XMM-Newton Phase II RPS Users Manual

3.1.2.1 For a faint extended source

7.

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 XMM-Newton Users Handbook sections on EPIC pn chip array , EPIC MOS chip array and position angle constraints ).

8.

Science mode of all instruments

For both MOS and pn, when using the ''Full Frame'' imaging mode, it must be decided if any given part of the source is bright enough to give rise to local photon pile-up that would degrade the calibration beyond that demanded by the science goals (see XMM-Newton Users Handbook section on EPIC pile-up ). If not, the ''Full Frame'' mode should be used.

RGS data of faint extended sources are compromised by low total count numbers and a reduced energy resolution. RGS should be used in the normal ''Spectroscopy'' mode (see XMM-Newton Users Handbook section on RGS modes ).

For a source that is faint and very extended also in the optical, the OM should be best operated in its ''Full Frame Low Resolution'' mode (see more about OM modes in § 5.2.4.5).

9.

Observation duration

If the observation is long compared to the visibility window (as reported by the online XMM-Newton Target Visibility Tool), the user must consider how best to split the observation, e.g., into multiple observations that fit into continuous visibility periods.

10.

Selection of EPIC optical blocking filters

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 XMM-Newton Users Handbook section on EPIC filters .

11.

RGS readout sequence

For standard ''Spectroscopy'' mode observations with RGS, a standard readout sequence is proposed which can be modified according to the needs of the user (see XMM-Newton Users Handbook section 3.4.5 on RGS modes ).

12.

Choice of OM filter sequence

For OM, it must be decided if a specific filter coverage is necessary for the science, or if the recommended filter sequence is adequate (see XMM-Newton Users Handbook section on OM modes and OM optical elements ).

13.

Exposure duration

While no limits are expected on the exposure duration for the X-ray instruments observing faint sources (except for visibility constraints and the duration of the observation), OM exposures are further constrained by telemetry and memory capacity limits (§ 5.2.4.5).