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Planetary and Space Science 56 (2008) 1847 ­ 1850 www.elsevier.com/locate/pss

An accuracy estimation of the World CCD asteroid observations in the years 1999­2005
O.P. Bykovö, V.N. L'vov, I.S. Izmailov, G.R. Kastel
Central Astronomical Observatory of RAS, Pulkovskoye shosse 65/1, 196140 Saint-Petersburg, Russia Accepted 5 February 2008 Available online 23 July 2008

Abstract The MPC database of the asteroid observations (each position from near 20 millions) was used in analysis of observational accuracy for more than 300 active world observatories both professional and amateur. The values of the ``Mean error of a single observation'' s (for a; d) were derived based on the Pulkovo method of accuracy estimation. These values may be used for observatory weight assignment in the orbital improvement procedures. The accuracy of the best amateur observations is proved to be comparable with professional one (s ¼ ô000 :20). The detailed results in electronic format are accessible from the first author. r 2008 Published by Elsevier Ltd.
Keywords: Astrometric CCD observations; Asteroids

1. Introduction Usually an accuracy of positional asteroid and comet observations carried out with various telescopes in the world during different observational campaigns is obtained as a result of orbital improvement for these celestial bodies. The residuals of ÏO þ C÷, i.e, observational minus calculational positions for each observatory and each asteroid are published in the Minor Planet circulars together with new system of elements. General accuracy estimations that describe numerically the observations of any observatory, both professional and amateur, are absent in MPC practice. Some advanced amateurs (the number of amateur observatories is strongly increasing now from month to month) want to know a quality of their asteroid observations every night and to compare their own accuracy parameters with the other ones. We are sure that a testing of obtained observations, their accuracy estimation and identification of observed celestial objects must be carried out by observer himself immediately at the place of observation.

2. MPC database The Minor Planet Center supported by the International Astronomical Union is the main office for keeping observational data of the solar system minor bodies and their investigations. The MPC circulars that contain the CCD observations obtained by amateurs and professional astronomers all over the world were available due to the courtesy of the Institute of Applied Astronomy, St.-Petersburg (Bykov et al., 2002). We investigated an accuracy of these observations. Our experience of extensive processing of the MPC data allows to conclude that CCD observations of the numbered and unnumbered asteroids have the errors, sometimes very significant. We can also note the systematic errors in presented positions that are usually connected with CCD matrix work in the fixed nights of observations. Positions of the numbered minor planets (NMP) which have been sent by observers to the Minor Planet Center in the years 1999­2005 were automatically analyzed by means of calculation of ÏO þ C÷ values with the help of the EPOS software package created at Pulkovo Observatory (L'vov et al., 2001). More than 20 millions individual positions obtained by professional and amateur observatories were taken into consideration.

öCorresponding author.

E-mail address: oleg@OB3876.spb.edu (O.P. Bykov). 0032-0633/$ - see front matter r 2008 Published by Elsevier Ltd. doi:10.1016/j.pss.2008.02.032


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1848 O.P. Bykov et al. / Planetary and Space Science 56 (2008) 1847 ­1850 Table 2 CCD observations of NMP 78728 made by LONEOS (code 699) with large values of the mean errors of a single observation s Date 2006 08 27.43577 27.44487 27.45397 27.46310 a 23h 13m 25s 25s 25s 24s :900 :561 :021 :311 Ï O þ C÷ d ×7 040 4400 4200 4300 4400 :78 :39 :31 :22 Ï O þ C÷ Mgn Z


3. Method of accuracy estimation For reliable estimation of an accuracy of CCD observations obtained by given observatory we usually consider 10 and more various NMP observed during several months per year (more then 50 positions). It was postulated that the errors of the theory of motion of any numbered asteroid are smaller than the errors of their CCD observations. Therefore, the range of these ÏO þ C÷ values may be a good characteristic of observational accuracy. The real values of ÏO þ C÷ may be different but we study just the range of these values during several close nights by computation of the mean error of a single observation s. This value is placed at the last row of the table below the mean of ÏO þ C÷ values and its mean error. The other notations in the following tables are as follows: Mgn--the visual magnitude, Z--the zenith distance at the moment of observation. We use the EPOS software package for exact asteroid ephemeris calculations based on the latest catalogs of elements (usually ASTORB or MPCORB data) and full account for perturbation. It is important that one night of observations ought to have three or more positions of the NMP for calculation of the internal accuracy, and we use several close nights of observations of the same NMP for deriving the external accuracy (the corresponding symbols ``int'' and ``ext'' in the Tables 4 and 5). The examples of observational data and processing are given in Tables 1­3. Table 1 corresponds to very good professional positional CCD observations made by Tom Gehrels' group in Arizona University. Table 2 includes very large ÏO þ C÷ deviations for a and d during one night. Only observations are responsible for these changes. It is necessary in this situation to test the data by observer himself before sending them to the Minor Planet Center. As an example there are CCD observations of the same asteroid made by two Spacewatch Telescopes during one night presented in Table 3. These telescopes are situated near to each other. The mean values of ÏO þ C÷s for each coordinate are practically the same. Usually the Spacewatch Telescopes give good and similar results for the same asteroid.

þ000 :40 100 :38 000 :19 þ300 :52 þ000 :59 ô100 :04 200 :09

000 :55 þ100 :25 000 :24 100 :74 000 :32 ô000 :62 100 :23

19.0

40 42 45 47

Normal place 27.44943 25s :199 Its error: s

4300 :68

Table 3 One night CCD observations of NMP 69262 made by two Spacewatch Telescopes (codes 691 and 291) Code 691 Date 2006 08 19.33121 19.34852 19.36586 a 22h 54m 36s :464 35s :635 34s :806 Ï O þ C÷ d þ3 250 0000 :40 0000 :29 0000 :19 0000 :30 Ï O þ C÷ Mgn Z


þ000 :27 þ000 :24 þ000 :17 þ000 :23 ô000 :03 000 :05

000 :18 000 :17 000 :16 000 :17 ô000 :01 000 :01

17.0 17.3 17.3

36 35 35

Normal place 19.34853 35s :635 Its error: s Code 291 Date 2006 08 19.41532 19.41901 19.42277 a 22h 54m 32s :416 32s :249 32s :061

Ï O þ C÷

d þ3 240 5900 :93 5900 :93 5900 :94 5900 :93

Ï O þ C÷

Mgn

Z



þ000 :35 þ000 :20 þ000 :31 þ000 :29 ô000 :04 000 :08

000 :12 000 :09 000 :07 000 :09 ô000 :02 000 :03

40 41 42

Normal place 19.41904 32s :242 Its error: s

Table 1 CCD observations of NMP 82499 made by Spacewatch Telescope with normal values of the mean errors of a single observation s Date 2006 08 29.20449 29.22185 29.23927 a 22h 14m 32s :403 31s :649 30s :897 Ï O þ C÷ d þ4 280 2800 :62 3500 :40 4200 :08 3500 :37 ÏO þ C÷ Mgn Z


So we see that the ÏO þ C÷ values may be very different for various objects but their mean error shows a reliability of the system ``atmosphere × telescope× CCDcamera × catalogue ×method of astrometric reduction'' altogether atmean observational conditions. They are an indicator of accuracy of the CCD positional observations for a given observatory. 4. Results We are analyzing the sets of such mean error of a single observation s derived from all NMP observed at selected observatory during specified observational period. Then we calculate an average value for each set of these data. It may be considered as an accuracy of the

þ000 :17 þ000 :15 þ000 :06 þ000 :13 ô000 :03 000 :06

000 :26 000 :20 000 :27 000 :24 ô000 :02 000 :04

17.6 17.5 17.5

48 45 41

Normal place 29.22187 31s :650 Its error: s


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O.P. Bykov et al. / Planetary and Space Science 56 (2008) 1847 ­1850 Table 4 The best results of CCD asteroid observations from MPC database for some professional observatories MPC Observatory Code Professionals 673 Telescope 000 :07 0.07 0.08 0.06 000 :06 0.06 0.04 0.05 Year Total asteroids Total positions s
a

1849

sd

Type

USA, table Mountain, D ¼ 0:61 m, FL ¼ 9:0 m, FOV ¼ 22 á 220 , Scale ¼ 000 :3 USA, Kitt Peak, Spacewatch, D ¼ 0:88 m, FL ¼ 4:6 m, FOV ¼ 390 á 300 , Scale ¼ 100 :1

2004 2005

135 127 125 152

1344 1703 559 1015

int ext int ext

691

1999 2000 2001 2002 2003 2004 2005

1114 458 1898 635 4697 787 3856 680 20954 7553 28212 12397 35133 18707 11187 6397 36079 24683 33113 12776 35558 10630 39172 15508 20 6 11 4 17 4 25 7

5823 3408 10540 5261 19194 5389 14934 4440 101722 50350 154523 93942 219848 154816 103709 73522 309180 239812 190096 100669 183967 77005 260419 134088 144 98 52 24 135 68 219 89

0.23 0.40 0.20 0.34 0.22 0.38 0.21 0.33 0.20 0.33 0.18 0.25 0.23 0.26 0.19 0.45 0.20 0.30 0.18 0.23 0.18 0.23 0.16 0.18 0.16 0.19 0.05 0.05 0.12 0.12 0.12 0.09

0.26 0.34 0.21 0.31 0.20 0.34 0.22 0.38 0.18 0.38 0.17 0.23 0.23 0.26 0.19 0.50 0.20 0.37 0.18 0.29 0.16 0.19 0.15 0.16 0.15 0.20 0.07 0.12 0.10 0.11 0.10 0.07

int ext int ext int ext int ext int ext int ext int ext int ext int ext int ext int ext int ext int ext int ext int ext int int

644

USA, Palomar Mountain= NEAT, D ¼ 1:2 m, No data

2001 2002 2003 2004 2005

422

Australia, Loomberah. D ¼ 0:45 m, FL ¼ 2:4 m, FOV ¼ 17 á 170 , Scale ¼ 200 :

1999 2000 2001 2002 2003

investigated CCD observations. Of course we must have a lot of NMP observations for each observatory under consideration. As an advise for observers we would like to underline: if it is possible try to observe three positions per night and do not neglect to observe the Numbered Minor Planets in your telescope field of view as a ``by product'' of current observational programs. They are a good test for every-night estimation of your accuracy. We think such estimations ought to be produced every morning after CCD observations of the moving celestial objects by observer himself. Our analysis can find these errors too late. Obviously, it is desirable to test each asteroid's position before sending results to the MPC.

Tables 4,5 present an accuracy estimation for some professional and amateur telescopes carrying out the programs of observations of potentially hazardous asteroids. Finally, a difference between ``int'' and ``ext'' estimations may be explained by the influence of the reference star positions used for astrometric reduction. Usually one night asteroid images are processing with the same stars but several nights images demand other catalog's stars from night to night. We also noted that our accuracy parameters for the fast moving celestial bodies, such as NEO, are two times worse as compared to the usual objects. More detailed results can be found via Internet (www.accuracy.puldb.ru).


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1850 O.P. Bykov et al. / Planetary and Space Science 56 (2008) 1847 ­1850 Table 5 The best results of CCD asteroid observations from MPC database for some amateur observatories MPC Observatory Code Amateurs 621 Telescope 000 :21 0.22 0.14 0.22 0.24 0.28 0.30 0.30 0.36 0.37 0.32 0.31 0.32 0.33 0.14 0.37 0.08 0.37 0.16 0.40 0.12 0.50 0.12 0.35 0.12 0.21 0.13 0.26 0.23 0.22 0.18 0.17 0.15 000 :15 0.21 0.12 0.15 0.20 0.21 0.22 0.22 0.41 0.33 0.29 0.31 0.28 0.28 0.08 0.48 0.15 0.41 0.15 0.35 0.12 0.39 0.14 0.36 0.12 0.21 0.12 0.19 0.15 0.24 0.14 0.16 0.15 Year Total asteroids Total positions s
a

sd

Type

Germany, Bergisch Gladbach, D ¼ 0:6 m, FL ¼ 3:1 m, FOV ¼ 11 á 100 , Scale ¼ 100 :2

1999 2000 2001 2002 2003 2004 2005

17 17 22 19 73 55 102 61 241 101 183 83 262 83 8 12 7 6 19 21 32 34 55 45 29 15 31 26 35 95 7 111 4

125 134 152 156 480 455 649 493 1416 872 897 593 1106 556 36 61 38 34 106 147 186 230 447 424 204 150 285 262 153 494 64 594 43

int ext int ext int ext int ext int ext int ext int ext int ext int ext int ext int ext int ext int ext int ext int int ext int ext

127

Germany, Bornheim, D ¼ 0:19 m, FL ¼ 0:8 m, FOV ¼ 30 á 200 Scale ¼ 200 :4

1999 2000 2001 2002 2003 2004 2005

A34

Grosshabersdorf, Germany D ¼ 0:2 m, FL ¼ 2:0 m, FOV ¼ 20 á 150 Scale ¼ 100 :4

2003 2004 2005

5. Conclusions As we can see the accuracy of modern CCD asteroid observations is rather high. The best amateur astronomers work like the professionals. They could participate at the scientific observational campaigns to the benefit of Celestial Mechanics and Astrometry. We hope that the Pulkovo software package EPOS (http://neopage.nm.ru) will be useful for this work.

References
Bykov, O.P., L'vov, V.N., et al., 2002. Accuracy of positional CCD observations of numbered minor planets in 1999­2003 yrs. In: Proceedings of the Conference Asteroids, Comets, Meteors ACM 2002, pp. 413­417. L'vov, V.N., Smekhacheva, R.I., Tsekmejster, S.D., 2001. EPOS-- the program package for the Solar system objects research. In: Proceedings of the Conference Near Earth Astronomy in XXI Century, pp. 235­240.