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XMMíNewton CCF Release Note
XMMíCCFíRELí315
Astrometry: time variable boresight update
A. Talavera and P. RodrÒÐguez
July 28, 2014
1 CCF components
Name of CCF VALDATE List of Blocks
changed
CAL VERSION XSCS flag
XMM BORESIGHT 0024 2000í01í01T00:00:00 OM ANGVAR No
EMOS1 ANGVAR
EMOS2 ANGVAR
EPN ANGVAR
RGS1 ANGVAR
RGS2 ANGVAR
2 Changes
The XMMíNewton Time Variable Boresight was implemented in 2012. It is described in the release
notes XMMíCCFíRELí286 and XMMíCCFíRELí290.
After two years of successful use of the Time Variable Boresigh, it has been decided to update
the o#sets to be applied to the Euler angles as a function of time.
We have analyzed the astrometry o#sets derived from the pipeline PPS sources lists for the EPIC
and OM instruments using all data obtained by XMMíNewton and processed with the standard
pipeline. This analysis shows a slight deviation in the more recent o#sets with respect to the trend
predicted in the current fit, contained in XMM BORESIGHT 0023.CCF.
As we did before we have modeled the o#sets variation with time by means of a long term
variation plus a periodic (nearly one year) oscillation (Talavera & RodrÒÐguezíPascual [1])
As explained in XMMíCCFíRELí290, the same o#sets obtained for EPIC can be used to process
1

XMMíNewton CCF Release XMMíCCFíRELí315 Page: 2
Table 1: Bestífit parameters implemented in this CCF.
Instrument/coordinate P 1 P 2 P 3 P 4 P 5 P 6 P 7
EPIC/Y 0.64 --5.2½10 -4 1.4½10 -7 --9.2½10 -12 0.16 --20.2 365.6
EPIC/Z 0.91 --2.1½10 -3 7.8½10 -7 --8.9½10 -11 1.40 2.23 363.0
OM/X --1.51 9.8½10 -4 --9.2½10 -8 0.0 --1.16 4.07 361.9
OM/Y --2.43 2.2½10 -3 --2.4½10 -7 0.0 0.85 --2.99 362.6
RGS data.
# = (P 1 + P 2 ½ T + P 3 ½ T 2 ) + P 4 T 3 + P 5 ½ cos[2# ½ (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 bestífit parameters are given in Tab.1. Note that the long term component for the EPIC
is fitted now with a third order polynomial, while for OM the polynomial remains of second order.
3 Scientific Impact of this Update
The release notes XMMíCCFíRELí286 and XMMíCCFíRELí290 explain in detail the improvements
in the astrometry achieved with the Time Variable Boresight.
Now we have made a small adjustment to compensate for the deviation observed in the measured
o#sets with respect to the predicted trend. This deviation is very small for OM, less than 0.5 arc sec
in both Euler angles in the most recent observations, as it is shown in Fig. 1 However for the EPIC
and RGS the deviation is larger, of the order of 1í2 arc sec in the # Euler angle (Z coordinate),
reaching 3 arc sec by 2016. (See Fig.2)
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, XMMíCCFíRELí286 and XMMíCCFíRELí290.
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 XMMíNewton

XMMíNewton CCF Release XMMíCCFíRELí315 Page: 3
DY
00 02 04 06 08 10 12 14 16
Year
í5
0
5
arcsec
DZ
00 02 04 06 08 10 12 14 16
Year
í5
0
5
arcsec
Figure 1: OM measured o#sets and fit: in blue CCF 0023, in red CCF 0024
DY
00 02 04 06 08 10 12 14 16
Year
í5
0
5
arcsec
DZ
00 02 04 06 08 10 12 14 16
Year
í5
0
5
arcsec
Figure 2: EPIC measured o#sets and fit: in blue CCF 0023, in red CCF 0024

XMMíNewton CCF Release XMMíCCFíRELí315 Page: 4
operational life were processed with SAS using the new concept CCF.
Since this new release implements just a small increment in 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 XMMíCCFíRELí286 and XMMíCCFíRELí290.
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 need to continue monitoring the o#sets in the future to confirm
the trend or to modify the fit as we have done now.
References
[1] Talavera A., RodrÒÐguezíPascual P., 2011, XMMíSOCíTNí0041, available at:
http://xmm2.esac.esa.int/~xmmdoc/CoCo/CCB/DOC/Attachments/INSTíTNí0041í1í0.pdf.