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XMM­Newton CCF Release Note
XMM­CCF­REL­86
EPIC MOS ASTROMETRY
B. Altieri
August 2, 2001
1 CCF components
Name of CCF VALDATE List of Blocks
changed
CAL VERSION XSCS flag
EMOS1 LINCOORD 0016 2000­01­01T00:00:00 FOV NO
EMOS2 LINCOORD 0016 2000­01­01T00:00:00 FOV NO
2 Changes
The relatove positions between CCDs for both MOS cameras have been adjusted to provide the
highest astrometric accuracy over the full field­of­view of the MOS cameras. The new relative
positions are mostly derived from a study by M. Denby using the bright stellar OMC field (from rev
237), cross­correlating XMM positions with optical positions.
This has been confirmed independently by B. Altieri with deep surveys: (i) on the Lockman
Hole and cross­corralating with optical ROSAT sources counterparts, as found by Lehmann et al.
(2001) and (ii) the 100ks deep exposure on the HDF­North (revolution 271), cross­correlating with
high­accuracy VLA radio­positions from Richards et al. (2000)
A few CCDs were shifted up to 3 arcsec, mostly MOS1 CCD3 and MOS2 CCD4 and CCD5
(that cover a similar area of the sky !) The following shifts have been introduced with respect to
the previous version (15):
1

XMM­Newton CCF Release XMM­CCF­REL­86 Page: 2
MOS1 Delta CCX (mm) Delta CCY (mm)
CCD1 None None
CCD2 ­0.045 ­0.073
CCD3 0.102 0.034
CCD4 0.051 0.034
CCD5 0.010 ­0.032
CCD6 None None
CCD7 ­0.016 0.006
MOS2 Delta CCX (mm) Delta CCY (mm)
CCD1 None None
CCD2 0.035 0.062
CCD3 0.030 ­0.015
CCD4 ­0.041 0.091
CCD5 0.036 0.124
CCD6 0.006 0.099
CCD7 ­0.017 0.021
Note the plate scale is approx 1'' to 0.040 mm
There was not enough data and statistics to define the position and an eventual shift of the
CCD6 of MOS1.
3 Scientific Impact of this Update
Compared to version 15 this LINCOORD CCF will (correctly) move the coordinates of sources in
some MOS peripherical CCDs up to 3''.
4 Estimated Scientific Quality
With this CCF version the astrometric accuracy throughout the whole MOS field­of­view is believed
to be better than 1 arcsec, once a possible global shift, up to 4 arcsec (but often much less), is applied
using a cross­correlation with optical catalogue (e.g. USNO A2.0 catalogue). The Relative Pointing
Accuracy is limited by the accuracy of attitude reconstruction of the Star Tracker.
Note however that faint sources close to the detection limit have 90% coordinates confidence
radii of only 2­4 arcsec, limited by the statistical accuracy of the measurement (see Watson M.G. et
al., 2000, A&A 365, L51)
No residuals in rotation have been observed with the current BORESIGHT CCF, within the
accuracy of the current measurements.

XMM­Newton CCF Release XMM­CCF­REL­86 Page: 3
5 Expected Updates
With growing experience on other fields if some residuals are still left, the CCF might still be tuned.
The accuracy of these metrology CCFs will monitored on the NGC2516 open­cluster stellar field. For
the moment no distorsion or shift trend has been observed since the start of the mission, therefore
this CCF is applicable since the start of the mission.
6 Acknowledgements
I thank M. Denby for the useful comments on the EPIC camera metrology and his valuable work
on the OMC field.