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Special science exposures
Optimal scientific usage of the XMM instruments sometimes requires special
(science) exposures. These are not overheads and therefore part of the
requested science observing time:
- RGS spectroscopy mode data to be taken before or after high
time resolution mode observations in order to identify the
location of the incident spectrum on the CCD array (and thus
the timing of the readouts) very accurately.
- An OM image should be acquired before every grism exposure.
- OM fast mode images should be embedded in an image mode science
window. This will help with the fixed pattern noise correction,
as it provides a template at the proper count rate level.
European Space Agency - XMM Science Operations Centre