XMM-Newton Users Handbook

4.5.3 Special science exposures

Optimal scientific usage of the XMM-Newton instruments sometimes requires special (science) exposures. These are not overheads and therefore part of the requested science observing time:

• An OM image with an optical filter may be convenient before using the grisms.

• It is convenient and highly recommended that OM fast mode windows are 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.

Consequently, the observer should specify such additional exposures in the proposal.