XMM RPS Users' Manual

   
For a bright extended source

6.

Possible adjustment of optimal pointing position

If it is important to ensure that any particular part of the extended object does not fall on a CCD gap, users must choose the pointing direction appropriately (see UHB sections on EPIC pn chip array and EPIC MOS chip array ).

7.

Science mode of all instruments

For each of MOS and pn, it must be decided if any part of the source is bright enough to give rise to local photon pile-up that would degrade the calibration beyond the science goals when using the full frame imaging mode (see UHB section on EPIC pile-up ). In the case of a bright extended source, pile-up might be a concern. Then the user must decide whether full frame imaging with pile-up in the brightest parts should be performed or partial frame imaging on one chip to avoid pile-up, at the loss of imaging data over part of the extended object.

Even for bright sources, in particular when extended, photon pile-up should not be a problem in RGS observations. Therefore, it should in most cases be possible to leave it in the default SPECTROSCOPY mode (see UHB section on RGS modes ).

For a bright extended source the OM should be best operated in its imaging mode. It must be decided if a specific field of view coverage is needed or if the default OM sequence of 5 exposures per filter is adequate. If yes, a default configuration should be chosen (see UHB sections on OM modes and OM default configurations ).

8.

Length of observation

If the observation is long compared with the visibility window (as reported by the online XMM Target Visibility Tool), the user must consider how best to split it up, e.g., into multiple observations that fit into continuous visibility periods. Other criteria for the split of an observation could be optimal filling of gaps between CCDs, or a calculation to fit in a certain sequence of OM filters observed with one of the OM default configurations (i.e., with exposure multiples of five per filter).

9.

Selection of EPIC optical blocking filter

Users must check the visible magnitude of in-field or nearby optical targets. If the soft X-ray response is important, one should choose the thinnest filter compatible with the brightest visible objects, as described in the UHB section on EPIC filters .

10.

RGS readout sequence

For standard SPECTROSCOPY mode observations with RGS no inputs are necessary to choose a non-default CCD readout sequence. In case of particularly strong emission lines, observers might want to read out individual CCDs more often than others (see § 5.3.3.4).

11.

Choice of OM filter sequence

For the OM it must be decided if specific filter coverage is necessary for the science or if the recommended filter sequence is adequate (see UHB section on OM default configurations ).

12.

Length of exposures

While no limits are expected on the length of exposures for the X-ray instruments while observing faint sources (except for visibility constraints and the length of the observation), OM exposures are further constrained by telemetry and memory capacity limits (§ 5.3.3.5).