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XMM-Newton CCF Release Note
XMM-CCF-REL-126
EPIC MOS Bad Pixels
B. Altieri
December 3, 2002
1 CCF components
Name of CCF VALDATE EVALDATE List of Blocks CAL XSCS
(start of val. period) (end of validity period) changed VERSION ag
EMOS1 BADPIX 0016 2002-12-11T12:00:00 BADPIX NO
EMOS2 BADPIX 0016 2002-12-11T12:00:00 BADPIX NO
2 Changes
Completely new set of of bad pixels tables have been derived, applicable for the MOS cool operations,
that started on revolution 533. The operating CCD temperatures of both MOS were lowered from
-100C to -120C, in order i) to mitigate the eects of CTI degradation on the energy resolution and
ii) to reduce the number of bad pixels.
As anticipated and shown for the previous MOS2 cooling test in revolution 448, reducing the
CCD operating temperature was very successful in reducing hot pixels and defects such as the high-
PHA high recurrence frequency pixels, from the micrometeoroid impacts. The number of hot pixels,
determined as having a mean recurrence frequency above 1% went down from MOS1 from 98 to 38
and for MOS2 from 167 to 24, for all CCDs. And these are the one that have been agged in the
new BADPIX CCFs.
The start start validity date (VALDATE keyword) will have to be coordinated with the uplink
of the new MOS bright pixel table, as soon as possible after revolution 533.
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3 Scientic Impact of this Update
With the cool (-120C) CCD operations the new bad pixel tables are matching better than earlier
the real hot pixels.
4 Estimated Scientic Quality
There should be no more any pixels above 1% recurrence frequency.
Besides the general low-energy noise is also severly reduced, reducing further the electronic
background of the data.
One issue still need to be addressed and checked: with the CCD cooling the energy of the high-
PHA hot pixels, from the micrometeoroid impacts went down. A few that were ltered by the EDU
thresholding before have appeared and are now aged. Most of the ones present before have virtually
disappeared, but one ought to check if some valid X-ray event can be generated and detected at the
place where there was such defects before, i.e. "holes" of 3x3 pixels agged before with an "H" in
the CCF (="not-uplinked bad pixels), which are not agged as such in this new release.
5 Test procedures & results
First, the start validity date of this new CCF still has to be dened. Second, an ODF from ob-
servation acquired after revolution 533 and with the corresponding new bad pixel tables uploaded
on-board shall be used to properly test these CCF (iseu 16) in the future.
6 Expected Updates
Futher in time, as the CCD will continue degrading some more pixels shall appear, for instance in
the dramatic case of the dust micromeoroid impacts, necesitating further updates of this CCF, to
reduce TM bandwidth and raw event le sizes.