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XMM­Newton CCF Release Note
XMM­CCF­REL­329
EPIC MOS Fixed O#set Tables
M.J.S. Smith
August 24, 2015
1 CCF Components
Name of CCF VALDATE EVALDATE Blocks XSCS
Changed Flag
EMOS1 DARKFRAME 0036.CCF 2015­08­12T14:50:00 OFFSET CCD1 NO
OFFSET CCD2
OFFSET CCD4
OFFSET CCD5
OFFSET CCD7
EMOS2 DARKFRAME 0032.CCF 2015­08­12T14:50:00 OFFSET CCD1 NO
2 Changes
Several columns in MOS1 peripheral CCDs, in particular CCD2, are producing a large number of
noise events. These columns probably sustained damage in the 11 December 2012 impact event.
The main objective of the latest MOS fixed o#set tables is to suppress this noise through a suitable
modification of the respective column o#sets.
As additional objective, the new o#set tables also address the canonical drift in background by
lowering the column o#sets for MOS1 SW and MOS2 LW modes by 1 ADU.
This set of CCFs reflect these modifications to the uploaded MOS fixed o#set tables, which were
implemented as of revolution 2871.
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XMM­Newton CCF Release XMM­CCF­REL­329 Page: 2
3 Scientific Impact and Estimated Quality
Note that the values in the OFFSET extensions of the DARKFRAME CCFs are not used to deter­
mine the E1 event energies; this is already done on board in the EDU. The main reason for reflecting
the on board o#set values in the DARKFRAME CCFs is correctly to determine the reconstructed
event energies, for which knowledge of the contemporary on board o#sets is required.
4 Expected Updates
As the e#ects of the CCD damage evolve, other MOS1 o#set values may require modification.
Additionally, the background of all CCDs changes in time and will need to be compensated
through periodic changes of the fixed o#sets.
5 Test Procedures and Results
Correct functionality tested with cifbuild and emproc (SAS version 14.0.0). Reducing data with
mismatched uploaded fixed o#sets and DARKFRAME CCF issue may result in SAS warnings
** emevents: (spGatti11), reconstructed energy larger than 4095 [...].
As expected, use of the CCFs in this release result in correct reconstructed energies and no such
warnings are issued.