameras at Armagh Observatory are fixed, and so the astrometric parameters from one video can b e used for other videos (within a certain time p eriod) which contain either clouds or too few stars to compute the transformation parameters accurately.
astr o

and the numb er of stars used to compute the transformation param-

eters are used to assess the robustness of the fit. This will b e further describ ed in the chapter dealing with the analysis of the AOMD.


5.8 Photometry

67

Figure 5.9: Az. and Alt. differences in HCS.The errors are magnified by 10 times.

5.8

Photometry

Photometry is the measurement of the light flux (or intensity) of celestial source. The brightness of an ob ject is measured in flux (ADU) and magnitudes. There are two kinds of magnitudes: absolute and apparent. The absolute magnitude is the magnitude of an ob ject corrected to a reference distance, whereas the apparent magnitude is the brightness as seen by the observer in the absence of the atmosphere. The magnitude in this section refers to the apparent magnitude, except where otherwise sp ecified. Photometry involves computing the brightness of sources in the images, and converting them to a standard magnitude system. Computation of the flux of the stars and the meteors has already b een discussed in the previous chapter. The fluxes are converted into an instrumental magnitude (I
mag

)


5.8 Photometry

68

using:

Imag = -2.5 log10 (f lux)

(5.20)

Previously, we saw how the p ositions of the stars from the image were matched with those in the catalogue. The magnitudes of the stars in the standard system are also available through catalogues and can b e related to their magnitudes in their instrumental system.

Figure 5.10: Standard UBVRI broad-band filter resp onse curves. Source: Kitt Peak National Observatory There are various magnitudes systems dep ending on the catalogue used. SPARVM uses the Hipparcos Catalogue, and the Johnson V magnitude is taken as the standard. The UBV Johnson system is a wide band photometric system for classifying stars according to their colours. This system is defined such that the star -Lyr (Vega) has V magnitude of 0.03 and all other colours, defined as B-V and U-V, are equal to zero. The V band ranges from 400-500 nm in wavelength with the p eak resp onse at 540 nm. The resp onse curve of U, B, V, R and I bands are shown in Fig. 5.10. The bands are overlapp ed in various regions, so that for example, transmission in b oth V


5.8 Photometry ° and R band are observed at the wavelength of 600 nm (6000 A)

69

Figure 5.11: Instrumental magnitude vs Johnson V magnitude for the stars extracted from the example frame. Figure 5.11 shows the instrumental magnitude and the Johnson V magnitude of the stars from the example video used in the Astrometry section. The line fitted to the data corresp onds to

Vmag = 8.464 + 0.7275 I

mag

(5.21)

This equation can b e used to transform instrumental magnitudes into standard Johnson V magnitudes. In theory, a change in I change in V
mag mag

should translate into an equal

, since b oth magnitude systems are logarithmic, and thus the slop e of
photo

the line should b e near 1.0. The standard deviation of the residuals,

for this fit

is 0.30 magnitudes which is good considering that this is a crude calibration with no


5.9 Sp ectral sensitivity

70

other corrections made. Some of the p ossible corrections are discussed in the next sections. These corrections are not included as the default option in SPARVM.

5.9

Sp ectral sensitivity

Figure 5.12: Sp ectral resp onse of a typical CCD. Source: Romanishin The sp ectral resp onse of a CCD is different compared to that of our eyes. A typical resp onse curve for a CCD is shown in Fig. 5.12. The resp onse ranges from 400 - 700 nm (with greater than 60% relative resp onse) with a p eak at 500 nm. The exact sp ectral resp onse of the CCD used at Armagh Observatory is unknown and we have assumed it to b e similar to that of a typical CCD. The p eak resp onse of 500 nm of such a CCD would match with that of the 540 nm of Johnson V band to first order. It is p ossible to use combinations of sp ectral bands, such as V, B and R band to approximate the sp ectral resp onse of the CCD. SPARVM has an option to extract stars from other catalogues, such as I I/237 catalogue in Vizier, which contains the magnitude in U, B, V, R, I bands for the stars. Figure 5.13 shows the instrumental


5.10 Atmospheric Extinction

71

Figure 5.13: Instrumental magnitude vs Johnson R magnitude for the stars extracted from the example frame. magnitude of the stars extracted from the example frame with Johnson R magnitude. The p eak transmission resp onse of R filter is at the wavelength of 658 nm. There are fewer stars on this plot compared to Fig. 5.11 b ecause R magnitudes ware not available for all the stars. The standard deviation of the residuals in this case is 0.53 mag which is higher compared with that of the V magnitude. The smaller for the Vmag fit led us to choose this magnitude system over others.

5.10

Atmospheric Extinction

Atmospheric extinction is the reduction in brightness of stellar ob jects as their photons pass through Earth's atmosphere. The light from the stellar sources is absorb ed by water molecules and ozone and is scattered by aerosols. Light is also refracted, with


5.10 Atmospheric Extinction

72

shorter wavelengths (blue) b eing refracted more than the longer ones (red). Extinction and refraction dep end on the amount of atmosphere the light travels through b efore reaching the observer or the detector. The so called airmass dep ends on the location (height) of the observer and the zenith angle. If the airmass at the zenith is taken as unity, then the airmass at a particular zenith angle is given by:

airmass = 1/cos(zenith angle)

(5.22)

Fig. 5.14 shows the airmass as a function of zenith angle. Light from the stars travels through 40 times more airmass at the horizon compared to at the zenith. This causes the star to app ear fainter at the horizon compared to the same star at the zenith. The air-mass at 30 altitude (zenith=60 ) is 2.0, two times compared to that at the zenith.

Figure 5.14: Airmass as a function of zenith angle.


5.10 Atmospheric Extinction

73

The effect of extinction is ab out 0.28 magnitudes p er air-mass at sea level.24 . So the star would app ear to b e 0.28 magnitudes brighter at the zenith compared to an altitude of 30 . If the cameras span an altitude range of ab out 30 -90 , then the stars at lower altitude range are affected more by the extinction, compared to stars at high altitude. There are many different ways of computing atmospheric extinction. One way is to observe a set of stars throughout the night at different altitude, and compute the relationship b etween the magnitude and altitude by making an assumption that there has b een no significant atmospheric changes during the night. SPARVM features an option to select the stars from different meteor videos of a particular night, and compare their magnitudes. However, it should not b e assumed that there is little variation throughout the night, due to moonlight and other factors. Due to these reasons, this option has to b e used manually and with caution. One way to minimise the extinction effect is by using only high altitude stars during the transformation b etween the instrumental magnitude and the Johnson V. Only stars with altitude higher than 50 were used from the example video to compute the transformation shown by

Vmag = 9.327 + 0.8601 I

mag

(5.23)

This is slightly b etter compared to Eq. 5.21; the slop e of 0.8601 is closer to 1.0 (compared to previous slop e of 0.7275) , and standard deviation of the residuals is 0.26 magnitude (as to 0.30 magnitude). This method is applicable if there are large numb er of stars in the meteor videos.
24

http://www.asterism.org/tutorials/tut28-1.htm


5.11 Gamma and AGC

74

5.11

Gamma and AGC

The Gain of a CCD determines the amount of charge (photons, e - ) collected in each pixel to a digital numb er (ADU) in the output image. A gain of 100 e- /ADU means that 100 photons are required to increase a pixel value by 1 ADU. For an 8 bit image, ADU ranges from 0 to 255. The Automatic Gain Control (AGC) controls the gain for the appropriate level of output. For example, if a pixel collects 30000 e- , then a gain of 100 e- /ADU gives it a value higher than that of 255. For this reason, the gain is increased to a higher value such as 300 e- /ADU, and this particular pixel is given a value of 100. This is very imp ortant b ecause the same star can have different pixel values dep ending on the AGC setting. A Gain of unity is common in professional astronomical CCDs. Gamma ( ) on the other hand is a non-linear op eration where the output is a p ower law as shown by:

V

OU T

=V

IN

(5.24)

V

IN

and the V

OU T

are input and output pixel values. For < 1.0, the pixel value is

compressed such that even a large change in photons will effect a prop ortionally smaller change in the output pixel value. For example, if a very bright ob ject is detected with =1 and 1 e- /ADU, then pixels with 255 - 300 e- would all b eset to 255 ADU. But if is set to 0.5, then these pixels value would b e b etween 15 - 17 ADU and different from one another. So a lower is useful for detecting bright ob jects. The Watec cameras have the option to work with different AGC and Gamma ( ) settings (as shown by the camera sp ecification in the App endix). The cameras used in Armagh Observatory and Bangor use different Gamma and AGC settings, and thus there is a need to understand the effect of these settings on the meteor videos. An exp eriment was p erformed to check the asp ect of different settings of the Watec


5.11 Gamma and AGC

75

cameras. The same set of stars were observed with different AGC and settings. Let's define the maximum pixel value for the setting AGC = HIGH and = ON as VN , H AGC = HIGH and = OFF as VF , AGC = LOW and = OFF as VF , and AGC = H L LOW and = ON as VN . L The idea was to find a transformation b etween each of these different settings, so that the images taken using different settings can b e compared with each other. The combination of AGC=LOW and =OFF did not provide any valuable result as the signal level was too low. This setting was not used for any of the stations. Figure 5.15 shows the comparison b etween VN (AGC Low) and VN (AGC High). L H The apparently linear relationship b etween the logarithm of the maximum pixel values for different settings indicates that such a transformation is p ossible. The equation of the b est fit line which can b e used to convert pixel values from one setting to another is shown by:

N N log(VL ) = -3.22 + 2.20 log(VH )

(5.25)

A comparison b etween VN and VF gave similar result with a fit and an equation to H H transform b etween these two settings. This exp eriment indicated that a transformation or law relating the different settings of and AGC for the cameras is p ossible. However, the AGC setting auto adjusts itself frequently dep ending on the background signal. As shown in the Watec manual (App endix), the AGC varies b etween 8-40 db for HIGH and 8-28 db for LOW settings. This change in AGC prevents us from using a transformation computed from one video or one night for the rest of the videos. So this method can only b e applied if the meteors recorded are in the same night with no significant change in background to induce a high enough change in AGC. Unlike astrometry, only videos that contain a large numb er of stars can b e reduced


5.11 Gamma and AGC

76

N Figure 5.15: The maximum pixel value of stars with VN and VH for =ON . L

photometrically, as the photometric transformation parameters would differ from one video to the another. However, for those meteors with sufficient stars, even the crude transformation can lead to a photometric precision of 0.2-0.5 magnitudes, as was the case for the example meteor.


Chapter 6

Double Station Reduction and Orbital Element Computation

6.1

Intro duction

The primary ob jective of SPARVM is to reduce video records of double station meteors and compute their orbital elements. A double station meteor is a meteor observed simultaneously from two different locations/stations. One way to check if meteors recorded from two different stations are double station meteors is to check their time of occurrence. If the clocks at the two stations are up-to-date, then the difference b etween the occurrence time of a meteor in the two stations should only b e a few seconds at most. During a meteor outburst, it is p ossible that two different meteors occur within a very short p eriod of time from each other. To identify these meteors as double station, their angular velocity or magnitude should b e compared. A meteor observed from a single station cannot yield the 3-dimensional p osition and the radiant without using a set of assumptions. However, the double station reduction method does not require any assumptions, and can compute the 3-dimensional p osition of a meteor at a given time through triangulation.

77


6.2 Conversion into the Equatorial CS

78

The Double Station reduction and Orbital Element calculation modules are different from other modules in that they are indep endent of the instruments (camera/optics) and the video formats used. The Meteor Detection module computes the p osition of the meteors in the video frames, and the Astrometry and Photometry module computes transformation parameters to standard coordinate systems. The p osition of a meteor in a standard coordinate system, time, and location of the stations, are used as input for the double station reduction module. This information can also b e imp orted from other software packages such as Metrec or UFO-Analyser. A routine is available within SPARVM to imp ort data from Metrec.

6.2

Conversion into the Equatorial CS

Figure 6.1: A double station meteor observed from Armagh (station-1) and Bangor (station-4) shown in the horizontal CS. Figure 6.1 shows a double station meteor observed from the Armagh Observatory


6.2 Conversion into the Equatorial CS

79

Figure 6.2: Double station meteor observed from Armagh (station-1) and Bangor (station-4) shown in the equatorial CS. cameras and the Bangor camera (referred to as station-1 and station-4 resp ectively) in the HCS. This meteor was observed on 2007/12/23 at 04:03:37 UT for 0.48 seconds (13 frames) from station-1 and 0.52 seconds (14 frames) from station-4. The same meteor is shown in the ECS in Fig 6.2. This meteor will b e used as an example to show the process of double station reduction and computation of orbital elements. The cameras and their locations have b een describ ed in the chapter " The Armagh Observatory Meteor Cameras ". Figure 6.3 shows the instrumental flux of the meteor as observed from two different locations. The time, in seconds, shown in the X axis is normalised to the start of the station-1 meteor at 0.0 seconds. The time of occurrence of the station-4 meteor has b een shifted by -4.95 seconds to match the resp ective p eaks in the light curves. These p eaks should occur at the same time regardless of which station it is observed from. Using this fact, and time-shifting the meteor curves accordingly, it is p ossible to


6.3 Double Station Reduction

80

Figure 6.3: Light curve of the example meteor. The starting time is normalised to the starting time of station-1 meteor. estimate the time difference b etween the two stations. In this case, station-4 time is 4.95 seconds ahead of station-1 time.

6.3

Double Station Reduction

The double station reduction method given by Ceplecha (1987) is used as a basis for the double station algorithm in SPARVM. All the computations are p erformed in the geocentric coordinate system. Figure 6.4 is the graphical overview of the double station reduction method. A plane that contains b oth the meteor and the station is computed for each station as shown by the shaded area. The real meteor tra jectory (m) must lie in the intersection of these planes from the two different stations with unit vectors n
1


6.3 Double Station Reduction

81

and n2 . The line that intersects these two planes gives the direction to the p oint of origin of the meteor (radiant).

Figure 6.4: Illustrative diagram of double station meteor relative to the two stations. Source: Eduard Bettonvil There are different methods of calculating the intersection of the two planes. Not all the p oints in the meteor tra jectory may lie in the plane containing the station and the meteor. The method of Ceplecha (1987) uses the notion of an "average" plane with the least residuals, and intersects them. Another method is to compute individual planes from all p ossible pairs of meteor p oints in the tra jectory, and intersect these individual planes. Borovicka (1990) compared these two methods and concluded that there was no preference of one method over the other. The first step is to convert all the coordinates into a geocentric cartesian coordinate system. The time is converted into the local sidereal time () using the longitude of the station. There are two typ es of latitudes: geographic/geodetic () and geocentric ( ). The geodetic latitude () is the angle b etween the equatorial line and the normal


6.3 Double Station Reduction

82

line that passes through the station. The geocentric latitude ( ) is the angle b etween the equatorial line and the line joining the centre of the Earth and the station. The two latitudes are illustrated in Fig. 6.4, and they are different due to the fact that the shap e of the Earth is not p erfectly spherical.

Figure 6.5: Geodetic and geocentric latitudes. Source: Koschny & McAuliffe (2007) The GPS system uses the geodetic latitude system and WGS-84 model (World geodetic System, 1984). The model defines the Earth with an equatorial radius R = 6378.137 km and the flattening constant f
const EQ

= 1/298.257223563. The flattening
P OL

constant relates the Earths's radius at the p ole (R Earth's radius at the p ole (R
P OL

) to that at the equator. The

) is computed to b e 6356.752 km from:

R

P OL

=R

EQ

(1 - f

const

)

(6.1)

The geodetic latitude of the stations are converted into geocentric latitude using:

tan( ) = (1 - f

const

)2 tan()

(6.2)

For Armagh Observatory, the geodetic and geocentric latitudes are 54.3530 and


6.3 Double Station Reduction

83

54.1706 resp ectively. The radius from the centre of the Earth to any p oint on the surface is given by:

RE =

R

2 EQ

RE Q RP O L

-R

2 P OL

tan( )2 + 1

+R

2 P OL

(6.3)

The radius at Armagh Observatory was calculated to b e 6364.055 km. The location of the observing station is transformed into rectangular coordinates as shown by

XS Y
S

= (RS + hS ) cos cos S

S S

= (RS + hS ) cos sin S = (RS + hS ) sin S

(6.4)

ZS

where R

S

is the Earth's radius at the observing station, hs is the station height

ab ove sea level, is the geocentric latitude and s is the local sidereal time (LST). The s coordinates for station-1 (Armagh Observatory) are computed as XS 1 = -3073.1775, Y
S1

= 2105.7318 and Z

S1

= 5159.7972. Similarly, the location of station-4 (Bangor)

is converted to cartesian coordinates. The next step is to convert the measured p ositions of the meteor into rectangular coordinates. The Right Ascension () and Declination () are converted into , , and using:

= = =

cos cos cos sin sin (6.5)


6.3 Double Station Reduction

84

The radial term (similar to (R+h) term in Eqs. 6.4) is not known for this transformation. The essence of the double station algorithm lies in identifying this radial term, so that the 3-d p osition of the meteor can b e computed. The plane containing the station and the meteor tra jectory can now b e computed as all the coordinates are in the same system. An "average" plane solution, defined as the solution of least residuals is computed using

k

(ai + bi + ci )
i=1

2

=

min

(6.6) (6.7) (6.8)

a + b + c + d = 0

a, b and c are the three comp onents of a vector that is p erp endicular to the average plane containing b oth the meteor tra jectory and the station. The choice of these unknown vectors is estimated such that
min

is minimised where k is the numb er of

measured meteor p oints. The plane is expressed in the , , coordinates. Thus a plane can b e defined by a normal vector (a, b, c) and a p oint in the plane is shown by:

aS 1 XS 1 + bS 1 Y

S1

+ cS 1 ZS 1 = -dS

1

(6.9)

The p osition of the station is used to compute d. For example, the p osition of station-1 (XS 1 ,YS 1 , ZS 1 ), which has already b een calculated from Eq 6.4, and p erp endicular vector (aS 1 , bS 1 , cS 1 ), can b e used in Eq. 6.9 to compute dS 1 . The equation of a plane containing the Armagh Observatory and the tra jectory of the example meteor is shown by


6.3 Double Station Reduction

85

0.149

S1

- 0.982S 1 - 0.114

S1

= 3120.05

(6.10)

Similarly, the equation of a plane containing station-4 and the meteor tra jectory can b e computed. The line of intersection of these two planes gives the real tra jectory of the meteor. The line of intersection of two planes is shown by a simple vector formula

^ ^ LR = S 1 â S 4

(6.11)

^ ^ where S1 and S4 are the unit vectors of the normals of the plane : (a^ 1 , b^1 , cS 1 ) ^ S S ^^ and (a^ 4 , bS 4 , cS 4 ) resp ectively. S The vector LR gives the direction of the meteor, and by converting the three comp onents (Lx , Ly , Lz ) to spherical coordinates by using the inverse of Eq. 6.5, the R.A. and Dec. of its radiant can b e computed. The conversion actually gives the p osition of either the radiant or the anti-radiant; if the zenith angle is greater than 90 then this is the anti-radiant. For this sp ecific example, the p osition of the radiant was calculated to b e = 215.39 and = 75.60 . The reliability of the solution dep ends on the geometry of the plane. Ceplecha (1987) quantifies the statistical weight of the intersection of the two planes by Q b etween the two planes, defined as:
AB

, the angle

cosQ

AB

=| aS 1 aS 4 + bS 1 b

S4

+ cS 1 cS 4 | (a2 1 + b S

2 S1

+ c2 1 )(a2 4 + b S S

2 S4

+ c2 4 ) (6.12) S

The statistical significance is prop ortional to sin2 Q

AB

and greater for larger angles


6.3 Double Station Reduction

86

b etween the planes. The Q

AB

computed for the example meteor is 62.52 suggesting

a high statistical weight. The other parameter used to assess the goodness of the intersection of the planes is
min

, which indicates the disp ersion of the individual p oints

in the meteor tra jectory from the average plane. The maximum angular separation of the meteor p oints from the average plane, including b oth stations for the example meteor, is 2.85 arc minutes which is approximately 0.6 pixels.

Height [km]
105 100 95 90 -5.9 54.48 54.45 -5.8 54.42 -5.7

Longitude [deg]

Latitude [deg]

Figure 6.6: The meteor tra jectory in spherical coordinates (latitude, longitude and height ab ove sea-level). The final part of the computation process requires the pro jection of the tra jectory p oints onto the average plane. Then by using the inverse of Eqs. 6.5 the and coordinates for the meteor tra jectory can b e computed. Using the inverse of Eqs. 6.1- 6.4, the latitude, longitude, and height of the meteors can b e calculated. The example meteor tra jectory as seen from station-1 is shown in Fig. 6.6 in Earth-fixed spherical


6.3 Double Station Reduction

87

coordinates (Latitude, Longitude, Height (ab ove sea-level)). The parameters computed for the double station meteors are the p osition of the radiant, the angle b etween the station-to-meteor planes, the geocentric (X, Y, Z) and the spherical (latitude, longitude, height) p osition of each p oint in the meteor tra jectory. The observed velocity (Vobs ) is calculated by using the distance and time difference b etween all the available p oints along the tra jectory, rather than only using the first and last p oints, or only the consecutive p oints. Deceleration of the meteor is thus not taken into account, as its effect is smaller (during the fraction of a second) compared to the uncertainty of the velocity estimation. The meteor is assumed to have a constant velocity.

Figure 6.7: Observed velocity of the example meteor. The velocity for the example meteor observed from station-1 is shown in Fig. 6.7. The mean and median of the velocity are computed as 35.06 km s
-1

and 35.19 km s

-1


6.3 Double Station Reduction

88

resp ectively. The close agreement b etween the mean and the median value suggests that the result is robust even though the spread of the velocity seen in Fig. 6.7 is 5 km s
-1

. The mean value (Vobs = 35.06 km s

-1

) is taken as the observed velocity of the
-1

meteor. Similarly, the velocity from station-4 is computed to b e 34.43 km s average velocity from the two stations is 34.74±0.44 km s
-1

. Th e

. Thus, the double station

module of SPARVM is able to estimate the velocity of this meteor with high accuracy. Ceplecha et al. (1998) method (Eqs. 33-36 in his pap er) is used to transform the observed velocity into velocity infinity (V ). The V


quantity is defined as the velocity

of the meteor as it enters the Earth's atmosphere. The relation b etween the observed velocity V
obs

and V



is given by

V



=V

obs

- (r ) + gC os

(6.13)

where (r) is a deceleration function, g is the gravitational acceleration and is the entry angle of the meteoroid. The last term in the equation is due to the effect of Zenithal attraction (discussed more in Section 6.5). Apart from these two terminologies for meteor velocity, there are two more velocity terms when referring to meteors. The geocentric velocity (Vg ) of a meteor is defined as observed by a massless observer at 1 AU travelling at the same velocity as that of the Earth. This is, in fact, the velocity of the meteor at infinity with resp ect to Earth. The heliocentric velocity (Vh ) is the velocity of the meteor with resp ect to the Sun. The example meteor occurred on 2007/12/23 at 04:03:37. The p osition of the radiant computed was = 215.39 and = 75.60 with V


= 33.04 km s

-1

. The p eak of the

Ursid meteor shower usually occurs on Decemb er 22nd , with the radiant at = 217 and = 76 and V


= 33 km s

-1

(2005 IMO calendar Table 2.1 ). Consequently, the

example meteor can b e identified as a part of the Ursid meteor stream.


6.4 Comparison with UFO-Orbit and KNVWS software packages

89

6.4

Comparison with UFO-Orbit and KNVWS software packages

The 2006 Meteor Orbit Determination Workshop (Koschny & McAuliffe, 2007) brought together various groups working in the development of meteor analysis software. To compare the different methods used in those software packages, 42 double station meteors from ESA's Leonid 2001 campaign in Australia were used as test data. The meteors were recorded using Metrec. The resulting output was fed into the various software packages to assess their double station reduction algorithms.

Figure 6.8: Difference of Right Ascension of the radiants computed by KNVWS/UFO-Orbit and SPARVM. The test data was analysed by three software packages: SPARVM, UFO-Orbit


6.4 Comparison with UFO-Orbit and KNVWS software packages

90

Figure 6.9: Difference in Declination KNVWS/UFO-Orbit and SPARVM.

of

the

radiants

computed

by

V2.05 and KNVWS. UFO-Orbit is part of the UFO package group

25

develop ed by

Sonataco; and KNVWS was develop ed by Eduard Bettonvil (Bettonvil, 2006). The result describ ed b elow originated from a series of private communications and has not yet b een published. Figure 6.8 shows the difference in R.A. of the radiant computed by KNVWS/UFO-Orbit and SPARVM. The results from KNVWS and SPARVM are comparatively less different from each other than when compared against UFO-Orbit. Figure 6.9 shows the difference in Dec. of the radiants. The KNVWS software produces similar results with SPARVM, while UFO-Orbit differs significantly from b oth for several meteors. It is not immediately obvious from these figures, but if looked at closely, a meteor which
25

http : //sonotaco.com/sof t/index.html


6.4 Comparison with UFO-Orbit and KNVWS software packages has a large difference in R.A. also has a large difference in Dec.

91

All three software packages compute velocities for each station (V1 and V2 ) and the observed velocity (Vobs ) which is the average of these two velocities. The locations of b oth stations used are in Australia. The difference in Vobs is shown in Fig 6.10. Unlike the radiants, the velocities computed by UFO-Orbit are similar to those computed by SPARVM.

Figure 6.10: Difference in Vobs computed by KNVWS/UFO-Orbit and SPARVM. The results from Fig 6.8 - 6.10 are compiled in Table 6.1 which compares the absolute mean, standard deviation, and the maximum value of the differences b etween the p osition of the radiant (R.A., Dec.) and the velocities (V1 , V2 , Vobs ). The mean difference in the R.A. of the radiant is only 0.016 and 0.131 for KNVWS and UFO-Orbit resp ectively. Similarly, the mean difference in the Dec. of the radiant is 0.022 and 0.269 for KNVWS and UFO-Orbit resp ectively. The three radiant estimates agree to


6.4 Comparison with UFO-Orbit and KNVWS software packages 0.1 for most of the meteors. The mean difference in V1 b etween SPARVM and KNVWS is 6.9 km s though the mean V2 computed only differs by 0.9 km s 3.6 km s
-1 -1 -1

92

, and even

, the mean Vobs differs by
-1

. The maximum difference in Vobs is 29.9 km s

. The difference with

UFO-Orbit is less, with the mean differences of all the velocities b eing less than 2.0 km s
-1

. The reasons for these differences have not b een prop erly investigated as the

relevant algorithms used in KNVWS and UFO-Orbit are not publicly available. Mean KNVWS R.A. (deg) Dec. (deg) V1 (km s-1 ) V2 (km s-1 ) Vobs (km s-1 ) UFO-Orbit R.A. (deg) Dec. (deg) V1 (km s-1 ) V2 (km s-1 ) Vobs (km s-1 ) 0.016 0.022 6.9 0.9 3.6 S TD 0.033 0.068 12.5 2.3 6.4 Max 0.206 0.433 56.3 14.9 29.9

0.131 0.269 1.9 1.1 1.4

0.354 0.740 2.2 3.2 2.4

2.112 3.875 12.0 17.4 14.7

Table 6.1: Comparison of double station results b etween SPARVM, KNVWS and UFO-Orbit. One way to assess the reliability of the velocity estimates is by comparing the velocities observed from the two stations. A single meteor would have the same velocity regardless of which station it is observed from. The difference, therefore, b etween V1 and V2 gives an estimate of the robustness of the algorithms. The mean, STD and maximum value for the velocity difference b etween two stations (V1 - V2 ) is shown in Table 6.2. The mean and STD difference for KNVWS is much higher compared to the other two software packages. The mean difference computed by SPARVM of 4.7 km s
-1

is the lowest. This fact alone is not enough to suggest that SPARVM has a

b etter double reduction algorithm, but is enough to show that the result obtained by SPARVM is at least as good as those of the other software packages.


6.5 Computation of the Orbital Elements Software SPARVM KNVWS UFO-Orbit Mean 4.7 10.4 5.4 S TD 10.4 13.8 10.2 Max 67.3 52.8 65.7

93

Table 6.2: Difference in velocities observed from station-1 (V1 ) and station-2 (V2 ). It is imp ortant to note that the accuracy of velocities computed from the different methods is 1-3 km s 5 km s
-1 -1

, while the velocity differences b etween the two stations are

. This could b e due to the software used to find the p osition of the meteor

(Metrec) and the uncertainty in transforming it to equatorial coordinates (R.A., Dec.). However, an accuracy of 1-3 km s of 5 arc minutes.
-1

is acceptable given the fact that cameras used in

meteor astronomy are often inexp ensive, off-the-shelf models, with a pixel field-of-view

6.5

Computation of the Orbital Elements

The p osition and velocity vectors are transformed into heliocentric orbital elements. These are defined by the p erihelion distance (qo ), eccentricity (e), inclination (i), longitude of the ascending node (), argument of p erihelion ( ), and mean anomaly at ep och (Mo ). The semi-ma jor axis (a) of the ellipse can b e computed from e and qo . Some of these angles are shown in Fig. 6.11. The orbital elements of the meteors are computed using SPICE routines. " The SPICE data sets are often called "kernels" or "kernel files". SPICE kernels are comp osed of navigation and other ancillary information that has b een structured and formatted for easy access and correct use by the planetary science and engineering communities. SPICE kernels are produced by the most knowledgeable sources of such information, usually located at a mission op erations center. They should include or b e accompanied by metadata, consistent with flight pro ject data system and NAIF standards, that provide p edigree and other descriptive information needed by prosp ective


6.5 Computation of the Orbital Elements

94

Figure 6.11: Orbital elements of a celestial b ody. Source: LaSunncty. users
26

"

SPICE provides ephemerides of the Sun, the Earth and the location of any target b ody as a function of time. It also includes certain physical, dynamical and cartographic constants for target b odies, such as size and shap e sp ecifications, orientation of the spin axis and prime meridian. In addition, SPICE has robust routines to transform b etween different coordinate systems such as heliocentric CS, barycentric CS and geocentric CS. The main SPICE routine used here is OSCELT. It calculates a set of osculating conic orbital elements corresp onding to the state 6-vector (p osition, velocity) of a b ody. The gravity of the Earth acts gradually up on a meteoroid changing its direction and sp eed. The sphere of influence R calculated using
26

soi

(Opik, 1976)of the Earth on the meteoroids is

http://naif.jpl.nasa.gov/naif/spiceconcept.html


6.5 Computation of the Orbital Elements

95

R

soi

=R

SE

ME MS

(6.14)

where R

SE

is the distance b etween the Earth and the Sun, and ME and MS are the
soi

masses of the Earth and Sun resp ectively. R and 1/160th of 1 AU.

is 909476 km from the Earth's centre

Figure 6.12: Zenithal correction for the example meteor. The zenithal correction for different absolute velocities is shown in Fig. 6.12. The difference in the velocity at V


and V

soi

(velocity at a distance of R

soi

) for different

initial velocities with a fixed p osition (of the example meteor) is computed. The correction is prominent for the meteors with velocities less than 40 km s increasing rapidly b elow 20 km s
-1 -1

, with corrections

.
soi

The path of a meteoroid from R

to the Earth's atmosphere is assumed to b e a

hyp erb ola. First an assumption is made that the velocity of the meteoroid is uniform over this hyp erb ola, and using V and R
soi

, a time when the meteoroid would b e at


6.5 Computation of the Orbital Elements

96

R

soi

is roughly estimated. The meteoroid particle is then iterated forward and backward

on the hyp erb ola to calculate accurately the time and velocity when it would b e at a distance of R
soi

.

For the example Ursid meteor observed from station-1, the p osition and velocity vectors at Earth's atmosphere (P , V ) and at R
soi

(Psoi , Vsoi ) are:

P = [ - 3142.79, 2086.42, 5234.18 ] V
oi

= [ - 7.22,

- 5.06, 33.34 ] - 142621.81, 879132.98 ] (6.15)

Ps V

= [ - 184207.22, = [ - 6.54,

soi

- 5.23, 31.57 ]

The meteor has b een integrated from a distance of | P | = 6451.89 km to | Psoi | = 909476.82 km. The absolute velocity of the meteor changes from | V to | V
soi

| = 34.49 km s

-1

| = 32.67 km s

-1

. The X and the Z directions of the meteor velocity changed

more compared to the Y direction. Station Armagh Bangor 8P/Tuttle qo 0.95 0.95 1.02 a 4.86 5.40 5.69 e 0.801 0.823 0.819 i 52.90 53.31 54.98 270.81 270.81 270.34 206.06 205.83 207.50 Mo 358.24 358.55 351.45

Table 6.3: Comparison b etween the orbital elements of 2007/12/23 04:03:37 UT Ursid and comet 8P/Tuttle. The state vector at R is transformed from geocentric CS to heliocentric CS. The

soi

orbital elements for each station are computed individually. The orbital elements computed for the example Ursid meteor are shown in Table. 6.3 along with the orbital elements of parent comet 8P/Tuttle from the JPL database27 . This table is a result of all the modules (except photometry) in the SPARVM software, and it shows a good match b etween the meteor and its parent comet.

27

http://ssd.jpl.nasa.gov/


Chapter 7

The Armagh Observatory Meteor Database
The reliability of SPARVM has b een demonstrated in the last three chapters through sp ecific examples. For a b etter understanding of the usefulness and the limitations of the software, it is necessary to use the software to analyse a large numb er of meteor records, such as the ones from Armagh Observatory Meteor database (AOMD). It is also essential to differentiate b etween the limitations of the software from that of the meteors in AOMD. For example, if a meteor video contains clouds and only few stars are visible to compute the astrometric transformation parameters, then the large uncertainty in the results computed by the software is mainly due to p oor quality of meteor records. However, if there are sufficient stars in a good quality video, then the resulting uncertainty is due to software limitations. The camera sp ecifications were describ ed in Chapter 3. The cameras are named "Cam-1", "Cam-2" and Cam-3" where "Cam-1" is fitted with medium angle optics and the other two cameras with wide angle optics. The camera at Bangor is named "Cam-4". Its sp ecifications are identical to those of "Cam-1", but the settings used for AGC/Gamma are different.

97


7.1 Astrometry

98

We used meteors captured from 2005/06/08 until 2007/12/31 to test different modules of SPARVM. The meteor videos were captured using UFO-Capture V1.0 software until July 2007 by the three cameras in Armagh observatory, UFO-Capture V2.0 was used thereafter. The meteor videos observed by Cam-4 during 2007/08/21 2007/12/05 were corrupted (due to use of wrong codecs) and were not used for the test. In total, AOMD contains 6575 meteor videos until the end of 2007 distributed among the four cameras as follows: Cam-1 = 1616, Cam-2 = 1132, Cam-3 = 1153 and Cam-4 = 2674. The data from the three cameras from Armagh Observatory are further divided into two groups, with Cam-1.1, Cam-2.2 and Cam-3.3 denoting the meteor captured by UFO-Capture V1.0, and Cam-1.9, Cam-2.9 and Cam-3.9 denoting the meteors captured by UFO-Capture V2.0 by Cam-1, Cam-2 and Cam-3 resp ectively. The Cam-1.9, Cam-2.9 and Cam-3.9 sets contain 371, 224 and 278 meteor videos resp ectively.

7.1
7.1.1

Astrometry
Cam-1

Figure 7.1 shows the distribution of the numb er of stars detected in the meteor records captured by Cam-1.1. There are distinct lower and upp er cut-offs at 15 and 40 resp ectively. The upp er cut-off at 40 minimises the p ossibility that artifacts will b e considered as a star. The non-linearity correction vectors (Cx and Cz ) contain 10 scalar constants each, and thus videos with less than 15 stars detected (ie less than 30 observables) were not used for the computation of the astrometric transformation parameters. This filtering of the meteor records based on the minimum numb er of stars detected is termed "S tar - F ilter ". For Cam-1.1, S tar - F ilter = 15, since only meteor records with more than 15 stars were used in the astrometric transformation process.


7.1 Astrometry

99

Figure 7.1: Distribution of the numb er of stars detected in Cam-1.1 meteor videos. The distribution of the residuals of the p olynomial fit (
astr o

) for Cam-1.1 is shown > 1.0 not

in Fig. 7.2. The histogram bin size is 0.1 pixels, and most of the meteor records have
astr o

0.3 pixels. There were 15 videos (out of the 715 used) with
astr o

astr o

shown in this plot. Hence, only meteor videos with

0.3 pixels were used for the - F ilter

subsequent transformations. The filtering of the videos based on the maximum value of
astr o

of the meteor records is termed as

astr o

- F ilter . For Cam-1.1,

astr o

is set to 0.3 pixels. The camera p ointings calculated from the astrometric transformations for Cam-1.1 in the horizontal CS are shown in Fig. 7.3. Cam-1.1 was p ointed at azimuth = 61.98±0.21 and altitude = 62.74±0.08 . The camera seems to have shifted more in azimuth than in altitude. It is unlikely that the camera was temp orarily moved to a different p osition (such as one p oint on the top and one on the right of the figure) and then recovered its original p osition. These p ointing outliers are most likely due to large errors in the transformation parameters, ie a bad astrometry fit. So meteors that produced p ointing difference of more than ±0.4 and ±0.2 in azimuth and alti-


7.1 Astrometry

100

Figure 7.2: Cam-1.1.

Distribution of Astrometric transformation uncertainty

astr o

for

tude resp ectively from the mean p ointing were filtered out. This filtering of the meteor records based on the p ointing direction is termed the P ointing - F ilter criterion. Cam-1.9 showed similar results to those of Cam-1.1. The p ointing of Cam-1.9 was azimuth = 61.79±0.13 and altitude = 62.71±0.09 . The values of the S tar - F ilter ,
astr o

- F ilter , and P ointing - F ilter were the same as those of Cam-1.1. Meteor Videos Total S tar - F ilter astro - F ilter P ointing - F ilter Cam-1.1 1245 787 715 676 Cam-1.9 371 233 212 210

Table 7.1: Filtering of Cam-1.1 and Cam-1.9 data according to the different criteria.


7.1 Astrometry

101

Figure 7.3: The p ointing of Cam-1.1. The numb er of meteors filtered through after successive filtering for b oth Cam-1.1 and Cam-1.9 are summarised in Table 7.1. The meteor videos discarded by the S tar - F ilter criterion are 36% of the total meteor videos. This suggests that a large fraction of them contain fewer stars than the minimum necessary for a usable result. Comparatively, less than 10% of the videos are discarded by the combination of the
astr o

- F ilter and the P ointing - F ilter criteria.

SPARVM was able to accurately compute the astrometric transformation for 80% of the meteor videos containing at least 15 stars. Those meteor videos which were filtered out use the transformation parameter from the last acceptable meteor record previous to it.


7.1 Astrometry

102

7.1.2

Cam-2

Figure 7.4: Distribution of the numb er of stars detected in Cam-2.2 meteor videos. Figure 7.4 shows the distribution of the numb er of stars in meteor videos detected by Cam-2.2. Compared with Cam-1.1, we see fewer meteor videos containing more than 15 stars. Cam-2.2 is fitted with wide angle optics and its limiting magnitude is brighter compared to that of Cam-1.1. So even though it covers a larger volume of the sky, it usually detects less stars. Consequently the threshold for the S tar - F ilter is lowered to 10 stars for this camera or 20 observables. The distribution of the sharp drop after higher
astr o astr o astr o

quantity for Cam-2.2 is shown in Fig. 7.5. There is a > 1.0 not shown in this plot. One of the could b e the inclusion of meteor records

= 0.3 pixels, but unlike Cam-1.1 there are many meteors with
astr o

. There were 90 videos with

p ossible reasons for these high values of

astr o


7.1 Astrometry

103

Figure 7.5: Distribution of the astrometric transformation uncertainty Cam-2.2 meteor records. with 10-15 stars. The
astr o

astr o

for

- F ilter for Cam-2.2 is set at 0.5 pixels.

The camera p ointings calculated from the astrometric transformation for Cam-2.2 in the horizontal CS are shown in Fig. 7.6. Cam-2.2 is p ointed at azimuth = 326.0±1.8 and altitude = 65.4±1.2 . The disp ersion in the p ointing of Cam-2.2 is higher than that of Cam-1.1. As for that camera, we consider it unlikely that the p ointings far from the dense cluster are actually due to movement of the camera. They are more likely due to errors in the transformation parameters. The S tar - F ilter and
astr o

- F ilter

criterion have b een set leniently for this camera thus allowing more transformation parameter sets with large uncertainties. These meteor records are then filtered out using the P ointing - F ilter criterion. Meteors that produced p ointing differences of more than ±1.0 and ±0.5 in azimuth and altitude resp ectively from the mean p ointing


7.1 Astrometry

104

were filtered out

Figure 7.6: The p ointing of Cam-2.2. Similar results were observed for Cam-2.9. The camera p ointing was calculated to b e azimuth = 325.6±2.3 and altitude = 65.4±0.8 . The numb er of meteors filtered through after successive filterings for b oth Cam-2.2 and Cam-2.9 are summarised in Table 7.2. The numb er of meteors recorded is much smaller compared to Cam-1.1 and Cam-1.9. Even after the S tar - F ilter criterion was lowered to 10 stars, only 50% of the meteor records are retained. Astrometric transformation parameters have b een computed for only 35% of all meteor records. Yet SPARVM computed accurately the transformation for 68% of the meteor records which contained more than 10 stars.


7.1 Astrometry

105

Meteor Videos Total S tar - F ilter astro - F ilter P ointing - F ilter

Cam-2.2 908 471 370 318

Cam-2.9 224 111 99 80

Table 7.2: Filtering of Cam-2.2 and Cam-2.9 data according to the different criteria.

Figure 7.7: Distribution of the numb er of stars detected in Cam-3.3 meteor videos.

7.1.3

Cam-3

Figure 7.7 shows the distribution of the numb er of stars detected by Cam-3.3. The numb er of stars detected is comparable to that of Cam-2.2 since the cameras are employ identical optics. The S tar - F ilter criterion for this camera is also set to 10. Inevitably, using fewer stars will cause larger uncertainties in the transformation parameters.


7.1 Astrometry

106

Figure 7.8: Cam-3.3.

Distribution of Astrometric transformation uncertainty

astr o

for

The distribution of the meteor videos with
astr o

astr o

for Cam-3.3 is shown in Fig. 7.8. There were 83
astr o

> 1.0 not shown in this plot. The

distribution is very

similar to that of Cam-2.2, if not slightly worse, since the sharp drop starts at 0.4 pixels.
astr o

- F ilter of 0.5 pixels is used as for Cam-2.2.

The p ointings for Cam-3.3 are shown in Fig 7.9. The camera is p ointed at azimuth = 155.33±0.39 and altitude = 60.15 ±0.10 . The standard deviation of these p ointings suggests that the transformation quality is b etter compared to that of Cam-2.2. Cam-3.9 shows similar results to Cam-3.3. The p ointings calculated were azimuth = 155.37±0.55 and altitude = 60.17 ±0.13 . Since the data is more concentrated than in Cam-2.2, a smaller P ointing - F ilter criterion was used. Meteors that produced p ointing difference of more than ±0.5 and ±0.2 in azimuth and altitude resp ectively from the mean p ointing were filtered out. The filtering of the Cam-3.3 and Cam-3.9 videos are shown in Table 7.3. Ab out 40% of the total meteor videos are filtered out by the S tar - F ilter criterion. Astrometric transformations were computed for 73% of the filtered data. The meteor


7.1 Astrometry

107

Figure 7.9: The p ointing of Cam-3.3. Meteor Videos Total S tar - F ilter astro - F ilter P ointing - F ilter Cam-3.3 875 498 414 360 Cam-3.9 278 184 159 142

Table 7.3: Filtering of Cam-3.3 and Cam-3.9 data according to the different criteria. records filtered out by the S tar - F ilter is primarily due to insufficient stars in the meteor records, and is due to the limitation of the videos of AOMD. But the meteor videos filtered out by the other two filters are due to the limitations of the software. Those meteor videos which were filtered out use the transformation parameter from the last acceptable meteor record previous to it.

7.1.4

Cam-4

Figure 7.10 shows the distribution of numb er of stars detected by Cam-4. Apart from the Gamma/AGC settings, all other settings of Cam-4 are identical with Cam-1. The numb er of meteor records with more than 15 stars is larger compared to Cam-1,


7.1 Astrometry

108

Figure 7.10: Distribution of the numb er of stars detected in Cam-4 meteor videos. Cam-2, and Cam-3. This is due to the fact that Cam-4 recorded twice as many meteors as Cam-1 in the same p eriod of time. A value of the S tar - F ilter criterion of 20 is chosen for this camera, as there are plenty of meteor videos to compute the astrometric transformation accurately. The distribution of at
astr o astr o

for Cam-4 is shown in Fig. 7.11. There is a sharp drop
astr o

0.3 pixels, even though there are many videos with large

, including

306 meteors which have values greater than 1.0 pixels and are not shown in this plot. However, there will b e sufficient videos even with a severe constraint for at 0.3 pixels. The p ointing for Cam-4 is shown in Fig 7.12. Unlike the previous three cameras, here we see six different p ointing clusters. The station in Bangor was shifted once as the amateur astronomer moved home (alb eit only a few blocks away). The camera p ointing apparently changed several times as shown by this figure. Hence, a manual transformation for each of the six different p ointings had to b e calculated. The filtering of the Cam-4 videos is shown in Table 7.3. Since there were 2674
astr o

- F ilter


7.1 Astrometry

109

Figure 7.11: Cam-4.

Distribution of Astrometric transformation uncertainty

astr o

for

Meteor Videos Total S tar - F ilter astro - F ilter P ointing - F ilter

Cam-4 2674 1231 721 718

Table 7.4: Filtering of Cam-4 data according to the different criteria. meteor records, high values of the S tar - F ilter (containing more than 20 stars) and
astr o

- F ilter (less than 0.3 pixels) criteria were used. This reduced the numb er of

meteor records by 53% and 20% resp ectively. Since the meteor videos were already filtered well, only 3 videos were filtered out by the P ointing -F ilter criteria. 718 meteor records are used to compute the astrometric transformations which is comparable to the numb er of meteor records used for other cameras. But the quality of meteor records


7.1 Astrometry

110

Figure 7.12: The p ointing of Cam-4. used is b etter as more severe constraints were used compared to the other three cameras. In conclusion, the uncertainties of the astrometric transformations largely dep end on the numb er of stars available for the computation. Meteor videos captured by Cam-4 enjoy the highest quality of astrometric transformation mainly due to the large numb er of available videos. The transformation of meteors captured by Cam-1 is almost as good as those by Cam-4. The cameras with wide angle optics Cam-2 and Cam-3 have comparatively larger astrometric uncertainties, esp ecially Cam-2, whose results should b e analysed with caution.


7.2 Photometry

111

7.2

Photometry

The photometric calibration of the meteors was done using a crude transformation without any correction for atmospheric extinction. The instrumental magnitudes were transformed into the Johnson V-magnitude as describ ed in Section 5.8. The transformation was done for those videos that had at least 5 stars. This filtering of meteor record based on the numb er of stars for photometry is termed P hoto - f ilter . The of the residuals of the photometric transformation is termed
photo

.

Figure 7.13: The distribution of

photo

of photometric transformation of Cam-2.
photo

Figures 7.13 and 7.14 show the distribution of sp ectively. The p eak at
photo

for Cam-2 and Cam-4 re-

= 0.0 magnitude shows that these meteors were not used

for photometric calibration b ecause they had less than 5 stars; there were 389 and 537 such meteor videos for Cam-2 and Cam-4 resp ectively. The results for Cam-1 and Cam-3 were similar and not shown here. The results from all four cameras are shown in Table 7.5. The P hoto - f ilter in the table refers to the numb er of videos that have more than 5 stars. The mean values of similar to eachother.
photo

are shown for each camera, and are very


7.2 Photometry

112

Figure 7.14: The distribution of Meteor Videos Total P hoto - f ilter photo /Mag.

photo

of photometric transformation of Cam-4. Cam-3 1153 823 0.21±0.04 Cam-4 2674 2137 0.20±0.04

Cam-1 1616 1243 0.23±0.04

Cam-2 1132 743 0.20±0.04

Table 7.5: Filtering of Cam-4 data. Including all the four cameras, ab out 70% of the total videos had more than 5 stars, and thus were photometrically reduced. The mean maximum value of
photo photo

is 0.21 magnitudes and the

is < 0.5 magnitudes. This is a very good result considering

the fact that this is a crude calibration without any photometric corrections. The maximum (b old line) and minimum (dashed line) magnitude distribution of meteors observed by Cam-1 is shown in Fig. 7.15. The minimum magnitude is the brightest value of the meteor while the maximum magnitude is the faintest value of the meteor. Only the meteors that were photometrically reduced were used in this distribution. The brightest meteor observed is of -2.5 magnitude while the faintest meteor observed is +5.8 magnitude. Figure 7.16 shows the maximum (b old) and minimum (dashed) magnitude distribution for Cam-2. The p eak of the minimum magnitude


7.3 Meteor Detection

113

Figure 7.15: Distribution of minimum (dashed line) and maximum (b old line) magnitude of meteors observed by Cam-1. is at +3 magnitude, compared to +4 magnitude for Cam-1, as the wide angle field of view detects brighter meteors. The distribution for Cam-3 is similar to that of Cam-2. However, Cam-4 detected meteors from -6.2 to +6.1 magnitude as shown in Fig 7.17. This is p erhaps due to the different AGC/gamma settings for the camera. It is probably also the reason why Cam-4 has twice the numb er of meteors compared to the cameras from Armagh Observatory.

7.3

Meteor Detection

The meteor detection module is the most imp ortant part of the whole software b ecause if it fails to detect any meteor, then there is no use for the other modules. Finding the centre of the meteor with precision is also very imp ortant in determining the uncertainties of the radiants, the velocities and the orbital elements. The uncertainty in meteor centroiding can b e assessed by
met

, the standard deviation of the residuals of

the p oints from the b est fit line along the path of the meteor.


7.3 Meteor Detection

114

Figure 7.16: Distribution of minimum (dashed line) and maximum (b old line) magnitude of meteors observed by Cam-2.

Figure 7.17: Distribution of minimum (dashed line) and maximum (b old line) magnitude of meteors observed by Cam-4. The distribution of with
met met

for Cam-1 is shown in Fig. 7.18. There were 45 meteors

>3.0 pixels not shown on this plot, as some of the values are higher than 100
met

pixels. The value of

for the ma jority of the meteors is b elow 0.5 pixels.

The results for the other cameras are shown in Table 7.6. The "Detected" row


7.3 Meteor Detection

115

Figure 7.18: Distribution of Meteor Videos Total Detected met <3.0 /pixels met Median/pixels Cam-1 1616 1559 1514 0.30

met

for Cam-1. Cam-3 1153 1119 1086 0.31 Cam-4 2674 2427 2290 0.29

Cam-2 1132 1090 1024 0.22

Table 7.6: Meteor detection. shows the numb er of videos where a meteor was detected. The AOMD database is sorted from other videos such as lighting, aeroplane, birds, flashes etc. through manual insp ection on a daily basis. It is still p ossible, however, that some videos do not contain meteors. Secondly, if there are two meteors, or a meteor and another moving ob ject such as bird or aeroplane, then the meteor detection module fails. The meteors were detected in 95% of the total AOMD videos by SPARVM. Only 4% of these meteors have
met

>3.0 pixels, and thus 90% of the total meteors captured over the p eriod
met

of 2.5 years by all cameras were centroided with a median

of only 0.30 pixels.


7.4 Double Station Data

116

This is the most imp ortant achievement of the software, with resp ect to the scientific utilisation of the data.

Figure 7.19: Distribution of frame numb er p er meteor in Cam-1. Figure 7.19 shows the distribution of the numb er of frames where meteors have b een detected in Cam-1. The sharp cutoff at 3 frames suggests that SPARVM is only able to detect a meteor if it is in 3 or more frames. There is a large numb er of meteor records containing only 3-10 frames. There were 4 meteors with >50 frames. The case was similar for the other cameras. The numb er of frames is related to the duration of the meteors, with the ma jority of the meteors captured by Cam-1 lasting for less than 1 second.

7.4

Double Station Data

SPARVM reduced 386, 148 and 158 double station meteors observed b etween Cam-1 and Cam-4, Cam-2 and Cam-4 and Cam-3 and Cam-4 resp ectively. The double


7.4 Double Station Data

117

station meteors from the different cameras were matched using the time of occurrence of the meteors. In some cases, even if two meteors occurred at the same time, they were not double station meteors. These meteors were filtered out by using the velocity as a discriminator. Non-double station meteor solutions give velocities outside the range 12.0 - 80.0 km s
-1

. An upp er b ound of 80.0 km s-1 , instead of the maximum p ossible
-1

velocity of 72.5 km s

, is used to allow for some uncertainty. It was not p ossible to

use the lower b ound of velocity lower than 12.0 km s-1 in the same way, as the velocity would b e less than the escap e velocity of the Earth. The results of the double station and orbital computation are the p osition of the radiant (R.A., Dec.), V (for b oth stations), and the orbital elements qo , a, e, i, , , and Mo . It is imp ortant to test and verify these results obtained by SPARVM, as well as understand their uncertainties. One way to test the double station results is by comparing the velocity differences as observed from the two stations. In Section 6.4, we saw that the mean of the velocity differences b etween the two stations was 5 km s
-1

, with the maximum difference b eing over 50 km s

-1

.

The V distribution of the meteors observed b etween Cam-4 and Cam-1, Cam-2, and Cam-3 are shown in Fig. 7.20. The stepp ed curve with a maximum at 150 corresp onds to Cam-1, the b old curve with a maximum at 40 corresp onds to Cam-2 and the dashed curve with a maximum of 50 corresp onds to Cam-3. There were 7, 10 and 6 meteors outside the range of this plot for Cam-1, Cam-2 and Cam-3 resp ectively. The maximum difference in V computed was 26.8 km s km s
-1 -1

, 53.2 km s

-1

and 60.7

for Cam-1, Cam-2 and Cam-3 resp ectively. The median values of V for
-1

Cam-1, Cam-2 and Cam-3 are 1.0 km s Cam-1 are accurate to 2 km s these cameras is excellent.
-1

, 1.2 km s

-1

and 1.7 km s

-1

resp ectively.

So we can say in general that the double station velocities computed for meteors in and those in Cam-2 and Cam-3 to 3 km s
-1

. Such

accuracy obtained after analysing more than 600 double station meteors observed by

A change in p osition of the meteor was imp osed to see the resulting change in


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118

Figure 7.20: V difference b etween (i) Cam-1 and Cam-4 (steps),(ii) Cam-2 and Cam-4 (b old line), and (iii) Cam-3 and Cam-4 (dashed line). velocity and radiant for the example meteor used in Section 5.7. The error propagation for observed velocities (V1 and V2) is shown in Fig. 7.21. The X axis shows the change in the p ositions of the meteor centre in the X and Z direction, and the corresp onding change in the velocities is shown on the Y axis. It is interesting that V1 and V2 change in such a way that the average of the two remains the same. This shows that the uncertainties in the p osition of the meteor centre have little effect on the average velocity computed from the two stations. But the differences of velocity computed from the two stations increase with the change in meteor p osition, resulting to ab out 30 km


7.4 Double Station Data

119

Figure 7.21: Error propagation in the velocities (V1 and V2) observed from two stations. s
-1

difference for the change of 20 pixels in X and Z directions. The uncertainty in the

p osition of most of the meteors is ab out 1.0 pixels, causing a velocity uncertainty of ab out 1.5 km s
-1

.

Error propagation for the p osition of the radiant (R.A. and Dec.) is shown in Fig. 7.22. A change in the X and the Z direction of the meteor centre by 1 pixel causes the R.A. and Dec. to change by 0.4 and 0.2 resp ectively. The change is not symmetric for b oth R.A and Dec. on either side of the X and Z direction. These results only give an indication of uncertainties in velocities and the radiant for this particular meteor. There are alternative ways to assess the uncertainties in these parameters, such as by comparing the results from meteors observed by more than two cameras. 87 double station meteors were observed by b oth Cam-1 and Cam-3, whereas 76 double station meteors were observed by b oth Cam-1 and Cam-2. Only 14 double station meteors


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120

Figure 7.22: Error propagation in the p osition of the radiant (R.A. and Dec.). were observed by b oth Cam-2 and Cam-3. Since they observe the same meteor, the radiant and the velocities of these meteors computed by different combinations of the cameras should yield the same result. Some minimal difference should b e exp ected eg. due to the difference in the angular pixel size of the cameras. Figure 7.23 shows the difference of radiant for the double station meteors observed by b oth Cam-1 and Cam-3. The b old line and the dashed line show the difference in R.A and Dec. resp ectively. There were 6 meteors for R.A. and 2 for Dec. which were outside the given range and are not shown on this plot. The median difference in R.A. and Dec. are 0.69 and 0.38 resp ectively. Out of the total 87 meteors, 76 of these meteors have differences in R.A. of less than 3 , and 83 of them have differences in Dec. of less than 3 . This shows that the radiant estimates, b oth in R.A. and Dec., computed by Cam-1 agree with those from Cam-3. The differences in V of the double station meteors observed by b oth Cam-1 and


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121

Figure 7.23: Difference of radiant, R.A. (b old line) and Dec. (dashed line), for meteors observed by Cam-1 and Cam-3. Cam-3 are shown in Fig 7.24. There were 2 p oints not shown in this plot as they lie outside the given range. The median difference in V is only 0.89 km s meteors (out of 87) having less than 3 km s
-1 -1

with 70

difference. This shows the agreement of

V b etween the meteors observed by the two cameras. The comparison of double station meteors observed by b oth Cam-1 and Cam-2 show much larger differences. The distribution of the difference in radiant for the double station meteors observed by b oth Cam-1 and Cam-3 is shown in Fig. 7.25. The b old line and the dashed line show the difference in R.A and Dec. resp ectively. There were 1 meteors for R.A. and 3 for Dec. which were outside the given range and are not shown on this plot. Out of the total 76 double station meteors, 55 meteors have a difference of less than 3 in R.A, and 57 meteors in Dec. The median difference in R.A. and Dec. is


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122

Figure 7.24: Difference in V for meteors observed by Cam-1 and Cam-3. 1.18 and 1.30 resp ectively, almost twice (0.69 and 0.38 ) compared to the difference b etween Cam-1 and Cam-3. The differences in V of the double station meteors observed by b oth Cam-1 and Cam-2 are shown in Fig 7.26. There were 4 p oints not shown in this plot as they lie outside the given range. The median difference in V is 1.57 km s twice the difference b etween Cam-1 and Cam-3 (0.89 km s 76) have less than 3 km s
-1 -1 -1

which is almost

). 52 meteors (out of

difference in V .
-1

The meteors with difference of less than 3 km s

in V and less than 3 in R.A. and

Dec. of the radiant are taken as having good agreement. Overall there was agreement for 70% of the meteors observed by b oth Cam-1 and Cam-2. This is less compared to the agreement of 80% of the meteors observed by b oth Cam-1 and Cam-3. The biggest difference was in Dec. of the radiant, where 75% of the meteors observed by b oth Cam-1 and Cam-2 were in agreement compared to 95% of the meteors


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123

Figure 7.25: Difference of radiant, R.A. (b old) and Dec. (dash), for meteors observed by Cam-1 and Cam-2. b etween Cam-1 and Cam-3. The large uncertainties in the results of meteors observed by Cam-2 is mainly due to astrometry, as can b e seen in Section 7.1.2. It might b e p ossible to increase the agreement b etween the meteors observed by b oth Cam-1 and Cam-2 by re-calculating the astrometric transformation with different constraints. The double station meteors from Cam-1 and Cam-3 are compiled into a catalogue of meteors as shown in App endix B. The catalogue includes unique ID, date and time of meteor occurrence (in Cam-1 and Cam-3), R.A. and Dec. of the radiant, V as observed by Armagh and Bangor, and finally the orbital elements qo , a, e, i, , and Mo . The meteors from Cam-2 were not included in the lists, as the astrometric precision requires further improvement to reach the same level of precision as the results obtained from the meteors observed by the other two cameras. The meteors observed by b oth Cam-1 and Cam-3 are denoted by " * " in the ID, and all the results are mean of the result computed from two different cameras combination (ie Cam-1/Cam-4 and


7.4 Double Station Data

124

Figure 7.26: Difference of V for meteors observed by Cam-1 and Cam-2. Cam-3/Cam-4) . The radiant and velocities of the double station meteors from this catalogue are shown in Figs. 7.27 - 7.33. The R.A. is shown in Y-axis, Dec. in X-axis and the velocities are indicated by colours. One of the obvious conclusions derived from these figures is that most of the meteors are sp oradics and are spread out in radiant and velocity compared to the shower meteors which are clustered together. Fig 7.29 (month of August) shows a big gap in the middle with very few meteors. This is b ecause of the p osition of the Sun. The Sun is located b etween R.A.130 , Dec. +18 (1st Aug.) and R.A.159 , Dec. +8.6 (31st Aug.) in the month of August. Similar gaps can b e seen in Figs. 7.30 - 7.33. The p osition of the Sun on other months are Septemb er (R.A.172 , Dec. +3 ) , Octob er (R.A.200 , Dec. -8 ), Novemb er(R.A.230 , Dec. -18 ) and Decemb er (R.A.262 , Dec. -23 ).


7.4 Double Station Data

125

Figure 7.27: Double station meteors for the months of Jan-Mar. A ma jor meteor shower in this plot is the Quadrantids (QUA; R.A.= 230 , Dec = +49 , V = 41 km s -1 )


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126

Figure 7.28: Double station meteors for the months of Apr-Jul. A ma jor meteor shower in this plot is the Perseids (PER; R.A.= 46 , Dec = +58 , V = 59 km s-1 )


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127

Figure 7.29: Double station meteors for August. A ma jor meteor shower in this plot is the Perseids (PER; R.A.= 46 , Dec = +58 , V = 59 km s-1 )


7.4 Double Station Data

128

Figure 7.30: Double station meteors for Septemb er.


7.4 Double Station Data

129

Figure 7.31: Double station meteors for Octob er. Ma jor meteor showers in this plot are the Orionids (R.A.= 95 , Dec = +16 , V = 66 km s-1 ), Northern Taurids (R.A.= 58 , Dec = +22 , V = 29 km s-1 ) and Southern Taurids (STA; R.A.= 52 , Dec = +13 , V = 27 km s-1 )


7.4 Double Station Data

130

Figure 7.32: Double station meteors for Novemb er. Ma jor meteor showers in this plot are the Leonids (LEO; R.A.= 153 , Dec = +22 , V = 71 km s-1 ), Northern Taurids (NTA; R.A.= 58 , Dec = +22 , V = 29 km s-1 ) and Southern Taurids (STA; R.A.= 52 , Dec = +13 , V = 27 km s-1 )


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131

Figure 7.33: Double station meteors for Decemb er. Ma jor meteor showers in this plot are the Geminids (R.A.= 112 , Dec = +33 , V = 35 km s-1 ), Ursids (R.A.= 217 , Dec = +76 , V = 33 km s-1 )


7.5 Geminids

132

7.5

Geminids

Figure 7.33 shows the double station meteors for the month of Decemb er, which is one of the more active months with regard to meteor showers, including the Ursids, -Orionids, Decemb er Monocerotids to name a few. The Geminids are denoted by the sky blue cluster (Velocity = 30-35 km s
-1

) at approximately R.A. = 110 and Dec =

33 . There were 9, 6, and 10 (total of 25) double station Geminids observed during the year 2005, 2006 and 2007 resp ectively. The date for these Geminids ranges from 12-15 Decemb er for all three years.

Figure 7.34: V distribution for Geminids. The distribution of the V estimates is shown in Fig. 7.34. More than 80% of the Geminids have V b etween 30 and 34 km s
-1

. The p eak V is 32 km s
-1

-1

which

is slightly less compared to the IMO values (35 km s

). The mean of V computed
-1

from each station individually are 31.7 km s-1 and 32.3 km s

for Armagh and Bangor

stations resp ectively, which shows the velocity agreement b etween the two stations. The


7.5 Geminids
-1

133

geocentric velocities Vg ranges from 32.5 - 34.6 km s

as compiled from various sources

(in Table 7) by Jenniskens (2006). The range of velocities of Geminids might b e one of the p ossible reason for a difference of 3 km s R.A. (deg) 111.9±1.8 112
-1

compared with the IMO values. V (km s-1 ) 32.0±1.6 35

Observed IMO

Dec.(deg) +33.4±1.0 +33

Table 7.7: Radiant and V of Geminids.

Figure 7.35: Radiant drift of Geminids. Y axis shows R.A. - 100 and Dec. denoted by + and resp ectively. X-axis shows the normalised time. The mean of the observed R.A. and Dec. of the radiant and the V are compared with the results obtained from the 2005 IMO calendar
26

as shown in Table 7.7. The

R.A. and Dec. of the radiant are in very good agreement with those from the IMO calendar. The comparably high standard deviations in R.A. and Dec. is due to the radiant drift.
26

http://www.imo.net/calendar/2007


7.6 Finding parent ob jects

134

Figure 7.35 shows the 9 Geminids observed during the year 2005. The R.A.-100 and Dec., denotes by and +, are shown in Y-axis in degrees. The X-axis shows the normalised time in days (with the first detected Geminid as Time = 0.0). Out of the 9 Geminids, 7 were observed in one night and 2 on the second night. The drift in the radiant is not obvious from this Fig. A regression fit estimates
D ec t R.A. t

= 2.4 /day and

= -0.40 /day. Given the small size of the sample, the trend of the drift agrees
R.A. t

with

= 1.0 /day and

D ec t

= -0.15 /day as given by Jenniskens (2006). e 0.863±0.02 0.889 i (deg) 21.7±3 22.1 (deg) 260.7±1 265.3 (deg) 324.4±1 322.0

Geminids 3200 Phaethon

qo (AU) 0.159±0.01 0.139

Table 7.8: Orbital elements of Geminids and 3200 Phaethon. The median values of the orbital elements of the 25 Geminids are compared to its parent 3200 Phaethon (JPL Small-Body Database27 ) in Table 7.8. There is a good agreement b etween the orbital elements of the Geminid meteor shower computed by SPARVM and Phaethon in the p erihelion distance (qo ), eccentricity (e) and inclination (i), the longitude of ascending node () and argument of p erihelion ( ).

7.6

Finding parent ob jects

Established meteor showers from the IAU meteor database with an unknown or unverified parent were searched among the meteors from the catalogue of double station meteors. The meteors were identified as shower meteors dep ending on their radiant, velocity and time of occurrence. Out of the total 22 meteor showers searched, there was a single meteor identified as a South -Aquariid, -Cygnids, -Virginids, Dec. Leonis Minorids, Nov. Orionids and 3 meteors identified as -Hydrids. Comets from "Catalogue of Cometary Orbits" (Marsden & Williams, 2008) were
27

http://ssd.jpl.nasa.gov/sb db.cgi#top


7.6 Finding parent ob jects qo (AU) South -Aquariid C/1733 K1 C/1816 B1 C/1961 O1 -Cygnid 2008 ED69 2001 MG1 2004 LA12 177P -Hydrids#1 -Hydrids#2 -Hydrids#3 C/1787 G1 C/1902 R1 -Virginid 1998 SH2 Dec. Leonis Minorid C/1959 Y1 Nov. Orionid C/1743 X1 C/1917 F1 0.0729 0.1029 0.0485 0.0401 0.9933 0.7224 0.8932 0.6332 1.1077 0.2297 0.2219 0.2467 0.3489 0.4010 0.7168 0.7601 0.5316 0.5043 0.1170 0.2222 0.1901 e 0.9728 1.0 1.0 0.9999 0.6793 0.7496 0.6433 0.7478 0.9541 0.9608 0.9839 0.9664 1.0 0.9999 0.6348 0.7188 0.8495 1.0001 0.9728 1.0 0.9931 i (deg) 28.2 23.7 43.1 24.2 33.2 36.2 28.4 39.4 31.1 126.9 124.5 124.6 131.7 156.3 0.6 2.4 131.6 159.6 24.7 47.1 32.6 (deg) 300.8 271.0 325.8 98.9 147.0 149.8 142.4 159.2 60.2 80.0 81.1 78.9 109.8 50.7 14.4 14.2 260.0 252.6 64.7 49.2 88.6 (deg) 151.6 187.8 304.3 270.7 190.4 172.7 218.3 199.4 272.2 124.9 124.8 122.8 99.1 152.9 254.7 259.9 271.6 306.6 142.2 151.4 121.3

135

Table 7.9: Orbital elements of established shower with unknown or unsure parent ob jects compared with those of p ossible parents. searched for p ossible associations with these meteor shower. The orbital elements of some of the asteroids (from JPL Small-b ody database) are also compared. Table 7.9 compares the orbital elements of these meteoroids with those of their p ossible parent comets. The South -Aquariids have an orbit similar to that of C/1733 K1 in qo , e and i but differ by ab out 30 in b oth and . The -Cygnids have b een associated with 2008 ED69 by Jenniskens & Vaubaillon (2008). The shower is further studied by Trigo-Rodriguez et al. (2009) concluding that more observational data and studies of the physical parameters are needed b efore


7.6 Finding parent ob jects

136

excluding 2001 MG1 and 2004 LA12, as parents of the -Cygnid stream. Tikhomirova (2007) suggests that comet 177P is the parent of the -Cygnids. Identification of the parent of the -Cygnid is not obvious from this comparison, as more data is needed such as the spread of the meteor stream in any particular direction. The orbits of the 3 -Hydrids are compared with C/1787 G1 and C/1902 R1. Only some of the orbital parameters are in agreement. So these two ob jects seem to b e unlikely parents for the -Hydrids. A suitable candidate might b e found if the search is extended to ob jects other than comets. Christou (2004) indicated the p ossibility of 1998 SH2 as the parent ob ject of Virginids. One double station -Virginid was observed on 2007/04/05 at 01:00:09 UT. The meteor emanated from a radiant of R.A. = 187.3 and Dec. = 3.26 with V = 17.4±2.3 km s
-1

. The orbital elements of the -Virginids is in good agreement with

that of the asteroid 1998 SH2 as shown in Table 7.9. Thus, 1998 SH2 is a p ossible parent ob ject of the -Virginids. Only orbital similarity is not sufficient to relate meteor streams with their parent ob jects. Due to large numb er of NEOs discovered, the probability of two orbits b eing similar at the present time by coincidence is high. So more methods such as investigation of the evolution of the orbits (Poruban et al., 2004) or comparison of the physical c prop erties of the ob ject and the meteoroid stream (Jewitt & Hsieh, 2006) is required to fully confirm a parent ob ject. Some elements of the orbit of Dec. Leonis Minorids are similar to those of C/1959 Y1. Similarly, C/1743 X1 and C/1917 F1 (the later also the parent of the Decemb er Monocerotids) are p ossible candidates for the parent of the Nov. Orionids.


Chapter 8

The 2007 Aurigid outburst

8.1

Intro duction

The -Aurigid annual shower is one of the less active showers, and occurs from ab out 25th August to 8th Septemb er every year. The maximum activity occurs at solar longitude = 158.6 (31st Aug. - 1st Sep.). Though the Zenithal Hourly Rate (ZHR) is only 7, the p opulation index r = 2.6 and velocity at infinity V = 66 km s & Arlt, 2002) produces bright and fast meteors. The -Aurigid shower is so named b ecause the meteors emanate from a radiant near the star Cap ella ( Aurigae). Cap ella is the brightest star in this constellation. There exist additional Aurigid showers, namely - Aurigids, - Aurigids, - Aurigids etc. where meteors radiate from the , , stars resp ectively. The - Aurigids have a known parent comet called C/1911 N1 (Kiess). Long p eriod comet Kiess, which was discovered in July 1911 (Kiess et al., 1911), has a near parab olic orbit and takes more than 2000 years to complete one revolution around the Sun. Very little is known ab out the comet itself as it was observed for only 71 days.
-1

(Dubietis

137


8.1 Introduction 1994 Date Time [UT] FWHM (min) ZHR R.A. (J2000) Dec. (J200) Sep. 01 7:54 30 200±25 +1.13 1986 Sep. 01 01:22 28±7 200±25 90.5 +34.6 +0.54 1935 Sep. 01 03:04 31±13 100 86.3 +40.5 +2.62

138

Table 8.1: Past Aurigid Outbursts

8.1.1

Past Aurigid Outbursts

Outbursts of the Aurigid shower were observed visually by chance in 1935 (Teichgraeb er, 1935; Guth, 1936), 1986 (Tepliczky, 1987) and 1994 (Zay & Lunsford, 1994). Table 8.1 shows the date, time, full width at half maximum (FWHM) of the outburst profile, Right Ascension (R.A.) and Declination (Dec.) of the radiant, and the average magnitude of the Aurigids observed (Jenniskens & Vaubaillon, 2007a). All these outbursts had ZHR greater than 100, and were rich in bright meteors. The FWHM of the outburst was 30 minutes. Zay & Lunsford (1994) describ ed the 1994 Aurigids as having greenish or bluish colour, p erhaps due to strong iron and magnesium ablation, which in turn would suggest different particle morphology compared to the annual Aurigid shower. It is imp ortant to note that these three outbursts were observed by chance, and thus no detailed information has b een recorded. All the observations were visual, carried out by a few observers. Even though there is no doubt ab out the occurrence of these outbursts, these results might have large uncertainties given the circumstances and the observing methods used.


8.1 Introduction

139

8.1.2

Prediction for the 2007 Outburst

The recent model by Jenniskens & Vaubaillon (2007a), hereafter referred to as JVa, reproduced all these past outbursts (1935, 1986 and 1994) and, in addition, predicted one on 1st Septemb er 2007. The model used 1,000,000 meteoroids ejected from the comet's back-pro jected p erihelion passage in 80 BC and tracked their evolution in time. Although there is some uncertainty in the orbit of this comet, the precise p osition of the dust trail is not sensitive to the adopted p erihelion time since planetary p erturbations occur only on the inward leg of the orbit (JVa). 2007 Aurigid outburst Date Peak time FWHM ZHR R.A. Dec. Velocity 1st Septemb er 2007 11:36±20 UT 0.42 h 200±25 92 +39 67 km s-1

Table 8.2: Prediction made for 2007 Aurigid outburst by Jenniskens & Vaubaillon (2007a) Figure 8.1 shows the p osition of the nodes of the 1-revolution Aurigid meteoroids (JVa, 2007). The dots on the plot are meteoroids at the moment of passing through the ecliptic plane, and the line passing through is the Earth's orbit. Table 8.2 shows the predictions made for the 2007 -Aurigid outburst. The model predicted a p eak time of 11:36±20 min UT, b est seen from locations in Mexico, and the western parts of Canada and the United States. The modelled time for the p eak is 1, 16 and 7 minutes earlier for the outbursts in 1994, 1986 and 1935 resp ectively. So, the prediction made in advance of the 2007 outburst carried with it an uncertainty of ab out 20 minutes. The shower was predicted to last ab out 1.5 hours, reaching a p eak Zenithal Hourly Rate (ZHR) of 200 over a short (10-minute) interval. The meteors were predicted to emanate with a sp eed of 67 km s
-1

from a radiant at Right Ascension (R.A.) =


8.1 Introduction

140

Figure 8.1: Position of the node of the model 1-revolution Aurigid stream particle trail. Source: Jenniskens & Vaubaillon (2007a) 92 and Declination (Dec.) = +39 (J2000). Like past Aurigid outbursts, this one was predicted to b e rich in bright, -3 to +3 magnitude, meteors with few faint ones. This is the first prediction made prior to a meteor outburst due to dust ejected from a known long p eriod comet.


8.2 Observations

141

8.1.3

Scientific significance

Very little scientific information was recorded during the past Aurigid outbursts. The outburst in 2007 provided the opp ortunity to use modern instruments to gather a wide range of data p ertaining to the physical and dynamical prop erties of a long-p eriod comet and its constituent matter. Only one outburst from a long p eriod comet's dust trail, that of the -Monocerotids in 1995, has b een observed by modern instruments (Jenniskens et al., 1997). These meteoroids, whose parent ob ject is still unknown, were found to b e low in volatile elements such as sodium (Borovika et al., 2002), compared to the meteoroids from c short p eriod comets. One p ossible hyp othesis is that b ecause of the infrequent visit of long p eriod comets to the inner solar system, the meteoroids ejected from these comets could originate from their pristine crusts, p ossibly exp osed to cosmic rays in the Oort cloud (Jenniskens et al., 1997). Thus, Aurigid meteoroids detected in 2007 could provide us with new information on the prop erties of long p eriod comets and their surroundings.

8.2

Observations

We (Atreya & Christou, 2009) observed the 2007 Aurigid outburst from San Francisco, USA, as part of the observation campaign organised by Dr. Peter Jenniskens (NASA Ames Research Centre, USA). Two observing stations were set up, one at Fremont Peak and the other at Lick Observatory, 68 km apart, suitable for double station observations. Table 8.3 shows the latitude, longitude and altitude of these two locations. Fig. 8.2 shows a schematic of the double station geometry from these two locations in California. Two WaTec 902DM2s video cameras were used, which are similar to the ones op erating in Armagh Observatory (Atreya & Christou, 2008). The cameras were connected


8.2 Observations

142

Figure 8.2: Schematic of double station setup in California.

Latitude Longitude Altitude

Fremont Peak Observatory 36 45 N 121 29 W 900 m

Lick Observatory 37 21 N 121 38 W 1283 m

Table 8.3: Observing station in California.

with a laptop computer and meteors were recorded using the UFO Capture V2.0 software29 . In addition two camcorders, equipp ed with image intensifiers, were provided by the organiser to op erate from Lick Observatory. The group at Fremont Peak was joined by a team from Germany (Bernd Brinkmann & Daniel Fisher) with two Mintron cameras and using the software package Metrec (Molau, 1999) to record meteors. The sp ecific details of all the cameras are listed in Table 8.4. Hereafter, the ID (first column) will b e used to denote the sp ecific cameras. Figure 8.3 (i) shows an example of an Aurigid observed at 11:30:01 UT by Watec Camera (Cam-5) from Lick Observatory. Similarly, Fig. 8.3 (ii) shows an Aurigid at 11:04:36 UT observed by camcorder with image intensifier (ICAMSW) at Lick Observatory and Fig. 8.3 (iii) shows an example of an Aurigid observed at 12:02:40 from Lick Observatory by Mintron camera (Bernd). The use of different typ es of cameras
29

http://sonotaco.com/e index.html


8.3 Data Reduction

143

ID Fremont Peak Cam-5 Daniel Bernd Lick Observatory Cam-6 ICAMSE ICAMSW

Model

& Lens

FOV

Software

Watec 902DM2s & f0.8, 8.0 mm Mintron & f0.8, 6.0 mm Mintron & f0.8, 6.0 mm

39 x 27 58 x 40 58 x 40

UFO Capture V2.0 Metrec Metrec

Watec 902DM2s & f0.8, 3.8 mm Image Intensifier + camcorder Image Intensifier + camcorder

82 x 55 30 x 30 30 x 30

UFO Capture V2.0 ­ ­

Table 8.4: Sp ecifications of cameras used at Fremont Peak and Lick Observatory.

and software reduces any biases such as a particular cameras b eing sensitive to faint meteors or systematic errors of the recording and processing software packages. Our observations lasted for more than 3 hours, starting from 9:00 UT until 12:30 UT (ie until 6:30 am local time). The sky was clear, but the gibb ous phase moon was high ( 69 at 11:30 UT). However, the Aurigids were exp ected to b e bright and the cameras were p ointed away from the moon during the exp ected p eak time of the outburst.

8.3

Data Reduction

Meteors from the Mintron cameras were analysed by the German group using Metrec (Molau, 1999). The time, radiant p osition (RA, Dec) and apparent magnitudes were computed by Metrec. The software also distinguished whether single station meteors b elonged to the sp oradic background or to the Aurigids. This information was incorp orated in SPARVM for double station analysis and computation of orbital elements. The sp ectral sensitivity of the image intensified cameras is different than that of the CCD video cameras. The current version of SPARVM is not optimised for photometric reduction of meteors recorded by the image intensified cameras. Hence meteor events


8.3 Data Reduction

144

Figure 8.3: Aurigid observed at (i) 11:30:01 UT from Cam-5, (ii) 11:04:36 UT from ICAMSW and (iii) 12:02:40 UT from Bernd


8.3 Data Reduction

145

recorded by these cameras were not reduced photometrically.

Figure 8.4: Instrumental magnitude of several stars throughout the observing duration at Fremont Peak Figure 8.4 shows the change in instrumental magnitude of stars as a function of altitude at Fremont Peak Observatory (Cam-5). The instrumental magnitude of several stars were calculated during the time of the observation. The relatively straight lines, with variation of only 0.2 mag, show that the observing conditions remained the same throughout the night. It was also surprising that there was little change in the instrumental magnitude of the stars at various altitudes. Generally, the instrumental magnitude of a star b ecomes less bright with a decrease in altitude; as the light has to travel a longer distance through the atmosphere near the horizon compared with the zenith. Similar results was obtained from Lick Observatory. Thus no correction for atmospheric extinction was made. Figure 8.5 shows the relation b etween instrumental and visual magnitude for stars in the meteor videos from Cam-5. The photometric calibration is done separately for


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Figure 8.5: Transformation b etween Instrumental and Visual magnitude each meteor video. A least square line was fitted for 21 stars with an rms of 0.172 mag. Similar values for the rms ( 0.2 mag.) were obtained for other meteors from Cam-5 and Cam-6. Thus, the uncertainty for the photometric transformation was 0.2 mag. Equation 8.1 shows the transformation b etween instrumental magnitude of Cam-5 and Visual magnitude (Optical Johnson V band, 500-600 nm) for a meteor recorded at 07:30:50 UT. The first value (9.660) gives the offset b etween two magnitude systems. Ideally, a change in instrumental magnitude should equal a change in visual magnitude, and thus the slop e of the fit should b e 1.0. However, due to uncertainties, the slop e for this meteor is 0.9228. Similar transformation equations were calculated for other meteors from Cam-5 and Cam-6.

Vmag = 9.660 + 0.9228 I

mag

(8.1)


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Daniel Metrec Cam-5 SPARVM -2 68 0

RA [deg]

Vmag
53 54 55 56 57 58

64 60

2

4 56 0 0.2 0.4 0.6 0.8

Dec [deg]
-2 -2

Time [s]

0

0

Vmag

2

Vmag
53 54 55 56 57 58

2

4

4 56 60 64 68

Dec [deg]

RA [deg]

Figure 8.6: Metrec and SPARVM comparison of p osition and magnitude Figure 8.6 shows the comparison b etween photometric reduction using Metrec and SPARVM software. An Aurigid at 11:30:01 UT was recorded by b oth Daniel and Cam-5 at Fremont Peak. The top left plot compares the b est-fit tra jectories (R.A. and Dec.) of the meteor. The top right plot compares the two Visual magnitude (V profiles. The b ottom two plots compare V R.A., Dec. and V
mag mag mag

)

with resp ect to the R.A. and Dec. The

computed from two different cameras and software agree with


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each other. The difference in time was corrected by overlapping the p eak of the light curve of a numb er of meteors from b oth cameras. The only difference is in V
mag

. at the

b eginning and the end of the light curve, which could not b e accounted for by the 0.2 mag uncertainty. The accuracy of Metrec magnitude is not known. Also interesting to note is that, for this particular case, Metrec observed the Aurigid only down to +3.4 mag, while SPARVM recorded it much fainter, down to +4.6 mag.
0 Cam-5 Cam-6 Bernd Daniel

0.5

Absolute Magnitude

1

1.5

2

2.5

3 18.6

18.62

18.64

18.66

18.68

18.7

18.72

18.74

Time [s]

Figure 8.7: Absolute magnitude comparison b etween four cameras for a meteor recorded at 12:14:18 UT Figure 8.7 compares the absolute magnitude b etween Daniel, Bernd, Cam-5 and Cam-6 for a meteor recorded at 12:14:18 UT. The maximum brightness of all four cameras are within 0.13 mag., which is comparable to the estimated photometric uncertainty of 0.2 mag. However, there are large variations, up to 1.0 mag, b etween the light curves at various times. It is interesting to note the difference b etween Bernd and Daniel, which used the same camera and processing software and were at the same location. Bernd and Cam-5 light curves agree with each other. The light curves of Cam-5 and Cam-6, b oth processed by SPARVM software, shows good agreement for the first three frames. It is imp ortant to note that Cam-6 was located at Lick Observatory, while the other three cameras were located at Fremont Peak. Also, compared


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to all the other cameras, Cam-6 was most affected by moonlight. Moon and ambient sky brightness at the different locations could have resulted in underestimating the brightness of the meteor in the last frame for Cam-6.

8.4
8.4.1

Results
Outburst Profile

Aurigids from Lick Obs. and Fremont Peak Obs.
12 10 min 5 min 10

Number of Aurigids

8 6 4 2 0 10:30 10:40 10:50 11:00 11:10 11:20 11:30 11:40 11:50 12:00

Time [UT]
Figure 8.8: Observed Aurigid counts for 10 min(Red-b old) and 5 min(Green-dashed) interval from Lick and Fremont Peak Observatory. Figure 8.8 shows the Aurigid count combined from all six cameras from b oth stations. The 10 min interval counts shows that the p eak occurred b etween 11:10 - 11:20 UT. Jenniskens & Vaubaillon (2007b) came to a similar conclusion, giving a p eak time of 11:15±5 min UT. Similarly, the visual observers (Rendtel, 2007) observed a p eak time of 11:20±3 min UT. The predicted time for the outburst was 11:36±20 min UT (JVa,


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2007). As the past Aurigid outbursts was observed prior to the modelled prediction, a p eak time of 11:15 UT for the 2007 Aurigid outbursts is consistent with this empirical correction to the model predictions. A p eak of ZHR = 136±26 was computed based on counts over five-minute interval (Rendtel, 2007). Similarly, ZHR 100 was calculated from the airb orne observations (Jenniskens & Vaubaillon, 2007b). Both these ZHR estimates are short of the predicted 200±25. One of the reasons could b e that the Earth did not pass through the exact centre of the dust trail, as the p eak occurred 20 min. prior to the predicted time. However, since the annual -Aurigids have ZHR= 7±1 (Dubietis & Arlt, 2002), the enhancement was very significant.

8.4.2

Radiant and Velocity

There has b een some confusion regarding the radiant of the - and the -Aurigids (Habuda, 2007). The annual Aurigid shower (IAU shower code # 206), or more precisely the -Aurigids, has a radiant at30 R.A. = 84 and Dec. = 42 or R.A. = 85.5 and Dec. = 42 (Cook, 1973). The past Aurigid outbursts app eared from a slightly different radiant referred to as -Aurigids (Jenniskens, 1995). The meteors from these outbursts, including the one in 2007 Septemb er, are known as the -Aurigids, while the annual shower meteors are called -Aurigids. Five double station Aurigids were successfully detected from Lick Observatory and Fremont Peak, from a combined four cameras used by the authors, and two from the German group. Two of the double station Aurigids were also observed with a third camera, thus increasing the confidence in the radiant and orbit solution. The radiant of the observed -Aurigid outburst, annual -Aurigid shower and the predicted radiant for the outburst are shown in Fig. 8.9. The measured values are also shown in Table 8.5 (columns 3-4). The median values for the radiant of the outburst
30

http://www.imo.net


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151

43 Observed -Aurigid Annual -Aurigid Predicted

42

Declination [deg]

41

40

39

38 94 92 90 88 86 84

Right Ascension [deg]
Figure 8.9: Radiant of Observed -Aurigids, the predicted radiant for the outburst, and the annual -Aurigid shower. are R.A.=90.87 and Dec. = +39.00 , with the observed R.A. of the radiant 1 lower than that of the prediction of JVa. Four of the Aurigids seem to form a compact radiant while one of the Aurigids is 1 further apart away, towards the direction of the annual Aurigid radiant. With only 5 p oints, it is difficult to sp eculate on the reason for the outlier. The observational accuracy of the radiant is 0.03 and thus cannot account for it. One p ossibility could b e a slightly diffuse radiant of 2 in diameter. Double station analysis allows the precise computation of meteor p osition and velocity vectors from which their heliocentric orbital elements can b e worked out. Table 8.5 compares the results for the five double station Aurigids with the time of occurrence (in UT), Camera used for Fremont Peak (FP) and Lick Observatory (LO), R.A. and Dec. of the radiant, Velocity at infinity (V1 ) and (V2 ) observed from FP and LO resp ectively, and the annual -Aurigid shower. The Aurigids at 11:30:01 UT and 12:02:40 UT were observed by 3 different cameras, providing an opp ortunity to estimate the confidence in the results produced. The


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152

Time [UT] 10:53:31 10:55:50 11:04:36 11:30:01 12:02:40

FP/LO [deg] Bernd/ICAMSW Bernd/ICAMSW Bernd/ICAMSW Daniel/Cam-6 Cam-5/Cam-6 Bernd/Cam-6 Daniel/Cam-6 -Aurigid

RA [deg] 89.44 90.87 91.44 90.90 90.83 91.13 91.19 85.5 ± ± ± ± ± ± ± 0.03 0.03 0.02 0.11 0.27 0.10 0.10

Dec [km s + + + + + + +

-1

] 0.03 0.03 0.02 0.10 0.06 0.09 0.09

V1 [km s 67.0 65.5 66.7 62.5 63.5 65.3 67.2 66.3

V2
-1

] 67.9 67.5 67.9 65.7 66.2 68.7 68.6 ± ± ± ± ± ± ± 2.4 3.0 2.6 1.7 1.7 3.4 3.4

40.13 39.00 38.84 39.13 39.11 38.97 38.97

± ± ± ± ± ± ±

± ± ± ± ± ± ±

1.4 1.3 0.8 7.6 2.8 7.7 11.8

Annual

+42.0

Table 8.5: Radiant and Velocity of Aurigids difference in RA is 0.07 and in Dec is 0.02 for b oth Aurigids. This shows that the estimation of the radiant is fairly robust. The difference in V1 computed from two different camera pairs is 1.0 km s
-1

(11:30:01) and 1.9 km s

-1

(12:02:40). The
-1

difference b etween the V observed at FP (V1 ) and LO (V2 ) is 1-3 km s

. It

is also imp ortant to p oint out that some of these velocities have large errors, such as the 12:02:40 (Daniel/Cam-6) Aurigid (uncertainty of 11.8 km s-1 for V1 ). The velocities are calculated using each measured p oint along the track of the meteor, and the uncertainties in V are due to the disp ersion of the calculated velocities b etween each observed p oints. The median values for the radiant of the outburst R.A. = 90.87 and Dec = +39.00 were consistent with the prediction. The median V computed (67.0±1.4 km s in good agreement with the predicted value of 67 km s
-1 -1

) was

.

8.4.3

Heights

Table 8.6 shows the time (UT), b eginning height (Hb ), terminal height (He ), height of maximum brightness (Hmax ) and the brightest magnitude MM ax . The Aurigid at 11:04:36 UT exited the field of view while its brightness is still increasing, thus only upp er limits for Hmax and He can b e estimated for this meteor. The Hb quantity


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153

dep ends strongly on the limiting magnitude of the camera and the threshold detection limit of the software. Time [UT] 10:53:31 10:55:50 11:04:36 11:30:01 12:02:40 Hb [km] 120.87 119.90 >112.9 119.95 125.27 He [km] 96.71 97.24 116.46 92.55 94.04 Hmax [km] 100.55 106.72 104.40 100.83 MM
ax

- - + - -

1.0 0.6 0.6 0.6 3.4

Table 8.6: Heights of Aurigids The median values for the b eginning height (Hb =120.87 km), the height of maximum brightness (Hmax =101.40 km) and the terminal height (He =96.71 km) are comparable to those of the Leonids (Hb = 120.0± 3.5 km, H meteor with an MM of -3.4.
max

= 106.9± 3.8 km and He = 96.5± 3.7

km) given in Koten et al. (2004). The Aurigid observed at 12:02:40 is the brightest
ax

The outburst of the -Monocerotids observed in 1995 had meteors which p enetrated 5 km deep er into the atmosphere compared to meteors of the same brightness, velocity and entry angle. It had b een suggested that this was due to the lack of volatile elements such as sodium in the meteoroids (Jenniskens et al., 1997). However, the terminal heights of the observed Aurigids were comparable to those of other meteor showers. With observed value of He 92.55 km, there was no sign of Aurigids p enetrating deep into the atmosphere. The Hb of the Aurigid at 11:04:36 UT , 137.1 km, is significantly higher compared to 120-125 km for the remaining four double station Aurigids. This meteor is the first high altitude Aurigid (Hb > 130 km) recorded (see section 8.5 for details).


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154

8.4.4

Orbital Elements

The orbital elements of the Aurigids are given in Table 8.7. These are p erihelion distance (q), semi ma jor axis (a), inclination (i), longitude of the ascending node (), argument of p erihelion ( ), and mean anomaly (Mo ). These are compared with those of the annual shower Time [UT] 10:53:31 10:55:50 11:04:36 11:30:01 12:02:40 Annual Shower Comet Kiess
31

and the parent comet C/1911 N1 (Kiess)32 . q [AU] 0.714 0.669 0.670 0.638 0.680 0.802 0.684 1/a [AU-1 ] -0.119 -0.045 -0.127 0.128 -0.137 - 0.005 i [deg] 147.698 148.988 149.400 147.884 149.216 146.4 148.421 [deg] 158.526 158.528 158.534 158.551 158.572 158.978 158.978 [deg] 116.805 110.232 111.484 103.876 112.601 121.5 110.378 Mo [deg] 1.422 1.018 1.656 2.869 2.456 - 0.037

Table 8.7: Osculating orbital elements of Aurigids These orbits are highly eccentric, making it difficult to compute the semi-ma jor axis accurately. It is very sensitive to the geocentric velocity, so even a small uncertainty in this quantity results in a large uncertainty in semi-ma jor axis. So these meteors are not hyp erb olic (due to negative 1/a), but has large uncertainty in semi-ma jor axis. All other orbital elements of the Aurigid dust trail are in good agreement with that of their parent comet Kiess. The disp ersion in the inclination of the meteoroids is low, only 2 . The median value of i=148.988 is in very good agreement with the parent comet's 148.421 (compared to that of the annual shower 146.4 ). The values of for all five meteoroids are consistent, increasing with UT as exp ected. The meteoroids seem to b e spread in , with a standard deviation of 4.68 . The median value of = 111.484 is in good agreement with that of parent comet's = 110.378 , whereas of the annual shower is 121.5 , significantly higher than that of the observed outburst. The close resemblance b etween the orbital elements of the comet Kiess and the observed
31 32

Jenniskens, (2006) http://ssd.jpl.nasa.gov/


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155

five double station Aurigids strongly suggests that these meteoroids were indeed ejected from Kiess 2000 years ago. The difference of the orbital elements of the 2007 outburst from the annual shower also demonstrates the existence of a distinct comp onent within the Kiess debris stream.

8.4.5

Photometry

The maximum (ie p eak brightness) visual magnitude MM

ax

(Optical Johnson V band,

500-600 nm) of the double station meteors is shown in column 8 of Table 8.6. The absolute magnitude of a meteor indicates its brightness as it would app ear at a distance of 100 km in the direction of the zenith. For single station meteors, their exact height is not known, so a height at maximum brightness of 103±3 km is assumed as calculated from the double station Aurigids. The error caused by this is 0.12 magnitude, somewhat less than our photometric uncertainties (0.2 mag). The absolute magnitude distribution for the Aurigids and the sp oradics are shown in Fig. 8.10. The meteors observed by the image-intensified camcorders were not included in this plot, as the sp ectral sensitivity of these cameras is different than that of the CCD video cameras (WaTec and Mintron). The sp oradic background was abundant in meteors with magnitude +0.5 to +2.5. In contrast, the Aurigid outburst was abundant in brighter, -2.0 to 1 magnitude meteors. There were 14 Aurigids recorded brighter than a magnitude of -1.0, that of the brightest sp oradic recorded. The brightest Aurigid, recorded at 12:02:40 UT, was of magnitude -3.4. Similar to past Aurigid outbursts, the 2007 outburst was rich in bright meteors. Jenniskens & Vaubaillon (2007b) also rep orted an observed abundance of bright, -2 to +3 magnitude meteors from airb orne observations.


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156

12 Aurigids Sporadics 10 8

Number

6 4 2 0 -4 -3 -2 -1 0 1 2 3 4

Absolute magnitude
Figure 8.10: Absolute magnitude distribution of Aurigids (Red-b old line) and Sp oradics (blue-dashed line).

8.5

Discussion

Our observations of the 2007 Aurigid meteor outburst are consistent with most of the predictions made by JVa. However, the terminal heights of the meteoroids He were not as low as exp ected by JVa. This suggests that the 2007 Aurigid outburst was different in some way to the 1995 -Monocerotids, even though they are b oth caused by ejecta from long-p eriod comets. The Hb of the Aurigid recorded at 11:04:36 UT is significantly higher than those of the other four Aurigids. The Hb of the 11:04:36 UT Aurigid observed by the Mintron camera at Fremont Peak is 131.5 km, and by the image-intensified camcorder at Lick Observatory is 137.1 km. This is b ecause the image-intensified camcorders are more sensitive light detectors, as they recorded on average 3.7 times more meteors p er unit time and sky surface area than the Mintron cameras. The absolute magnitude of the 11:04:36 UT and 10:55:50 UT Aurigids, observed with the same Mintron camera at


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157

-1 -0.5 105550 110436

Absolute Magnitude

0 0.5 1 1.5 2 2.5 3 135 130 125 120 115 110 105 100 95

Height [km]
Figure 8.11: Absolute magnitudes of 110436 and 105550 Aurigid. Fremont Peak, plotted against height are shown in Fig. 8.11. The light curve of the 10:55:50 UT Aurigid is relatively smooth, whereas that of the 11:04:36 UT Aurigid fluctuates. This fluctuation is similar to the high-altitude meteors studied by Koten et al. (2001). The light curve shap e and Hb of the high-altitude meteors could b e explained by taking into account sputtering from the meteoroid surface along with the traditional ablation model (Vinkovi´, 2007). Spurny et al. (2000) distinguished c ´ three distinct phases of high altitude meteor radiation; (i) a diffuse phase with the sputtering dominated region (ab ove 130 km), (ii) the intermediate phase where b oth processes contribute comparably (120 - 130 km) (iii) the "sharp" ablation phase where the radiation is given solely by meteoroid ablation (b elow 120 km). Koten et al. (2006) studied the b eginning heights and light curves of high altitude (>130 km) meteors, using double station data obtained at Ondejov/Kuunak during r z April 1998 - May 2005. In addition, Leonids observed from various locations from 1998 - 2001, including the ma jor outbursts in the year 1999, 2000 and 2001 were included. Only 164 meteors, ab out 5%, had Hb greater than 130 km. This emphasises the rare


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158

occurrence of high-altitude meteors. Also noteworthy is that 148 of those high altitude meteors were Leonids, with only a tiny fraction (16) b eing Perseids, Lyrids, -Aquariids or Sp oradics. Koten et al. (2006) give a relationship b etween maximum brightness Mmax and b eginning heights Hb as:

Hb = -3.5(±0.1) Mmax + 124.4(±0.4)

(8.2)

according to which any meteor brighter than magnitude -1.6 would have a b eginning height of 130 km or higher. There were in total 9 Aurigids observed (out of 35 Aurigids) with maximum magnitude brighter than -1.5, and thus these Aurigids could also have Hb greater than 130 km, resembling the 11:04:36 Aurigid. The 2007 Aurigid outburst is similar to the Leonids in that they b oth have similar Hb , He , Hmax and contain high-altitude meteors. Leonids are among the fastest meteor showers, with V =71 km s
-1

. The parent comet of the Leonids, 55P/Temp el-Tuttle,

has a orbital p eriod of 33.24 years. It is imp ortant to note that the comparison is not b eing made with the annual Leonid shower, but rather with Leonids from 1998-2001, including several outbursts. This p oints to a similarity b etween meteor outbursts due to ejecta from short and long p eriod comets. The b eginning height of cometary meteors increases with increasing mass (Koten et al., 2006). High altitude meteors corresp ond to meteoroids that are loosely cohesive and probably contain volatile elements such as Na which starts to ablate high in the atmosphere. This suggests that the 2007 Aurigids were p erhaps rich in volatile elements, such as Na, which causes bright and high altitude meteors. Such volatile elements could b e still present in the 1-revolution ejecta as the meteoroids ejected from the comet at the p erihelion 2000 years ago have sp ent very little time in the inner solar system.


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159

8.6

Conclusions

The 2007 Aurigid meteor outburst occurred as predicted. The observed ZHR was half of the predicted value. However, the predictions for p eak activity time, radiant and velocity were consistent with the observed values. These Aurigids were bright as exp ected with 26 brighter than 0 magnitude. The close agreement b etween the predicted and the observed parameters of this outburst highlights the advancement in meteoroid ejection models from comets and their evolution through time for up to several millennia. The tra jectory of meteors were compared b etween different cameras to test the SPARVM and Metrec software packages. The compactness of the radiant, velocities and the good agreement of the orbital parameters of the outburst Aurigids with that of the parent ob ject demonstrates the fidelity of SPARVM. The Aurigid recorded at 11:04:36 UT is the first high-altitude Aurigid documented. However, as inferred from the magnitude distribution, there should b e more Aurigids with similar b eginning heights. The Hb , He and Hmax of the 2007 Aurigid outburst are in close resemblance to those of Leonid outbursts. The identification of a high-altitude Aurigid further strengthens the case for similarity b etween outbursts from debris of long and short p eriod comets. The presence of a bright, high altitude meteor also suggests the p ossibility of volatile elements such as Na in these meteoroids.


Chapter 9

Conclusions and Future Work

9.1

Conclusions

A software package, SPARVM, was successfully develop ed, tested and used for the reduction and analysis of video meteor records. It is a complete package for analysing video records with a focus on double station meteors. The accuracy of the results obtained is of publishable standard, and compares quite favourably to other available software packages. The meteor detection module discussed in Section 4.4 is able to compute the meteor centre with sub-pixel accuracy. The median value for
met

was only 0.30 pixels from
met

the 6567 meteors from AOMD from Section 7.3. Ab out 95% of the meteors had

less than 3.0 pixels. Considering the large amount of meteor records reduced, with some of them b eing fireballs and fragmenting meteors, the p ercentage of accurately reduced meteors is quite high. The p osition of the meteor centre transformed into equatorial coordinates is compared with Metrec in Section 8.3. The good match of the two meteor tra jectories shows that the meteor p ositions estimated by two different software packages are in good agreement. The Astrometry module discussed in Section 5.7 is also able to transform p osition

160


9.1 Conclusions

161

from image/video coordinates to standard coordinate systems with a sub-pixel accuracy. Ab out 90% of the meteor records from Cam-1 whose astrometric transformation was computed had
astr o

less than 0.3 pixels. Even though it is typical to have sub-pixel

accuracy for astrometric transformation in professional astronomy, the result here was obtained from off-the-shelf video cameras with inexp ensive CCDs. The photometric transformation resulted in
photo

of 0.2-0.5 magnitudes, with the mean

photo

of only

0.22 magnitudes. The magnitude estimated by SPARVM is also compared with the magnitude computed by Metrec in Section 8.3. Again, there was a reasonable agreement b etween the two magnitude estimates. The double station reduction and orbital element computation modules discussed in Section 6.3 and 6.5 are also able to produce reliable results. This was shown by comparing the computed orbit of an Ursid meteor with that from the IMO database calendar and that of the parent comet 8P/Tuttle. The double station reduction module was compared with two other software packages, UFO-Orbit and KNVWS, in Section 6.4. The result of the comparison showed that SPARVM is as good as, if not b etter than, these two software packages. There is also agreement in the computed parameters of the Geminid shower from the meteor records of AOMD and those of the IMO calendar and parent 3200 Phaethon as seen in Section 7.5. Similarly the comparison of the double station results of Aurigids with the annual shower and the parent comet 1911 C/N1 (Kiess) shows that SPARVM is able to reduce and analyse meteor videos accurately for mobile as well as fixed stations. Chapter 7 describ ed the detailed testing of each individual module of the software on a large data-set of 6567 meteor records. This showed b oth the robustness and flexibility of the software in reducing such a large data-set, as well as exp osing its limitations, where the software produces comparably high uncertainty. Double station meteors consist of observations from Cam-4 (Bangor) and one or more of Cam-1, Cam-2 and Cam-3 (Armagh). The comparison b etween the double station meteors observed by b oth Cam-1 and Cam-3 showed very good agreement. There was a difference of less


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162

than 3 in R.A. and Dec. in 87% and 95% of the meteors from these two cameras, resp ectively. The velocity difference of 80% of the meteors was less than 3 km s the median difference value of only 0.885 km s
-1 -1

with

.

The reliability of the double station catalogue was checked by analysing Geminid meteors and comparing it with catalogue values. The comparison of the orbital elements of Geminid meteoroids with its parent 3200 Phaethon showed good agreement. The orbital elements of six minor showers were with their p ossible parent candidate and found that asteroid 1998 SH2 is a p ossible parent of -Virginid meteor shower. Only orbital similarity is not enough to relate a parent ob ject to a meteor stream, and thus physical characteristics of 1998 SH2 should b e compared with those of the -Virginid meteoroids. A rather inconspicuous outcome of this thesis, alb eit a very imp ortant one, is the level of automation of the software. All 6567 meteor records can b e reduced by using two routines (one in p erl and one in IDL). This is essential b ecause there are hundreds of GB of data from different observers waiting to b e reduced. The drawback of the automation is that not all the meteors are reduced with the same uncertainty. But SPARVM is able to reliably reduce more than 80% of the meteors. This is quite a high p ercentage for a software to achieve on its first release. The software was successfully used for meteor records observed from Northern Ireland and California. Meteors observed by cameras with different optics (focal lengths of 3.8 mm, 6.0 mm and 8.0 mm) and different versions of the capture software (UFO-Capture V1.0 and V2.0) were reduced successfully. Even meteors observed by cameras equipp ed with image intensifiers (Aurigids) were reduced and analysed (except photometrically). This shows the degree of flexibility of the SPARVM package. In addition to the development of the software, the Armagh Observatory Meteor Database (AOMD) was created. The database contains the results of 6567 meteor videos observed from different cameras and locations. SPARVM can b e used to reduce meteor records from January 2008 onwards to increase the numb er of meteors in the


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163

AOMD. Furthermore, a list of publishable standard results obtained from analysing 457 double station meteors were compiled as shown in App endix B. The research that can b e done using these results are shown in the Future Work section. A detailed analysis of the 2007 Aurigids enabled us to confirm that the outbursts occurred at the predicted time of 11:15±5 UT. The comparison of the radiant of observed Aurigids with those of the prediction and annual Aurigid radiants suggests that the 2007 Aurigid outburst was caused due to debris ejected from the parent comet C/1911 N1 (Kiess) around 80 BC. The observed ZHR, however, was half of the predicted value. These Aurigids were bright as exp ected with 26 brighter than 0 magnitude. The b eginning and ending heights of these Aurigids resembled those of Leonid outbursts suggesting a similarity b etween outbursts from debris of long and short p eriod comets. The Aurigid recorded at 11:04:36 UT is the first high-altitude Aurigid documented. The presence of bright and high altitude meteors suggest the p ossibility of volatile elements such as sodium (Na) in these meteoroids.

9.2

Future Work

There are various lines along which the software can b e improved in the future. The detection of stars in a meteor video is very imp ortant and can b e improved further by using advanced techniques of background reduction, or by increasing the threshold of the star detection limit. Other ways to improve astrometry and photometry are to combine information from multiple videos, assuming that the cameras have not moved significantly, and to compute one transformation from all the meteor records. A current limitation of the software is that it requires matching stars manually for the first stage in the astrometric transformations. This can b e improved up on by using algorithms that match the pattern of the stars without providing a priori information. The detection of the meteor centre can also b e improved. The centroiding algorithm develop ed for this thesis could b e used in combination with other centroiding


9.2 Future Work

164

algorithms. Modifications can b e made to analyse only part of the frames which would allow for the detection of multiple meteors in one single video. The double station reduction and orbital element computation requires very little modification in the future. That b eing said, the computation of the station-meteor tra jectory planes from two stations and its intersections can b e improved by using a combination of different methods. Various parameters used in the computation such as p osition and mass of the Earth and Sun should b e up-to-date. The sphere of influence of Earth's gravitational field is computed using only the gravitational force of the Earth and the Sun. But b ecause the gravity of the Moon also affects this sphere, its inclusion when calculating Earth's gravitational sphere can in principle improve the software. The software should b e tested for meteors recorded by different cameras and capture methods. Different formats of videos and images should b e used to test the flexibility of the software. Frames extracted by using a frame grabb er other than Mplayer should also b e tested. A pro ject to build a virtual observatory (VO) for meteoroids is well under way (Koschny et al., 2009). The VO is categorised into different observation techniques such as visual, radio, photographic and video. A different category is set for double station meteors and their orbital elements. The output format of SPARVM should b e modified as sp ecified by the VO, so that single and double station meteor records reduced by the software can b e easily transferred to the Virtual Observatory database. SPARVM analysed 457 double station meteors with their occurrence time, p osition of the radiants, velocities, and orbital elements. This database can b e used for different typ es of research on meteors and the scientific imp ortance of this reduced data is very significant. Addressing all p ossible scientific uses of the AOMD is b eyond the scop e of this work, but Section 7.6 searched for p ossible shower associations with parent ob jects. In future this work could b e extended using the orbits of all the near Earth ob jects. The criteria for meteoroid stream identification such as DN (Jop ek et al., 1999), DS
H

(Southworth & Hawkins, 1963) and DR (Valsecchi et al., 1999) should b e calculated


9.2 Future Work

165

which relates the appropriate distance b etween the two orbits. The showers used were only those included in the "All list of established showers". There are more showers with unknown parent b odies in "The working list of showers" and "The list of all showers". Comparing the orbits of these meteors with those of near Earth ob jects and comets may reveal the parents of these showers. Another line of research would b e to simply identify meteors from new p ossible showers. With the quantity of data available, new showers can b e identified. The database contains many sp oradic meteors and a detailed study of their distribution and a comparison with results from radar meteors would b e a interesting topic to pursue.

Figure 9.1: Northern Taurids, Southern Taurids and Orionids. The investigation of ma jor showers is a p opular research area due to the availability of a large numb er of meteors. Fig 9.1 shows two ma jor shower groups, the Taurids (blue) at RA = 50 and the Orionids (Orange) at R.A. = 150 . The Taurids are


9.2 Future Work

166

clustered in two separate groups on either side of Dec. = 20 , the top one b eing the Northern Taurids and the b ottom one b eing the Southern Taurids. The meteors from these two groups can b e used to detect changes from year to year as p ostulated by Asher & Izumi (1998). Similarly, Orionids are one of the faster meteor showers with V = 66 km s
-1

. The light curves and b eginning/terminal heights of Orionids can b e

compared with those of slower meteors such as the Taurids.


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Appendices

173


App endix A

Watec CCD and Computar Optics Specifications

Figure A.1: Technical sp ecifications of Watec (902DM2s) CCD used at Armagh Observatory. 174


175

Figure A.2: Technical sp ecifications of Computar 6 mm focal length optical system used in Cam-1.


176

Figure A.3: Technical sp ecifications of Computar 3.8 mm focal length optical system used in Cam-2 and Cam-3.


App endix B

AOMD Database
The software package used for the analysis of video meteors is online at http://star.arm.ac.uk/atr/sparvm/ It contains SPARVM routines develop ed by the author, astrolib routines used in SPARVM, p erl routine to extract the frames from videos, documentaion ab out SPICE intsllations, and documentation ab out SPARVM software package. The double station meteors from Cam-1 and Cam-3 are compiled into a catalogue of meteors . This lists only containes meteors Observed b etween Cam-1/Cam-4 and Cam-3/Cam-4 from 2005/06/25 until 2007/12/31. The meteors observed by b oth Cam-1 and Cam-3 are denoted by " * " in the ID. The result for those meteors are the mean values computed from the two pairs. The reliability of the results can b e assesd from the difference in velocity b etween two stations (V1 and V2 ). For example, meteor (ID = 0001) has velcoity difference of 18.19 km s
-1

, and thus the results are less reliable. It can also b e seen that the semi-

ma jor axis (a) is -1.89 AU for this meteor. The meteor (ID = 0002) has a velocity difference of only 0.24 km s
-1

, and the result for this meteor is highly reliable.

177


178

ID Date Time R.A. Dec. V1 V2 q
o

= = = = = = = = = = = = = =

Reference ID for the meteor (4 digit unique code) Date of meteor occurrence (yyyy/mm/dd) Time of meteor occurrence at Armagh Observatory (hr:min:sec) Right Ascension of the radiant of the meteor (deg) Declination of the radiant of the meteor (deg) V calculated from Station-1, Armagh Observatory (km s-1 ) V calculated from Station-2, Bangor (km s-1 ) Perihelion distance (AU) Semi-ma jor axis Eccentricity Inclination (deg) Longitude of the ascending node (deg) Argument of p erihelion (deg) Mean anamoly

a e i M0


ID

Date Y/M/D

Time H:M:S 23:30:19 00:19:03 01:03:15 01:05:23 01:13:08 22:27:44 22:34:34 23:13:15 01:42:18 23:20:30 00:09:07 00:11:49 00:30:23 00:35:30 01:02:09 22:57:21 23:22:09 23:27:48 23:32:15

R.A. deg 240.15 280.80 311.75 131.03 11.82 27.38 33.35 44.21 339.80 41.22 299.82 42.45 35.90 38.88 39.46 43.03 38.15 38.79 315.71

Dec. deg -27.85 -20.49 38.57 50.29 27.21 53.92 54.74 55.07 -2.30 55.83 6.92 55.50 58.14 44.89 56.21 56.69 61.06 57.68 33.78

V1 km s
-1

V2 km s
-1

qo AU 0.8359 0.4635 0.8433 0.8582 0.8549 0.9383 0.9269 0.3875 0.0600 0.9029 0.7557 0.9119 0.9504 0.1909 0.8815 0.9224 0.9566 0.9476 0.6794

a AU -1.89 2.34 4.20 2.65 2.91 11.94 7.32 0.83 2.33 3.51 3.77 5.46 4.00 0.62 2.29 14.44 -0.95 -5.92 1.15

e

i deg

deg 273.46 274.53 94.46 96.35 99.24 124.89 128.72 127.79 130.75 133.54 134.52 134.53 134.54 134.54 134.56 135.44 134.50 134.50 134.50

deg 44.73 101.77 229.67 130.46 130.49 150.61 147.47 38.37 334.81 140.49 243.25 143.61 152.28 6.52 127.62 147.10 158.90 154.43 275.95

M0 deg 160.70 347.83 356.25 7.99 6.77 0.50 1.16 93.24 351.18 4.36 354.91 2.30 2.54 156.90 22.55 0.41 12.37 1.29

0001 0002 0003 0004 0005 0006 0007 0008 0009 0010 0011 0012 0013 0014 0015* 0016 0017 0018 0019

2005/06/25 2005/06/26 2005/06/26 2005/06/28 2005/07/01 2005/07/27 2005/07/31 2005/07/31 2005/08/03 2005/08/06 2005/08/07 2005/08/07 2005/08/07 2005/08/07 2005/08/07 2005/08/07 2005/08/07 2005/08/07 2005/08/07

15.45 25.66 44.78 14.72 63.04 58.23 58.41 33.66 40.73 55.77 19.88 56.92 55.42 27.06 50.24 58.89 73.43 62.32 19.06

33.64 25.42 44.10 14.99 62.99 58.64 57.84 42.93 40.62 57.25 20.14 59.23 55.86 40.03 56.88 59.22 62.19 59.73 17.45

1.4414 0.8018 0.7992 0.6764 0.7060 0.9214 0.8733 0.5324 0.9743 0.7429 0.7995 0.8330 0.7624 0.6908 0.6147 0.9361 2.0052 1.1601 0.4101

7.11 1.08 78.58 8.87 143.00 112.17 112.76 87.68 19.39 112.28 13.61 114.09 108.09 86.80 108.78 113.60 111.70 112.74 27.24

179

311.35


0020* 0021* 0022* 0023 0024* 0025* 0026* 0027 0028* 0029 0030 0031 0032 0033 0034 0035* 0036 0037 0038 0039* 0040

2005/08/14 2005/08/14 2005/08/14 2005/08/14 2005/08/14 2005/08/15 2005/08/15 2005/08/16 2005/08/16 2005/08/17 2005/08/19 2005/08/20 2005/08/20 2005/08/23 2005/08/23 2005/08/24 2005/09/02 2005/09/02 2005/09/02 2005/09/02 2005/09/02

00:19:50 00:37:29 00:38:12 00:44:05 21:41:20 00:11:44 00:29:53 22:45:29 23:46:28 01:52:35 00:41:10 23:55:08 23:57:54 00:37:24 01:24:19 21:59:26 00:05:33 00:25:26 02:07:06 02:08:09 02:32:23

344.42 49.14 51.80 49.74 49.94 55.65 56.82 50.95 151.82 51.03 21.72 34.17 277.43 30.75 305.30 327.02 92.16 11.66 31.44 272.62 88.63

1.46 58.05 61.45 58.69 60.71 64.02 57.41 62.09 10.77 54.46 26.53 73.95 57.65 33.52 42.82 -13.29 39.79 79.06 -1.39 62.58 9.13

36.77 58.52 55.87 55.94 58.26 55.69 55.00 57.18 56.59 61.07 64.40 47.01 19.92 53.63 26.32 19.19 67.04 44.49 51.07 20.30 65.18

34.27 59.53 56.28 55.79 58.06 54.86 56.06 58.46 71.69 61.23 63.55 46.54 22.60 62.78 26.66 19.26 66.58 43.31 48.01 20.34 65.41

0.1373 0.9351 0.9089 0.9177 0.9362 0.8935 0.8363 0.9461 0.9703 0.9564 0.5659 0.9834 0.9933 0.5960 0.8823 0.6798 0.6790 0.9993 0.1139 0.9997 0.7132

1.87 12.93 6.19 3.30 19.36 9.23 2.94 28.50 -0.29 11.78 26.32 3.43 3.10 1.91 10.25 2.51 -14.96 5.70 1.63 2.61 5.73

0.9265 0.9277 0.8532 0.7219 0.9516 0.9032 0.7160 0.9668 4.3442 0.9188 0.9785 0.7134 0.6793 0.6880 0.9139 0.7289 1.0454 0.8246 0.9301 0.6165 0.8755

14.59 113.49 107.12 110.48 110.06 103.53 112.12 108.46 80.92 120.36 145.97 85.50 33.28 138.74 36.43 3.54 148.27 76.62 119.27 32.42 150.90

141.24 141.26 141.26 141.27 142.10 142.20 142.22 144.07 143.14 144.19 146.07 147.00 147.00 149.92 149.94 331.77 159.56 159.57 339.63 159.63 339.65

322.56 149.89 143.28 143.50 150.40 140.69 126.80 152.89 195.09 155.37 263.00 163.79 190.44 272.97 221.10 76.05 111.84 183.23 147.15 182.06 292.68

346.09 0.68 1.82 4.36 0.26 2.18 11.40 0.28 114.66 0.43 359.59 1.96 358.58 332.22 359.19 349.31 0.63 359.84 342.43 359.74

180

2.77


0041 0042 0043* 0044 0045 0046 0047 0048 0049 0050 0051 0052 0053 0054 0055 0056 0057 0058 0059 0060 0061

2005/09/02 2005/09/02 2005/09/03 2005/09/03 2005/09/16 2005/09/19 2005/09/19 2005/09/20 2005/09/28 2005/09/28 2005/10/13 2005/10/13 2005/10/14 2005/10/14 2005/10/14 2005/10/14 2005/10/14 2005/10/16 2005/10/22 2005/10/23 2005/10/23

03:17:18 23:51:59 00:29:08 22:41:42 22:48:05 04:21:21 23:35:02 00:23:19 00:33:05 03:42:40 23:53:29 23:59:27 00:25:00 00:48:51 02:03:56 02:21:33 02:58:56 03:48:51 05:22:25 03:58:53 04:27:29

75.67 50.66 71.08 55.19 340.87 98.58 114.06 59.43 319.47 174.52 32.69 101.74 42.16 99.63 106.79 38.30 86.51 287.54 96.06 96.48 96.87

58.18 44.52 52.91 35.18 67.67 59.15 58.65 20.90 46.87 57.17 18.22 20.47 15.24 31.94 53.88 5.12 39.26 70.45 15.47 15.87 15.86

58.53 71.46 61.24 65.41 29.61 34.55 51.96 58.61 17.03 28.85 31.44 66.81 31.99 71.91 74.24 29.40 64.31 30.21 64.75 63.98 65.97

57.27 65.00 62.64 65.07 29.03 55.69 54.72 55.92 14.54 46.65 31.25 67.31 33.44 66.18 60.51 29.45 60.37 23.23 63.29 65.64 66.23

0.9310 0.9483 0.9731 0.8935 0.8772 0.6259 0.7804 0.3185 0.9330 0.6546 0.2581 0.9131 0.1653 0.8614 0.9572 0.3114 0.5667 0.9935 0.5466 0.5507 0.5837

3.18 -4.83 4.51 3.02 1.68 1.36 1.95 1.36 2.10 3.13 2.11 2.63 1.54 11.32 -2.85 1.89 3.51 5.52 3.41 4.58 8.31

0.7070 1.1963 0.7842 0.7040 0.4786 0.5409 0.6008 0.7653 0.5564 0.7911 0.8775 0.6528 0.8930 0.9239 1.3353 0.8349 0.8384 0.8199 0.8397 0.8797 0.9298

116.70 137.61 127.25 152.98 51.49 99.20 109.05 179.87 22.05 61.55 5.55 174.69 4.08 164.40 127.54 14.40 146.10 41.55 162.42 163.41 163.84

159.68 159.55 160.54 161.44 174.07 176.25 176.06 355.97 184.90 185.04 199.65 19.65 20.71 200.70 200.75 20.77 200.79 202.80 28.82 29.76 29.78

146.41 205.54 159.84 222.08 231.65 79.42 114.15 124.02 215.69 96.84 305.99 38.72 140.27 225.48 203.66 120.89 267.65 189.79 89.68 87.78 82.18

4.41 177.23 1.69 354.41 342.64 78.86 16.48 330.57 351.29 23.79 347.16 353.45 340.45 175.50 173.34 343.92 352.07 179.15 353.10 355.55

181

358.36


0062 0063 0064 0065 0066 0067 0068 0069 0070 0071 0072 0073 0074* 0075 0076 0077 0078* 0079 0080 0081 0082

2005/10/26 2005/10/26 2005/10/28 2005/10/28 2005/10/29 2005/10/29 2005/10/29 2005/10/29 2005/11/11 2005/11/12 2005/11/12 2005/11/14 2005/11/17 2005/11/17 2005/11/17 2005/11/17 2005/11/17 2005/11/19 2005/11/19 2005/11/19 2005/11/19

00:27:16 00:42:11 20:05:11 23:51:49 00:00:38 01:46:01 02:52:07 04:05:01 19:44:24 05:51:02 23:46:56 01:02:18 03:10:46 03:59:30 04:34:42 05:36:43 22:33:23 01:48:37 02:25:12 03:19:25 04:29:01

96.48 51.77 48.23 42.38 143.36 48.04 98.50 132.57 56.46 59.99 58.55 59.16 152.82 153.14 269.72 131.70 261.63 153.54 62.80 146.46 154.19

16.90 76.32 15.63 19.37 32.80 20.81 39.19 46.53 17.02 25.31 16.48 17.10 23.45 22.16 51.14 53.51 59.02 23.68 17.92 48.93 22.26

66.10 40.02 30.75 30.37 48.29 29.04 60.76 64.47 13.61 26.15 25.75 25.41 66.03 65.01 16.01 56.10 23.18 71.15 21.12 36.07 68.92

59.77 39.41 30.52 28.71 69.66 28.94 59.41 63.47 24.81 26.54 26.64 21.29 71.78 67.30 16.27 53.59 23.90 62.85 18.00 46.48 67.27

0.4451 0.7953 0.2855 0.3513 0.6216 0.3043 0.4238 0.9888 0.4946 0.3869 0.4137 0.4586 0.9925 0.9914 0.9789 0.6715 0.9809 0.9996 0.5399 0.4193 0.9982

3.93 3.89 2.13 2.67 2.90 1.86 3.01 4.87 1.23 1.85 2.01 1.66 5.01 2.09 2.31 2.82 2.64 2.68 1.45 0.82 3.19

0.8867 0.7957 0.8660 0.8684 0.7860 0.8365 0.8594 0.7970 0.5994 0.7908 0.7945 0.7245 0.8017 0.5267 0.5757 0.7621 0.6290 0.6275 0.6283 0.4861 0.6870

164.19 66.30 6.24 2.18 144.28 2.39 141.71 131.86 5.75 3.28 5.49 4.49 160.05 161.49 23.51 109.13 37.45 158.98 3.88 96.89 161.13

32.60 212.62 35.45 214.52 215.59 215.61 215.70 215.75 49.47 229.83 50.64 51.70 234.79 234.82 234.83 234.89 235.60 236.75 56.80 236.81 236.86

101.59 237.46 122.63 293.38 84.92 301.88 284.33 192.91 112.02 292.90 108.90 106.84 165.39 167.10 160.46 256.28 161.95 177.12 101.12 324.01 174.62

350.81 355.37 347.12 350.62 62.86 343.65 351.87 359.10 319.37 342.55 344.66 338.13 8.64 3.71 4.55 350.62 3.35 1.22 331.23 254.61

182

0.79


0083 0084 0085 0086 0087 0088 0089* 0090 0091* 0092 0093* 0094 0095 0096* 0097 0098 0099 0100* 0101 0102 0103*

2005/11/19 2005/11/19 2005/11/20 2005/11/20 2005/11/20 2005/11/20 2005/11/20 2005/11/20 2005/11/20 2005/11/20 2005/11/20 2005/11/20 2005/11/21 2005/11/21 2005/11/21 2005/11/21 2005/11/21 2005/11/21 2005/11/26 2005/11/28 2005/12/01

04:34:58 21:00:21 00:49:04 03:00:12 03:13:04 03:37:25 04:16:05 04:58:00 05:05:53 05:15:51 21:48:49 23:29:28 00:54:29 01:21:35 04:18:05 04:37:45 05:08:11 20:09:47 23:10:16 00:08:55 22:23:21

65.33 46.60 146.63 145.55 125.70 154.94 136.72 125.42 68.07 64.53 53.21 137.27 21.25 67.09 69.32 155.89 155.83 275.49 88.75 95.84 165.64

24.16 21.21 25.51 44.82 32.26 21.73 36.07 -7.16 29.14 19.62 1.71 22.07 49.27 25.89 13.64 20.55 21.44 45.93 15.78 1.31 44.97

25.43 20.64 60.03 61.80 43.00 67.03 60.51 62.67 26.77 22.27 19.21 74.48 14.85 26.10 27.07 68.22 67.91 17.79 40.98 43.54 62.58

23.92 20.51 59.42 57.45 60.29 64.94 60.97 64.32 27.25 23.13 19.54 67.27 13.32 26.95 20.76 68.47 66.69 19.23 41.19 42.70 62.45

0.4332 0.6608 0.8246 0.8255 0.2444 0.9978 0.6364 0.8027 0.3820 0.5010 0.7095 0.8085 0.8851 0.3952 0.4616 0.9979 0.9989 0.9684 0.1170 0.2143 0.9369

1.79 2.87 1.09 2.61 1.65 2.02 2.05 8.21 1.93 1.80 2.37 -14.21 2.11 1.94 1.70 3.23 2.58 2.83 4.30 3.54 215.38

0.7582 0.7701 0.2442 0.6836 0.8520 0.5068 0.6895 0.9022 0.8024 0.7224 0.7008 1.0569 0.5814 0.7962 0.7278 0.6913 0.6134 0.6583 0.9728 0.9394 0.9956

0.99 0.54 157.72 124.75 139.53 161.13 141.39 130.57 6.53 3.34 12.51 170.47 14.04 3.20 9.50 162.97 161.34 26.52 24.76 60.46 119.12

236.73 237.26 237.72 237.80 237.81 237.84 237.86 57.88 237.87 57.94 58.61 238.68 238.71 238.70 58.88 238.89 238.91 239.53 64.72 65.77 249.75

288.46 257.55 263.97 236.01 315.90 173.42 264.91 54.33 292.94 100.90 72.83 232.27 226.57 291.43 106.31 174.16 175.67 156.99 142.24 128.47 209.13

341.11 351.44 303.12 349.51 316.30 2.02 341.04 358.36 343.66 340.87 348.44 174.17 349.31 343.80 338.68 0.80 0.88 3.92 356.37 354.54

183

269.98


0104 0105 0106* 0107 0108* 0109 0110 0111 0112* 0113* 0114 0115 0116 0117 0118 0119 0120* 0121 0122 0123 0124*

2005/12/04 2005/12/05 2005/12/06 2005/12/11 2005/12/11 2005/12/11 2005/12/12 2005/12/12 2005/12/12 2005/12/12 2005/12/12 2005/12/12 2005/12/12 2005/12/12 2005/12/12 2005/12/12 2005/12/13 2005/12/13 2005/12/13 2005/12/13 2005/12/18

00:22:24 05:01:45 22:31:20 21:20:38 21:26:16 21:33:23 00:23:34 00:28:07 01:46:31 02:09:38 02:50:23 03:02:57 04:08:15 05:44:13 06:20:22 06:23:00 00:03:50 00:29:19 03:15:12 06:13:28 19:13:18

104.36 162.25 98.39 109.00 213.48 109.08 110.24 110.80 128.07 153.48 200.50 110.77 113.53 114.03 211.08 173.27 109.77 111.33 127.77 114.41 98.43

35.66 22.54 9.28 33.69 26.84 35.30 34.62 33.78 2.41 34.33 68.57 33.21 35.05 34.25 65.27 -11.13 15.13 33.55 2.29 34.04 17.65

30.93 66.26 41.37 32.49 23.30 33.86 33.90 27.07 57.19 59.86 37.07 28.19 32.24 33.33 27.65 45.56 35.72 34.00 56.10 32.39 31.78

24.63 65.46 41.59 32.30 53.68 32.34 30.85 32.15 57.34 60.74 39.05 31.87 31.75 35.13 31.41 19.32 38.34 32.22 58.97 30.89 30.55

0.1824 0.9261 0.1651 0.1588 0.5608 0.1653 0.1670 0.1807 0.2297 0.5316 0.9611 0.1812 0.1595 0.1363 0.9818 0.1543 0.1040 0.1558 0.2219 0.1610 0.3254

0.94 2.39 5.50 1.23 -0.27 1.31 1.23 1.06 5.87 3.53 2.85 1.11 1.15 1.26 1.32 0.59 1.50 1.28 13.78 1.15 2.65

0.8052 0.6122 0.9700 0.8713 3.0992 0.8734 0.8647 0.8295 0.9608 0.8495 0.6622 0.8365 0.8607 0.8921 0.2552 0.7406 0.9306 0.8782 0.9839 0.8596 0.8772

20.24 154.86 38.31 20.85 19.96 24.52 23.54 19.32 126.92 131.64 65.61 18.37 25.34 27.19 54.88 83.46 22.87 22.82 124.53 22.26 10.00

251.86 253.08 74.83 259.86 259.86 259.87 259.98 259.99 80.05 260.07 260.09 260.09 260.14 260.21 260.24 80.24 81.00 261.01 81.13 261.25 86.91

326.58 216.38 134.07 323.77 243.79 322.22 322.80 323.89 124.90 271.60 205.58 322.96 324.80 326.30 205.26 187.01 149.30 323.67 124.82 324.61 116.37

311.88 352.70 357.37 331.53 198.31 333.99 331.31 321.84 357.44 352.23 355.96 324.71 327.50 333.45 344.95 151.72 341.38 333.37 178.37 327.55

184

350.52


0125 0126 0127 0128* 0129 0130 0131 0132 0133 0134* 0135 0136 0137* 0138 0139 0140 0141 0142 0143 0144 0145

2005/12/18 2005/12/21 2005/12/28 2006/01/03 2006/01/03 2006/01/03 2006/01/03 2006/01/03 2006/01/04 2006/01/04 2006/01/04 2006/01/04 2006/01/09 2006/01/09 2006/01/11 2006/01/12 2006/01/14 2006/01/17 2006/01/20 2006/01/20 2006/01/21

21:59:18 19:35:42 01:33:36 19:18:42 20:36:54 21:11:46 21:31:30 22:42:40 02:47:37 03:41:44 04:30:35 05:15:28 02:36:09 05:47:57 06:51:21 06:21:00 05:28:43 05:44:09 06:07:08 06:47:32 00:17:03

301.98 79.13 310.11 230.20 188.95 230.49 226.61 227.73 192.21 231.84 241.41 228.01 177.99 231.80 219.63 237.74 223.43 167.87 311.57 288.78 154.81

71.06 28.70 69.39 47.88 51.14 50.79 51.49 48.22 52.28 50.49 48.84 51.79 8.84 16.85 69.36 49.84 34.13 33.30 73.39 18.28 4.73

23.89 17.51 15.30 41.17 53.85 40.68 40.14 35.64 48.78 37.89 37.62 36.92 63.20 59.05 32.31 31.32 54.73 41.01 13.13 24.43 40.03

21.56 17.06 16.59 40.84 50.58 34.82 40.10 39.37 46.12 39.02 38.83 36.96 65.81 58.40 31.55 29.52 53.64 41.19 13.11 28.70 40.95

0.9970 0.6999 0.9999 0.9865 0.8253 0.9917 0.9991 0.9863 0.8389 0.9921 0.9683 0.9993 0.5208 0.7272 0.9525 0.9896 0.9972 0.2125 1.0000 0.6625 0.0378

5.20 1.90 2.37 2.21 -19.46 1.89 2.26 1.52 4.74 2.33 3.45 1.86 3.53 9.73 3.69 1.31 5.52 1.49 2.00 3.13 1.35

0.8082 0.6319 0.5785 0.5539 1.0424 0.4741 0.5585 0.3531 0.8230 0.5744 0.7197 0.4629 0.8523 0.9253 0.7420 0.2421 0.8195 0.8576 0.5001 0.7880 0.9720

33.79 1.13 24.13 73.73 89.06 68.17 71.71 69.90 82.90 67.92 64.83 66.67 164.41 112.48 51.54 56.82 98.95 67.75 19.71 29.79 31.51

267.00 269.82 276.32 283.20 283.25 283.28 283.29 283.34 283.51 283.55 283.58 283.62 288.61 288.74 290.82 291.81 293.82 296.88 299.93 299.97 120.73

186.57 257.13 180.01 164.22 229.03 166.39 175.92 160.86 230.11 168.14 157.55 176.12 273.28 115.62 207.32 161.05 173.61 314.90 180.66 103.37 162.19

359.61 342.78 0.19 3.98 178.62 5.32 1.04 9.45 356.52 2.79 2.67 1.38 350.84 1.23 357.23 11.67 0.39 338.11 0.10 8.15

185

339.38


0146 0147 0148 0149 0150 0151 0152 0153* 0154 0155 0156 0157 0158 0159 0160* 0161 0162 0163 0164 0165 0166

2006/01/22 2006/02/17 2006/02/18 2006/02/18 2006/02/22 2006/02/22 2006/02/27 2006/03/05 2006/03/20 2006/03/20 2006/03/29 2006/03/31 2006/04/02 2006/04/03 2006/04/03 2006/04/04 2006/04/07 2006/04/07 2006/04/09 2006/04/09 2006/04/12

01:04:24 00:02:55 06:21:37 19:57:37 00:28:23 02:13:27 01:05:34 23:58:47 02:21:16 02:52:40 03:01:43 23:38:20 01:10:37 02:31:08 02:49:14 02:29:30 02:48:37 23:37:57 01:04:44 01:22:59 01:53:30

225.79 228.29 272.81 283.56 148.69 174.53 159.40 195.67 289.99 221.07 204.20 187.65 181.45 208.96 192.36 278.86 305.17 190.63 32.68 275.23 249.25

67.57 45.46 75.24 66.11 0.87 23.63 -0.24 82.69 53.92 32.96 -14.34 44.24 1.55 -8.23 59.70 39.08 7.51 10.91 44.68 19.91 70.02

29.02 43.82 19.24 22.17 23.22 32.25 26.04 14.71 31.13 36.36 35.07 17.17 16.84 32.18 14.55 41.17 61.36 19.02 13.53 46.57 20.75

29.06 44.31 19.09 23.69 20.95 31.18 27.21 14.26 29.70 35.89 34.47 17.58 16.53 29.60 16.38 42.88 61.07 19.24 15.18 39.35 20.73

0.9664 0.9091 0.9994 0.9930 0.6190 0.3904 0.5029 0.9959 0.9560 0.6280 0.2025 0.8931 0.7445 0.2618 0.9666 0.9994 0.6919 0.7215 0.8489 0.7578 0.9991

2.49 9.85 2.64 2.40 2.30 2.98 2.93 2.13 2.89 3.38 2.19 3.04 1.98 1.77 2.93 2.84 5.81 2.52 2.49 1.04 2.84

0.6122 0.9077 0.6216 0.5858 0.7309 0.8690 0.8283 0.5328 0.6693 0.8140 0.9077 0.7062 0.6240 0.8518 0.6698 0.6481 0.8809 0.7137 0.6585 0.2689 0.6477

48.11 73.41 29.74 37.38 9.95 23.22 9.63 21.69 50.47 53.67 11.05 18.40 1.71 1.96 19.53 75.21 128.69 6.46 7.92 92.24 32.59

301.77 328.09 329.36 329.93 153.16 333.22 158.22 345.18 359.25 359.27 188.21 10.03 192.14 13.05 13.12 14.10 17.07 16.92 18.94 18.98 21.94

204.29 216.00 183.30 168.82 84.43 288.14 95.58 188.75 152.88 260.16 132.53 222.13 70.35 307.30 203.55 176.95 110.01 250.67 128.25 281.34 183.88

355.37 359.22 359.53 2.54 347.22 351.99 351.49 357.98 4.24 353.31 348.55 354.56 344.48 342.74 356.56 0.57 2.76 349.68 9.28 282.16

186

359.47


0167 0168 0169 0170 0171 0172* 0173 0174 0175 0176 0177 0178* 0179 0180 0181* 0182 0183 0184 0185 0186 0187

2006/04/13 2006/04/14 2006/04/14 2006/04/27 2006/04/28 2006/04/28 2006/05/03 2006/05/05 2006/05/10 2006/05/11 2006/05/21 2006/05/23 2006/05/31 2006/06/03 2006/06/03 2006/06/27 2006/06/28 2006/07/02 2006/07/02 2006/07/12 2006/07/13

20:35:52 02:28:50 02:48:45 03:48:04 03:27:24 03:42:56 02:09:40 22:01:41 02:36:19 01:46:12 01:36:21 02:16:59 01:52:11 01:09:01 02:29:12 22:58:46 01:21:04 00:15:42 02:08:05 22:53:00 00:31:42

321.62 226.76 253.90 296.09 260.15 302.71 239.38 234.02 290.70 302.54 229.10 289.82 297.18 332.57 250.57 292.18 279.82 323.27 259.31 32.84 269.62

49.10 -7.32 4.74 43.11 36.33 67.16 -15.48 -8.91 43.36 17.39 54.15 21.59 36.10 11.38 -5.65 54.90 60.34 44.95 56.20 52.08 52.72

38.13 32.34 54.38 45.18 38.96 24.58 34.29 27.90 43.27 58.36 13.92 49.70 48.02 62.40 22.14 24.73 22.10 45.31 23.83 53.59 20.86

38.73 30.91 54.67 43.45 39.04 25.10 35.61 29.25 43.05 58.35 14.30 50.97 45.03 60.54 22.35 24.98 19.33 45.75 24.01 49.68 20.60

0.8105 0.1998 0.3683 0.9939 0.8421 0.9681 0.2098 0.3798 0.9897 0.9481 0.9862 0.7018 0.9024 0.9872 0.6277 0.9662 0.9932 0.9305 0.9918 0.6227 0.9807

11.35 1.40 9.37 7.13 10.09 2.41 2.65 2.23 7.77 3.93 2.11 7.75 10.67 1.82 2.77 1.54 1.67 3.35 10.34 2.58 2.75

0.9286 0.8569 0.9607 0.8606 0.9165 0.5991 0.9209 0.8297 0.8726 0.7590 0.5322 0.9094 0.9154 0.4569 0.7735 0.3708 0.4069 0.7224 0.9041 0.7582 0.6430

60.77 13.81 104.93 76.74 62.13 40.98 5.57 9.00 74.07 116.21 20.53 90.44 80.64 142.33 8.79 44.64 36.11 82.93 35.09 103.02 32.41

23.69 23.92 23.94 36.67 37.63 37.64 42.41 45.17 49.23 50.16 59.78 61.74 69.41 72.26 72.30 96.05 96.14 99.92 99.99 110.35 110.41

127.32 317.24 286.82 170.66 227.95 156.19 310.43 291.60 192.08 208.39 196.21 248.09 217.39 196.58 261.61 208.96 192.48 213.46 190.63 96.71 198.04

0.87 335.87 358.66 0.41 359.07 5.01 351.49 347.25 359.61 357.40 356.01 358.11 178.76 354.31 350.77 347.59 355.33 356.11 359.78 11.91

187

357.07


0188 0189 0190* 0191 0192 0193* 0194 0195 0196 0197 0198 0199 0200* 0201 0202 0203 0204 0205 0206* 0207 0208

2006/07/13 2006/07/14 2006/07/14 2006/07/15 2006/07/15 2006/07/15 2006/07/15 2006/07/17 2006/07/17 2006/07/17 2006/07/18 2006/07/23 2006/07/23 2006/07/24 2006/07/25 2006/07/26 2006/07/30 2006/07/30 2006/07/30 2006/07/30 2006/07/30

23:52:56 00:20:44 22:56:19 00:01:20 01:11:30 01:24:42 02:14:26 23:00:51 23:23:01 23:51:31 01:05:57 22:21:29 22:52:12 00:23:27 01:10:35 23:16:49 00:59:21 01:39:49 01:52:52 01:55:50 02:11:22

316.49 2.60 209.47 355.07 13.43 3.40 38.46 260.47 37.45 33.87 284.24 18.84 333.56 50.24 49.78 314.75 305.86 31.98 27.74 306.64 340.15

-2.24 28.11 74.78 32.26 26.12 51.27 29.99 12.20 40.02 51.32 -15.62 53.76 -16.93 20.31 44.74 -4.77 -6.26 50.68 55.41 -5.98 -14.84

39.05 62.64 20.30 62.68 41.76 53.78 41.40 13.62 63.91 52.62 15.74 56.03 41.01 63.88 49.88 28.52 20.88 57.39 55.17 21.62 40.40

39.24 63.59 20.23 44.31 56.98 55.01 62.70 14.04 60.52 53.30 16.08 56.44 41.19 71.49 56.37 28.79 20.91 58.10 55.59 21.49 40.77

0.1212 0.9603 0.9511 0.6932 0.5921 0.9850 0.3330 0.9243 0.6594 0.6680 0.7720 0.9560 0.0729 0.6162 0.4511 0.3492 0.6090 0.9180 0.9391 0.6001 0.0740

2.25 3.53 2.65 2.23 0.95 4.66 2.29 3.30 14.78 2.42 2.23 5.44 2.68 -12.65 1.68 2.10 2.21 3.32 3.73 2.36 2.45

0.9461 0.7281 0.6415 0.6886 0.3800 0.7884 0.8548 0.7200 0.9554 0.7242 0.6542 0.8241 0.9728 1.0487 0.7312 0.8334 0.7250 0.7236 0.7486 0.7455 0.9698

36.25 136.98 30.46 117.56 136.72 103.67 139.60 10.54 132.58 107.50 0.31 108.21 28.23 177.52 120.02 11.52 6.14 116.86 108.12 6.63 27.31

110.39 111.36 112.25 112.30 112.35 112.36 112.39 114.15 114.19 114.20 295.58 120.83 300.85 120.95 121.89 122.76 126.65 126.69 126.70 126.69 306.71

323.88 205.09 151.05 269.93 83.64 165.00 54.75 215.02 107.33 102.08 64.55 154.51 151.67 103.05 71.33 295.59 266.02 143.57 148.85 266.36 151.74

349.90 357.19 5.14 303.83 94.78 1.19 47.58 355.95 2.45 11.64 347.86 1.46 352.78 7.64 25.67 346.16 346.47 4.34 3.67 347.84

188

351.68


0209 0210 0211* 0212 0213 0214* 0215 0216 0217* 0218 0219 0220 0221* 0222* 0223* 0224 0225 0226 0227 0228 0229*

2006/08/01 2006/08/06 2006/08/06 2006/08/08 2006/08/11 2006/08/12 2006/08/12 2006/08/12 2006/08/13 2006/08/24 2006/08/24 2006/08/24 2006/08/27 2006/08/28 2006/08/28 2006/08/28 2006/08/28 2006/08/28 2006/08/29 2006/08/29 2006/08/29

23:36:19 00:43:56 01:45:17 23:47:23 22:57:18 02:46:15 22:42:14 22:54:05 02:11:13 02:09:21 02:54:55 03:15:16 22:37:59 02:19:30 21:55:54 22:16:28 22:27:57 23:49:29 01:48:49 02:01:35 21:28:29

39.74 36.03 16.83 247.12 44.21 40.48 48.78 51.78 136.13 41.58 4.12 37.33 67.45 0.83 348.00 56.19 205.91 356.30 334.10 86.67 53.88

55.86 59.44 54.70 56.42 56.07 58.70 59.04 59.85 77.45 6.62 67.61 37.99 59.03 34.30 -4.36 26.40 65.08 7.68 24.20 51.62 59.30

56.80 56.62 51.85 22.78 61.93 51.38 57.36 54.88 29.80 67.57 43.35 52.55 55.06 50.50 28.16 69.42 25.92 34.58 31.62 22.96 58.42

55.13 55.33 54.41 31.07 55.10 60.70 57.31 55.91 39.30 67.14 45.05 64.13 58.81 47.37 28.61 71.42 25.76 34.51 31.95 49.79 59.05

0.8536 0.9400 0.9971 0.9986 0.9428 0.9471 0.9192 0.8862 0.7905 0.7067 0.9668 0.7224 0.9236 0.3684 0.3469 0.9735 0.8977 0.1455 0.5383 0.3170 0.9995

3.98 6.61 2.59 -3.06 5.98 5.16 6.07 3.62 3.52 31.83 3.04 1.85 3.08 15.07 2.19 24.46 3.69 1.68 7.79 0.91 5.65

0.7854 0.8578 0.6149 1.3260 0.8424 0.8165 0.8486 0.7549 0.7756 0.9778 0.6816 0.6103 0.7002 0.9756 0.8416 0.9602 0.7569 0.9136 0.9309 0.6534 0.8233

110.15 106.50 104.55 34.90 114.86 108.42 110.98 108.55 55.26 161.64 80.31 136.26 114.41 85.38 2.47 169.76 38.02 16.26 33.81 79.36 114.49

128.52 133.35 133.39 135.23 139.03 139.18 139.98 139.99 140.28 330.69 150.73 150.74 154.42 154.57 335.40 155.38 155.37 154.46 155.51 155.52 156.31

131.77 150.45 187.19 175.91 150.18 149.90 145.48 137.33 119.75 66.00 203.39 262.19 143.48 286.98 115.36 198.98 139.70 322.17 267.57 37.24 177.45

4.23 1.31 358.50 0.69 4.35 9.51 1.60 4.34 10.45 359.77 356.64 321.86 7.58 174.68 347.14 179.57 3.98 343.43 358.18 91.37

189

0.17


0230 0231* 0232 0233 0234 0235 0236 0237 0238 0239 0240 0241 0242 0243* 0244 0245* 0246 0247 0248 0249 0250

2006/08/29 2006/09/07 2006/09/08 2006/09/08 2006/09/08 2006/09/08 2006/09/09 2006/09/09 2006/09/09 2006/09/09 2006/09/10 2006/09/10 2006/09/15 2006/09/15 2006/09/16 2006/09/17 2006/09/17 2006/09/18 2006/09/18 2006/09/19 2006/09/21

22:57:56 02:27:46 00:17:10 02:10:18 02:17:01 22:33:28 00:05:48 03:21:39 21:46:29 23:54:39 00:00:12 01:42:02 00:38:52 01:39:07 02:07:49 22:19:15 22:45:04 01:43:55 02:34:32 03:58:57 20:06:16

77.42 82.38 335.65 45.29 74.97 304.75 105.48 103.59 53.43 46.92 5.84 57.33 74.06 74.78 359.48 296.17 78.67 87.21 74.88 51.23 338.74

56.39 13.57 -4.89 39.41 32.76 64.60 37.47 38.75 33.45 38.79 10.69 5.08 56.44 32.65 2.99 78.88 28.92 23.82 29.26 63.92 29.74

59.49 65.33 15.80 62.71 69.52 30.51 63.59 62.12 57.85 59.98 37.27 61.63 31.30 66.65 20.13 36.83 78.73 68.84 47.66 52.49 24.62

59.79 65.52 16.54 61.05 67.86 29.84 64.22 60.88 65.60 59.95 36.54 64.42 47.60 68.27 20.67 36.95 75.86 67.81 64.26 52.63 25.68

0.8746 0.9143 0.7533 0.6853 0.9960 0.9682 0.5235 0.5279 0.6484 0.6411 0.1525 0.6399 0.5029 0.9733 0.5261 0.9970 0.9860 0.9922 0.5609 0.8847 0.7089

4.88 2.35 2.22 3.90 5.27 6.80 10.51 3.04 2.22 2.23 2.75 3.42 0.82 3.45 1.58 19.55 -1.61 3.32 1.30 3.45 6.99

0.8207 0.6110 0.6609 0.8241 0.8111 0.8576 0.9502 0.8265 0.7075 0.7125 0.9446 0.8131 0.3878 0.7178 0.6671 0.9490 1.6122 0.7008 0.5685 0.7436 0.8986

119.89 161.44 0.29 137.37 162.94 47.54 148.42 145.36 152.71 138.39 15.06 148.98 95.04 162.81 0.10 59.80 171.02 179.82 165.93 100.13 24.14

156.37 344.25 345.60 165.21 165.22 166.03 166.10 166.23 166.98 166.09 167.05 347.13 171.95 172.00 171.47 174.78 174.82 175.50 174.96 175.99 178.60

136.21 321.18 67.19 252.43 172.34 201.39 91.25 87.48 264.01 262.10 318.14 78.91 346.86 200.66 282.14 186.28 192.26 169.39 287.09 223.15 247.37

2.72 7.93 347.50 354.56 0.53 359.15 1.21 8.25 338.98 346.62 352.42 352.66 198.54 357.34 335.57 359.95 -3.59 1.47 284.10 355.42

190

357.96


0251 0252* 0253 0254 0255 0256 0257* 0258 0259 0260 0261 0262 0263 0264 0265 0266 0267 0268* 0269 0270 0271

2006/09/22 2006/09/23 2006/09/23 2006/09/23 2006/09/25 2006/09/25 2006/09/26 2006/09/26 2006/09/27 2006/09/27 2006/09/29 2006/09/29 2006/09/29 2006/09/30 2006/09/30 2006/09/30 2006/09/30 2006/10/02 2006/10/07 2006/10/09 2006/10/10

20:20:34 00:14:25 00:18:50 01:08:12 22:08:44 23:57:11 00:29:35 01:34:56 02:43:30 23:49:22 20:04:44 22:07:34 22:16:34 03:55:50 04:14:39 04:55:10 04:56:22 22:30:42 04:53:39 22:31:30 01:14:17

355.54 86.50 72.83 167.70 40.23 259.51 82.04 55.45 63.40 95.04 331.17 348.77 354.52 103.51 73.73 53.37 65.26 21.77 168.69 13.13 33.41

11.97 28.96 41.01 48.85 32.39 61.66 33.64 34.34 45.85 42.15 4.09 27.31 2.64 13.32 16.74 45.95 16.10 10.83 13.59 -0.53 3.35

20.54 66.24 62.90 44.38 58.28 25.77 65.69 36.37 58.71 67.45 13.18 18.52 14.40 66.40 61.69 48.52 50.49 29.61 46.12 15.05 32.49

20.98 67.03 65.36 44.41 55.59 25.96 66.57 54.81 59.73 66.63 13.51 19.08 13.85 67.76 63.80 57.45 49.12 28.25 46.64 20.16 33.17

0.5722 0.9894 0.8394 0.5077 0.1822 0.9949 0.9019 0.1532 0.6219 0.9998 0.8918 0.7216 0.7701 0.9517 0.5237 0.3894 0.1157 0.3059 0.0573 0.6859 0.2888

1.89 2.33 3.11 25.77 -12.23 12.09 2.74 1.33 2.94 5.19 3.27 2.12 1.79 2.99 2.49 2.77 0.97 1.91 13.02 1.92 3.05

0.6969 0.5761 0.7303 0.9803 1.0149 0.9177 0.6704 0.8845 0.7885 0.8074 0.7274 0.6590 0.5690 0.6816 0.7897 0.8596 0.8806 0.8402 0.9956 0.6426 0.9054

6.29 170.60 146.05 67.70 121.85 38.45 161.43 116.64 129.20 147.85 2.67 15.54 0.88 162.38 166.62 111.86 158.87 1.23 36.44 6.08 16.35

179.57 179.76 179.75 179.78 182.60 181.69 182.70 182.74 183.77 183.65 186.38 186.52 6.69 6.76 6.77 186.80 6.80 99.45 193.69 16.41 16.51

272.42 193.07 231.96 90.32 308.71 171.62 220.94 328.47 261.84 178.56 222.07 252.60 68.36 331.70 94.70 290.47 152.74 211.42 27.19 78.82 119.77

342.10 357.24 353.20 0.30 178.57 0.15 353.52 310.40 351.48 0.11 355.21 345.98 341.66 4.21 348.36 345.15 318.28 344.28 0.64 342.50

191

352.75


0272 0273 0274 0275 0276 0277 0278 0279* 0280 0281* 0282* 0283 0284 0285 0286* 0287 0288 0289 0290 0291 0292*

2006/10/10 2006/10/10 2006/10/10 2006/10/11 2006/10/12 2006/10/13 2006/10/14 2006/10/14 2006/10/16 2006/10/19 2006/10/19 2006/10/20 2006/10/23 2006/10/23 2006/10/24 2006/10/24 2006/10/24 2006/10/24 2006/10/24 2006/10/24 2006/10/24

01:19:48 02:21:33 02:22:33 20:26:49 20:38:52 01:26:42 19:24:59 19:39:52 03:36:17 00:12:06 23:41:36 01:09:47 23:32:19 23:38:01 00:03:24 00:29:16 00:59:44 01:40:41 02:43:34 05:24:20 21:36:50

4.50 88.58 231.63 37.50 101.18 308.68 62.86 16.70 39.36 93.32 92.39 94.29 93.84 97.56 96.99 98.24 97.97 26.60 97.37 96.45 134.12

75.64 16.25 49.36 12.69 63.88 47.23 78.97 65.89 12.99 16.01 16.38 15.60 18.29 15.01 15.71 15.23 16.26 14.20 15.69 15.40 39.31

37.77 67.41 22.78 32.08 48.98 13.78 48.67 37.26 28.04 65.17 66.88 62.79 58.89 63.48 64.69 62.02 65.30 21.20 56.03 64.58 67.90

37.02 66.99 24.12 33.83 49.59 13.92 46.19 40.64 30.07 63.84 65.52 62.17 63.84 66.89 66.52 63.12 66.42 21.37 65.25 57.39 68.58

0.8812 0.7244 0.9079 0.1877 0.8780 0.9861 0.8984 0.7311 0.2766 0.5806 0.5929 0.5338 0.4204 0.6022 0.5712 0.5355 0.5916 0.6076 0.4510 0.4419 0.9860

5.14 6.37 4.09 1.78 1.37 2.62 320.86 16.00 1.66 3.49 8.45 2.24 2.35 4.49 6.56 2.27 6.06 2.49 2.22 2.33 19.07

0.8285 0.8862 0.7779 0.8943 0.3572 0.6230 0.9972 0.9543 0.8331 0.8335 0.9298 0.7615 0.8212 0.8658 0.9129 0.7646 0.9023 0.7558 0.7972 0.8104 0.9483

61.39 165.49 32.29 7.56 102.50 18.70 80.24 59.74 4.82 163.52 164.43 162.21 166.81 161.91 163.11 161.73 164.71 0.70 161.62 160.75 144.49

196.51 16.54 196.54 18.30 199.28 199.46 201.21 201.22 22.56 25.37 25.35 26.40 29.32 29.32 30.34 30.36 30.38 210.26 30.45 30.56 211.24

222.46 65.58 142.14 136.09 237.59 195.44 217.28 243.68 126.26 85.61 81.12 94.50 107.35 82.16 84.33 94.16 82.05 265.08 106.48 105.93 166.46

357.57 357.69 3.27 344.09 332.19 357.35 179.31 267.44 340.58 353.38 358.18 346.58 345.59 354.50 357.05 346.86 357.19 348.91 337.94 342.55

192

0.18


0293 0294 0295* 0296 0297* 0298 0299 0300 0301 0302* 0303* 0304 0305 0306 0307 0308 0309 0310 0311 0312 0313

2006/10/24 2006/10/24 2006/10/26 2006/10/27 2006/11/06 2006/11/08 2006/11/09 2006/11/09 2006/11/09 2006/11/09 2006/11/09 2006/11/09 2006/11/11 2006/11/13 2006/11/14 2006/11/18 2006/11/19 2006/11/19 2006/11/19 2006/11/19 2006/11/19

22:17:02 23:33:05 22:41:19 21:42:14 00:19:55 23:24:32 00:11:03 00:44:59 01:06:04 03:11:42 04:32:59 05:14:20 21:22:48 04:56:27 05:59:14 02:25:03 04:12:25 04:18:16 04:46:01 05:41:04 05:41:05

113.14 44.50 21.66 49.21 120.36 156.54 35.90 56.84 218.54 148.51 193.17 117.41 56.05 176.21 151.42 151.59 154.25 217.17 187.08 88.11 154.28

49.47 14.90 10.55 -3.16 46.97 45.18 27.29 23.69 76.59 28.92 29.18 7.17 16.63 12.96 24.51 -3.76 21.68 73.43 15.28 76.12 21.53

58.93 29.19 18.52 29.39 59.84 53.09 16.95 28.00 32.31 68.84 52.13 69.70 26.01 63.90 70.21 69.57 70.09 30.96 62.67 34.51 69.34

61.81 29.21 18.59 30.88 65.38 61.18 15.61 29.27 34.66 66.43 50.95 74.19 25.82 63.16 67.57 70.43 69.15 31.81 61.93 31.43 70.56

0.8407 0.2894 0.7116 0.4344 0.7067 0.9733 0.7001 0.3318 0.9982 0.9806 0.4200 0.7876 0.4185 0.3807 0.9901 0.9245 0.9967 0.9971 0.3814 0.7265 0.9971

2.52 1.79 2.71 2.86 -43.62 1.78 1.70 1.99 2.36 3.95 5.38 -2.71 1.98 9.84 4.62 77.69 5.29 1.91 158.92 2.15 6.19

0.6667 0.8379 0.7370 0.8482 1.0162 0.4545 0.5885 0.8330 0.5773 0.7518 0.9219 1.2902 0.7883 0.9613 0.7859 0.9881 0.8116 0.4767 0.9976 0.6624 0.8389

129.04 4.58 1.14 26.41 129.20 120.49 5.29 3.27 58.11 153.39 93.75 154.50 5.31 154.45 159.22 154.07 162.33 55.36 137.39 53.32 162.61

211.27 30.35 33.39 34.24 223.35 226.32 226.32 226.33 226.39 226.48 226.53 46.56 49.28 230.57 231.62 55.50 236.59 236.59 236.61 236.64 236.65

233.36 123.94 71.20 103.44 250.48 151.68 259.05 298.10 185.72 162.75 77.91 51.74 108.58 74.71 167.76 327.99 173.12 187.61 76.19 251.91 173.53

350.28 342.68 350.80 351.29 72.00 15.96 338.79 345.04 358.81 2.10 3.35 -6.47 344.15 1.31 1.13 0.18 0.45 357.75 0.21 345.97

193

0.34


0314 0315 0316* 0317 0318 0319 0320 0321* 0322 0323* 0324 0325* 0326 0327 0328 0329 0330 0331 0332* 0333 0334

2006/11/20 2006/11/20 2006/11/21 2006/11/21 2006/11/24 2006/11/24 2006/11/24 2006/11/24 2006/11/24 2006/11/25 2006/11/25 2006/11/26 2006/11/26 2006/11/26 2006/11/26 2006/11/27 2006/11/28 2006/11/28 2006/11/29 2006/11/29 2006/11/29

02:22:07 04:27:23 04:59:52 05:25:12 02:19:56 02:33:29 02:53:01 04:20:15 04:53:23 00:13:16 06:05:45 05:17:50 05:21:07 05:22:23 06:30:02 03:54:30 00:20:42 04:46:35 01:17:59 04:12:10 04:22:26

169.77 155.22 155.60 132.27 160.62 73.88 138.27 133.97 141.87 340.27 155.70 75.39 239.25 161.90 190.22 126.84 69.36 127.28 134.53 177.16 70.77

20.08 21.68 21.27 25.37 49.97 24.85 25.08 7.92 22.66 55.61 42.96 17.48 80.94 20.87 40.28 21.74 15.67 31.83 27.00 31.85 27.35

44.65 68.10 66.94 47.56 48.73 28.49 62.41 68.11 57.63 16.21 46.68 26.00 29.94 69.46 56.33 54.87 23.34 56.62 62.99 48.05 25.62

55.93 68.53 63.41 59.21 56.92 28.05 63.44 68.29 55.01 16.34 55.55 26.18 29.71 53.75 57.85 52.98 22.65 56.79 61.38 60.39 24.93

0.3277 0.9970 0.9979 0.2976 0.8982 0.3371 0.6208 0.7477 0.4651 0.9797 0.6792 0.4062 0.9698 0.7641 0.9001 0.1621 0.5199 0.2359 0.4245 0.7435 0.4854

0.87 3.33 1.78 1.09 1.69 1.91 1.85 8.94 0.93 4.79 1.12 1.86 2.89 1.76 5.73 1.18 1.96 2.05 2.90 1.30 2.48

0.6234 0.7008 0.4405 0.7258 0.4677 0.8232 0.6645 0.9163 0.5006 0.7953 0.3926 0.7815 0.6642 0.5651 0.8429 0.8627 0.7350 0.8851 0.8536 0.4283 0.8039

142.69 161.51 161.26 160.68 107.95 1.49 162.45 162.12 163.95 20.27 116.34 7.39 49.18 156.31 107.51 172.61 6.78 143.05 157.94 123.75 3.29

237.52 237.61 238.64 238.66 241.56 241.49 241.59 61.63 241.67 242.47 242.73 63.72 243.70 243.71 243.76 244.67 65.54 245.71 246.58 246.70 246.66

37.33 173.16 173.15 315.78 232.48 297.98 267.18 61.89 307.41 197.43 281.75 110.69 202.43 91.05 141.36 324.13 97.65 308.87 284.54 88.69 278.94

87.58 0.89 2.85 301.51 333.89 343.94 341.19 358.36 288.86 358.84 293.60 342.51 356.62 82.85 2.05 328.60 343.38 346.80 351.25 69.07

194

348.86


0335 0336 0337* 0338* 0339 0340 0341* 0342* 0343 0344 0345 0346* 0347 0348 0349 0350 0351* 0352* 0353 0354* 0355

2006/11/29 2006/11/29 2006/12/01 2006/12/01 2006/12/04 2006/12/04 2006/12/05 2006/12/06 2006/12/07 2006/12/08 2006/12/08 2006/12/09 2006/12/09 2006/12/11 2006/12/11 2006/12/11 2006/12/11 2006/12/12 2006/12/12 2006/12/12 2006/12/12

06:02:17 06:30:31 05:18:16 23:13:37 00:36:02 06:20:30 03:06:54 05:52:37 06:07:53 02:55:07 04:19:54 01:17:37 06:05:47 04:51:10 04:59:14 20:24:34 23:01:38 00:08:08 00:14:59 01:10:10 01:30:36

195.54 308.44 137.75 209.66 329.66 128.33 125.91 87.31 160.44 151.44 187.00 99.52 109.47 199.06 127.38 97.14 146.41 111.98 109.85 111.34 110.69

76.49 60.38 -22.06 57.45 59.97 1.09 22.52 18.02 -14.65 43.48 13.53 9.11 34.42 9.93 1.60 34.93 47.20 33.44 33.69 33.73 33.71

38.10 19.68 61.49 36.92 17.46 62.38 57.16 25.52 62.63 59.83 52.58 42.23 33.14 57.78 60.09 36.12 50.58 30.45 33.11 30.66 32.97

37.96 19.58 60.83 40.36 17.53 58.89 57.38 26.35 63.47 60.09 62.22 38.52 32.59 55.31 54.09 32.02 53.79 32.53 32.00 33.67 32.48

0.9531 0.9977 0.9558 0.9731 0.9936 0.4084 0.1145 0.3932 0.9887 0.6368 0.5497 0.1824 0.1489 0.3921 0.2467 0.2548 0.4607 0.1507 0.1589 0.1548 0.1554

4.52 11.60 17.60 1.80 5.85 5.35 3.51 1.70 2.00 14.25 1.25 4.86 1.21 1.37 7.34 2.64 3.06 1.09 1.24 1.17 1.23

0.7893 0.9140 0.9457 0.4606 0.8302 0.9237 0.9674 0.7681 0.5056 0.9553 0.5611 0.9625 0.8769 0.7134 0.9664 0.9035 0.8495 0.8621 0.8715 0.8671 0.8739

63.39 26.20 116.09 70.59 22.97 136.27 168.47 7.93 140.65 118.17 147.19 35.25 23.76 139.95 124.66 17.68 101.01 21.96 22.06 22.75 22.78

246.77 246.78 68.77 249.53 251.60 71.85 252.74 73.88 74.88 255.77 255.83 76.72 256.91 258.90 78.90 259.55 259.67 259.71 259.71 259.75 259.77

206.66 185.67 24.61 153.86 189.63 103.72 323.23 113.38 345.11 255.14 71.82 131.88 325.27 62.43 122.86 304.80 280.35 326.60 323.74 325.10 324.21

358.04 359.91 359.74 13.25 359.54 355.72 354.99 339.63 4.34 359.29 52.53 265.88 330.89 30.76 174.97 350.80 351.09 325.18 331.65 328.75

195

331.58


0356 0357 0358 0359 0360* 0361 0362* 0363 0364 0365* 0366 0367* 0368 0369 0370 0371 0372 0373 0374 0375 0376

2006/12/12 2006/12/15 2006/12/16 2006/12/16 2006/12/16 2006/12/16 2006/12/21 2006/12/22 2006/12/23 2006/12/23 2006/12/23 2006/12/23 2006/12/23 2006/12/31 2006/12/31 2006/12/31 2006/12/31 2006/12/31 2007/01/08 2007/01/08 2007/01/15

23:16:10 20:42:06 03:43:18 04:32:34 05:34:17 21:33:27 03:43:37 22:43:57 00:05:00 00:48:35 01:08:29 02:26:22 03:06:44 00:39:46 01:51:44 03:00:22 03:34:33 03:47:06 01:48:24 04:13:14 22:25:29

111.87 138.11 93.78 203.22 188.34 82.57 160.08 214.38 237.38 283.51 140.12 121.11 141.36 169.82 131.68 53.17 146.50 203.77 215.07 229.32 202.27

32.65 55.83 26.91 5.73 16.25 18.19 -3.24 77.50 68.31 56.12 -4.63 12.18 -10.53 41.21 40.58 75.49 -8.89 14.40 76.93 45.64 51.04

32.52 45.10 23.14 61.12 66.48 19.76 71.03 33.00 32.71 19.72 54.80 38.24 58.13 55.03 39.64 13.18 53.32 63.49 21.38 50.43 45.94

33.61 45.29 25.35 63.57 67.67 20.23 69.13 32.25 32.92 19.56 55.79 37.76 57.87 52.61 38.77 13.40 57.86 64.36 23.76 44.78 50.93

0.1405 0.4715 0.4489 0.4903 0.9524 0.6075 0.8062 0.9496 0.9972 0.9761 0.2852 0.0938 0.4565 0.5380 0.2526 0.9516 0.3170 0.9465 0.9517 0.9937 0.8661

1.21 4.00 1.74 3.03 4.15 1.84 -32.64 4.46 3.98 2.57 2.44 1.55 4.78 4.57 3.47 1.92 3.21 2.56 1.73 18.03 99.55

0.8837 0.8822 0.7426 0.8384 0.7704 0.6701 1.0247 0.7869 0.7497 0.6202 0.8832 0.9395 0.9045 0.8824 0.9271 0.5045 0.9011 0.6296 0.4509 0.9449 0.9913

21.82 75.05 1.79 148.07 147.94 5.26 159.44 52.22 53.88 29.83 122.41 27.04 119.63 101.95 43.53 17.69 118.46 139.56 37.70 80.85 81.20

260.69 263.64 263.86 263.97 264.01 84.71 89.02 270.85 270.91 270.93 90.95 91.01 91.03 279.08 279.13 279.17 99.21 279.22 287.28 287.38 295.29

326.34 277.33 287.16 83.06 152.80 88.73 52.18 207.69 186.56 159.72 121.63 150.57 98.30 269.30 303.62 211.16 116.58 149.49 212.46 170.65 223.35

331.13 354.87 340.03 8.67 3.00 341.28 177.98 357.91 359.42 3.92 349.56 342.25 356.13 355.38 354.20 351.14 351.66 5.69 348.75 0.70

196

177.75


0377 0378* 0379* 0380 0381 0382 0383 0384 0385 0386 0387 0388 0389 0390 0391 0392 0393 0394 0395 0396 0397

2007/01/15 2007/01/16 2007/01/17 2007/01/17 2007/01/17 2007/01/17 2007/01/20 2007/02/03 2007/02/06 2007/02/13 2007/02/18 2007/02/18 2007/02/26 2007/03/02 2007/03/02 2007/03/02 2007/03/03 2007/03/04 2007/03/05 2007/03/09 2007/03/09

23:35:16 05:23:42 05:11:43 05:19:38 05:51:02 06:20:48 03:14:47 01:37:30 20:38:12 06:35:57 05:00:16 05:02:28 05:47:25 04:59:01 05:33:00 19:42:41 21:07:47 23:09:29 05:09:38 02:23:43 02:48:47

193.25 278.38 164.02 302.13 287.61 211.76 132.88 33.19 138.75 195.51 244.38 223.03 224.65 198.21 239.66 357.82 185.15 275.68 232.67 192.33 249.03

56.10 37.42 26.73 72.60 20.88 26.33 16.69 38.98 48.94 4.12 8.85 13.34 -25.20 28.94 32.54 45.38 37.08 61.17 7.53 4.56 57.82

37.94 75.30 41.33 16.11 31.03 58.78 23.17 73.97 29.83 59.30 62.31 54.55 64.91 38.59 37.89 13.80 29.92 18.19 59.72 35.69 27.55

44.98 51.74 60.38 16.11 29.80 57.39 19.21 78.78 22.38 58.46 63.77 66.23 65.20 38.21 32.77 14.25 30.21 22.93 60.73 36.08 28.28

0.7946 0.8598 0.1556 1.0000 0.6948 0.9658 0.4622 1.0000 0.7408 0.1521 0.9974 0.6845 0.6915 0.4305 0.7251 0.9115 0.6099 0.9844 0.6162 0.1763 0.9856

4.59 -0.31 -6.59 2.40 35.45 2.76 1.30 -0.10 -41.39 11.98 4.01 7.13 2.51 4.59 1.05 2.42 4.68 1.46 4.07 2.08 2.29

0.8267 3.7704 1.0236 0.5838 0.9804 0.6496 0.6441 11.1855 1.0179 0.9873 0.7514 0.9040 0.7243 0.9062 0.3068 0.6238 0.8697 0.3255 0.8487 0.9152 0.5691

68.54 65.90 85.54 24.37 34.24 115.28 2.90 17.20 21.48 144.61 128.82 123.20 162.84 49.99 70.35 14.46 32.59 36.35 126.41 16.55 47.03

295.34 295.58 296.60 296.59 296.62 296.65 119.62 313.72 317.57 324.07 329.05 329.05 157.13 341.12 341.15 341.73 342.80 343.89 344.14 348.02 348.04

237.82 144.80 314.76 180.44 112.54 204.12 111.95 180.24 241.35 314.99 173.74 254.27 74.60 281.42 281.27 140.33 260.71 158.70 260.59 316.36 196.20

173.75 81.88 160.16 0.08 0.34 355.96 325.62 2.33 175.44 359.14 0.64 164.10 349.28 355.91 292.52 7.86 356.03 11.53 354.94 347.85

197

356.41


0398* 0399 0400 0401 0402* 0403 0404 0405 0406 0407 0408 0409 0410 0411 0412 0413 0414 0415 0416 0417 0418

2007/03/18 2007/03/19 2007/03/20 2007/03/25 2007/03/26 2007/03/28 2007/03/29 2007/03/29 2007/03/29 2007/04/02 2007/04/04 2007/04/04 2007/04/05 2007/04/05 2007/04/17 2007/06/18 2007/07/30 2007/08/02 2007/08/02 2007/08/02 2007/08/03

03:42:56 21:36:54 01:21:13 23:19:21 02:24:00 00:57:25 01:44:02 03:19:05 03:45:44 04:49:19 21:17:09 23:04:29 00:41:36 01:00:09 04:22:16 02:03:30 23:02:30 23:10:32 23:20:46 23:46:56 01:51:34

258.18 244.51 220.70 171.72 240.16 300.32 286.28 301.78 263.79 284.04 204.75 225.89 268.39 187.35 331.50 295.44 283.44 32.98 339.00 16.48 32.27

21.43 34.19 30.12 52.27 35.01 69.50 38.04 -2.06 -0.35 77.67 5.93 79.15 45.22 3.26 17.82 -24.16 12.36 58.92 -14.36 29.36 52.79

55.36 43.29 39.70 18.10 31.37 20.69 46.64 47.83 58.76 18.38 26.63 16.51 36.31 19.13 65.40 18.86 15.01 57.42 34.79 63.43 58.00

55.00 44.65 40.57 18.67 39.77 21.64 45.80 55.43 57.60 18.58 26.20 17.53 37.36 15.82 42.49 54.94 16.46 56.90 39.70 64.54 55.58

0.9540 0.8380 0.5866 0.9326 0.7445 0.9742 0.9609 0.2921 0.7483 0.9953 0.4488 1.0000 0.9893 0.7168 0.3446 0.1794 0.8554 0.9287 0.1163 0.8721 0.9470

5.04 3.52 7.61 9.54 1.96 2.44 11.75 1.14 1.44 2.83 1.99 2.67 2.73 1.96 -2.21 0.99 2.61 36.00 1.97 3.83 3.08

0.8108 0.7616 0.9229 0.9022 0.6199 0.6005 0.9182 0.7428 0.4797 0.6480 0.7743 0.6248 0.6378 0.6348 1.1560 0.8189 0.6717 0.9742 0.9410 0.7721 0.6928

103.18 76.59 59.13 18.58 60.80 33.62 79.34 134.03 135.05 28.15 13.14 25.66 64.23 0.68 98.90 25.49 13.15 106.81 19.29 142.95 114.13

357.06 358.80 358.95 3.83 4.95 6.87 7.89 7.96 7.98 11.96 14.61 13.70 14.76 14.48 27.49 267.22 126.33 129.21 309.22 129.24 130.28

206.24 231.35 262.03 210.91 252.70 158.63 156.68 47.14 257.19 171.11 285.26 180.58 193.47 254.72 69.79 148.23 230.22 148.83 145.38 225.10 150.39

358.25 354.84 358.09 359.29 339.67 4.49 0.44 45.13 330.52 1.57 344.10 0.04 357.74 343.63 32.40 132.96 351.97 0.12 347.79 355.87

198

4.39


0419 0420 0421 0422 0423 0424 0425* 0426 0427 0428 0429 0430 0431* 0432 0433 0434 0435 0436* 0437 0438 0439

2007/08/06 2007/08/06 2007/08/06 2007/08/06 2007/08/12 2007/08/13 2007/08/13 2007/08/13 2007/08/13 2007/08/13 2007/08/13 2007/08/13 2007/08/13 2007/08/14 2007/08/15 2007/08/19 2007/12/08 2007/12/08 2007/12/08 2007/12/13 2007/12/13

00:03:05 00:41:54 01:22:38 01:46:26 22:51:39 02:43:57 02:47:45 02:56:42 03:11:15 03:14:57 03:17:21 03:25:05 03:26:48 02:29:02 02:45:09 22:43:08 19:51:30 20:57:24 23:32:18 23:20:59 23:53:03

334.78 39.22 23.29 341.44 57.67 47.94 47.88 46.67 64.36 48.83 46.24 44.29 45.34 49.97 50.55 305.68 70.02 98.26 105.99 111.64 110.10

38.62 56.56 18.94 49.75 59.64 57.70 57.86 57.47 56.48 36.28 57.88 59.85 57.52 58.31 57.72 65.49 16.94 8.77 30.74 32.97 33.29

33.69 49.29 58.32 52.26 57.93 50.16 36.73 52.41 51.91 50.91 58.70 73.32 50.12 50.36 58.01 34.21 17.46 39.13 31.40 30.05 25.22

36.36 57.32 66.58 46.04 57.06 58.71 40.62 56.96 44.18 60.27 59.12 47.78 56.31 50.88 58.72 26.76 18.78 41.13 28.31 30.89 39.26

0.5444 0.8812 0.6995 0.8439 0.8474 0.8950 0.5624 0.9178 0.5824 0.7101 0.9433 0.9266 0.9130 0.8607 0.9294 0.9769 0.6591 0.1901 0.1618 0.1714 0.1829

1.39 2.22 2.01 -20.84 10.82 2.53 1.32 2.43 1.31 1.10 14.12 -2.47 2.00 1.48 6.77 3.48 1.78 4.64 1.06 1.11 1.23

0.6074 0.6038 0.6519 1.0405 0.9217 0.6457 0.5748 0.6226 0.5552 0.3536 0.9332 1.3749 0.5437 0.4171 0.8627 0.7193 0.6290 0.9590 0.8473 0.8459 0.8510

62.82 108.01 163.59 84.41 110.09 109.62 81.62 110.27 103.60 144.15 112.85 108.97 108.67 106.13 113.50 50.59 5.63 36.14 13.36 18.64 21.12

133.07 133.10 133.13 133.14 139.74 139.89 139.89 139.90 139.91 139.92 139.92 139.92 139.92 140.85 141.82 146.46 76.25 76.28 256.37 261.45 261.47

282.04 130.09 259.95 226.58 132.97 134.05 69.33 141.01 78.00 80.23 151.96 141.96 136.21 121.76 147.93 199.63 83.27 130.89 325.88 323.93 321.49

328.01 16.76 334.35 176.73 0.90 14.32 84.45 9.12 42.82 77.49 0.38 24.21 16.23 24.32 1.29 356.83 340.13 356.30 322.68 325.26

199

331.14


0440 0441 0442 0443 0444 0445 0446* 0447 0448 0449* 0450* 0451 0452 0453 0454 0455 0456 0457

2007/12/14 2007/12/14 2007/12/14 2007/12/14 2007/12/14 2007/12/14 2007/12/14 2007/12/15 2007/12/15 2007/12/15 2007/12/20 2007/12/22 2007/12/22 2007/12/22 2007/12/22 2007/12/23 2007/12/23 2007/12/23

01:01:26 01:15:52 02:00:33 05:01:16 06:23:46 21:06:17 23:34:47 00:33:51 03:04:55 03:07:22 18:51:34 18:56:49 20:44:54 22:00:40 23:08:38 01:31:06 04:03:37 05:40:03

112.93 113.16 113.61 113.89 114.68 118.61 113.94 113.70 113.94 117.42 291.32 223.04 217.80 215.20 237.42 213.39 215.40 95.79

33.12 33.22 33.11 32.93 33.22 29.24 32.76 31.95 30.16 33.45 38.19 76.38 77.21 76.57 74.05 53.25 75.61 27.06

36.58 29.30 34.02 31.26 31.85 28.47 32.64 31.10 31.59 28.97 15.25 32.60 33.56 34.02 25.35 42.45 33.43 23.57

33.86 33.17 33.34 32.27 27.71 32.01 32.95 34.08 22.53 33.95 15.73 32.84 32.92 33.67 28.13 43.59 32.66 23.13

0.1337 0.1629 0.1415 0.1594 0.1764 0.1094 0.1457 0.1469 0.2003 0.1494 0.9385 0.9583 0.9524 0.9523 0.9856 0.9995 0.9548 0.5345

1.40 1.12 1.26 1.17 1.07 0.90 1.20 1.20 0.97 1.06 2.09 4.27 5.01 5.41 2.04 2.57 4.81 2.22

0.9046 0.8548 0.8878 0.8637 0.8346 0.8778 0.8785 0.8773 0.7925 0.8586 0.5520 0.7756 0.8100 0.8239 0.5170 0.6107 0.8015 0.7592

25.88 20.96 24.09 20.48 18.44 15.66 22.19 20.29 11.88 24.01 20.84 52.75 53.12 54.10 45.37 77.06 52.91 1.00

261.52 261.53 261.56 261.69 261.74 262.37 262.48 262.52 262.62 262.63 268.38 270.43 270.50 270.56 270.60 270.71 270.81 270.70

325.49 324.77 325.64 324.48 324.20 334.88 325.75 325.67 324.34 327.35 145.78 205.23 206.66 206.55 196.78 180.93 206.06 274.68

337.87 326.31 333.19 328.73 322.47 312.95 330.61 330.53 314.08 323.27 8.91 357.96 358.32 358.52 355.42 179.95 358.25 346.52

200