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XMMнNewton CCF Release Note
XMMнCCFнRELн330
Astrometry: time variable boresight. A new update.
A. Talavera and P. RodrТРguez
October 7, 2015
1 CCF components
Name of CCF VALDATE List of Blocks
changed
CAL VERSION XSCS flag
XMM BORESIGHT 0025 2000н01н01T00:00:00 OM ANGVAR No
EMOS1 ANGVAR
EMOS2 ANGVAR
EPN ANGVAR
RGS1 ANGVAR
RGS2 ANGVAR
2 Changes
The XMMнNewton Time Variable Boresight was implemented in 2012. It is described in the release
notes XMMнCCFнRELн286 and XMMнCCFнRELн290.
The extrapolations made to derive corrections to the Euler angles based on past data imply that
new updates of these corrections may be necessary from time to time. An update was made in 2014
taking into account data obtained since 2012. It was implemented in XMM BORESIGHT 0024.CCF
(see XMMнCCFнRELн315).
We have observed a deviation in the o#sets trend with respect to the last update predictions,
particularly for the EPIC instruments. Therefore we present here a new update using the most
recent data.
As we did before, we have analyzed the astrometry o#sets derived from the pipeline PPS sources
lists for the EPIC and OM instruments adding to the previous data set the observations obtained
till August 2015. We have modeled the o#sets variation with time by means of a long term variation
1

XMMнNewton CCF Release XMMнCCFнRELн330 Page: 2
Table 1: Bestнfit parameters implemented in this CCF.
Instrument/coordinate P 1 P 2 P 3 P 4 P 5 P 6 P 7
EPIC/Y 0.65 --5.3Ѕ10 -4 1.4Ѕ10 -7 0.18Ѕ10 -12 0.18 --12.37 363.7
EPIC/Z 0.65 --1.5Ѕ10 -3 4.5Ѕ10 -7 --4.3Ѕ10 -11 1.37 1.08 363.2
OM/X --1.53 9.9Ѕ10 -4 --9.5Ѕ10 -8 0.0 --1.13 1.00 362.5
OM/Y --2.39 2.1Ѕ10 -3 --2.0Ѕ10 -7 0.0 0.84 --3.10 362.6
plus a periodic (nearly one year) oscillation (Talavera &RodrТРguezнPascual [1]).
To avoid large deviations in the extrapolation beyond August 2015, for EPIC we have used the
IDL function TS FCAST(X,P,Nval), where X are the fitted values up to August 2015 (Rev. 2878),
P=846 and N=423.
As explained in XMMнCCFнRELн290, the same o#sets obtained for EPIC can be used to process
RGS data.
# = (P 1 + P 2 Ѕ T + P 3 Ѕ T 2 ) + P 4 T 3 + P 5 Ѕ cos[2# Ѕ (T - P 6 )/P 7 )]
where # is the measured o#set and T is the time in Julian days elapsed since January 1, 2000.
The new bestнfit parameters are given in Tab.1. As before, the long term component for the EPIC
is fitted with a third order polynomial, while for OM the polynomial is of second order.
3 Scientific Impact of this Update
The release notes XMMнCCFнRELн286 and XMMнCCFнRELн290 explain in detail the improvements
in the astrometry achieved with the Time Variable Boresight.
We have made a small adjustment to compensate for the deviation observed, in particular for the
EPIC and RGS where the corrections derived using XMM BORESIGHT 0024.CCF di#ered more
than 2 arc sec in the most recent observations.
We show in Figures 1 and 2 the o#sets and the fitted corrections. The di#erences between
XMM BORESIGHT 0024.CCF and this new CCF can be seen there.
4 Estimated Scientific Quality
The quality of the corrections can be assessed by comparing the catalog o#sets obtained with the
constant and the new variable boresight. This comparison was presented in the previous release
notes, XMMнCCFнRELн286 and XMMнCCFнRELн290.

XMMнNewton CCF Release XMMнCCFнRELн330 Page: 3
DY
00 02 04 06 08 10 12 14 16
Year
н5
0
5
arcsec
DZ
00 02 04 06 08 10 12 14 16
Year
н5
0
5
arcsec
Figure 1: OM measured o#sets and fit: in blue CCF 0024, in red CCF 0025
DY
00 02 04 06 08 10 12 14 16
Year
н5
0
5
arcsec
DZ
00 02 04 06 08 10 12 14 16
Year
н5
0
5
arcsec
Figure 2: EPIC measured o#sets and fit: in blue CCF 0024, in red CCF 0025

XMMнNewton CCF Release XMMнCCFнRELн330 Page: 4
5 Test procedures
The concept of time variable boresight and its implementation were intensively tested in their first
issue. At that time more than 4000 observations obtained since the beginning of the XMMнNewton
operational life were processed with SAS using the new concept CCF.
Since this new release implements just a small increment in the variation of the Euler angles
o#sets, we have processed only a couple of recent ODFs to confirm the normal functioning of the
related SAS tasks.
6 Summary of the test results
As said before, the tests results can be seen in XMMнCCFнRELн286 and XMMнCCFнRELн290.
7 Expected updates
The fit to the long term trend observed in the measured o#sets assumes an extrapolation beyond
the available data. Therefore we shall continue monitoring the o#sets in the future to confirm the
predicted trend or to modify the fit as we have done now.
References
[1] Talavera A., RodrТРguezнPascual P., 2011, XMMнSOCнTNн0041, available at:
http://xmm2.esac.esa.int/~xmmdoc/CoCo/CCB/DOC/Attachments/INSTнTNн0041н1н0.pdf.