Calibration of XIS data with Spaced-row Charge Injection (SCI)
Accumulated radiation damage inevitably compromises the performance of
CCD chips in-orbit. This can be mitigated by operating the CCDs with
Spaced-row Charge Injection (SCI),
which was made available to Suzaku observations starting in
the fall of 2006 and is now (since start of the AO-2 observations)
Although the improvement in spectral resolution was confirmed during
the test period, Version 1.X processing was carried out with older
versions of software and calibration files that cannot account for
the effects of SCI on XIS data. In particular, the PI values
in Version 1.X XIS files are incorrect for observations with SCI.
Version 2 processing incoroporates the calibration of SCI, so that
PI values are correct, and a keyword has been added to indicate whether
XIS was operated with or without SCI. The response generator,
xisrmfgen reads this keyword and automatically generates
appropriate RMF files. Moreover, the reduction in effective area
that accompanies improved spectral resolution can be reflected in
the ancilary response files by using xisexpmapgen (new tool)
and xissimarfgen (updated).
More details will be found in the Suzaku Memo 2007-06.