XMM RPS Users' Manual

   
Filling in OM details

For an OM exposure users must choose one of the OM optical elements , the exposure time for that optical element, exposure offset (normally 0) and one from a list of OM modes /OM default configurations . For a screenshot of an OM exposure form sheet, see Fig. 15.

  

Figure 15: Screen shot of an OM exposure form sheet for an exposure with the U filter (filter wheel position 3), in imaging mode, using the default configuration for EPIC pn as prime instrument, with 1000 s exposure time for each of the five sub-exposures comprising a default configuration exposure.

OM exposure time limits

Due to internal memory capacity and telemetry bandwidth restrictions OM science exposures have a limited range of allowed exposure times. For the default configurations (see below) these limits are:

Mode	Allowed range [s]
IMAGING mode	800-5000
FAST (1 window)	1000-4400

For non-default configuration observations exposure times within these ranges are also valid. The allowed ranges will be wider, depending on target and OM science window properties.

Choice of OM modes/configurations

Because of the complexity of OM, default configurations have been defined for its two basic science modes, i.e., the imaging mode and the fast mode (see Table 5). However, the list of OM instrument configurations does not only contain two default configuration options, but 12. This arises from the fact that there are five X-ray instruments which can be chosen as prime, and the OM itself. Because of the potentially small size of the OM science windows (in particular for fast mode observations) and the expected instrument misalignment, separate default configurations have been defined for each OM mode for each instrument as prime. The modes EPIC PN IMG (FST) are the default configurations for the modes IMAGING (and FAST), with EPIC pn as prime. IMAGE and IMAGE FAST are the default configurations for OM as prime, with either only an IMAGING mode window or a FAST mode window embedded in an IMAGING mode window. See the UHB for details on OM default configurations . An example is also displayed in § 3.3. When choosing one of the OM default configurations users do not need to specify any further details (and thus do not need to press the ``Add Details'' button, but can proceed to the next OM exposure.

The mapping of the OM mode names used in the UHB and by XRPS is described in Tab. 5.

 

Table 5: Mapping of OM mode names

UHB Name	XRPS Name1	Prime Instrument
Non-default obs.2	SCI USER DEF	Any
GO-OFF	GO-OFF3	Any
IMAGING4	EPIC MOS 1 IMG	EPIC MOS-1
FAST5	EPIC MOS 1 IMG FST	EPIC MOS-1
IMAGING4	EPIC MOS 2 IMG	EPIC MOS-2
FAST5	EPIC MOS 2 IMG FST	EPIC MOS-2
IMAGING4	EPIC pn IMG	EPIC pn
FAST5	EPIC pn IMG FST	EPIC pn
IMAGING4	RGS 1 IMG	RGS-1
FAST5	RGS 1 IMG FST	RGS-1
IMAGING4	RGS 2 IMG	RGS-2
FAST5	RGS 2 IMG FST	RGS-2
IMAGING6	IMAGE	OM
FAST7	IMAGE FAST	OM

Notes to Table 5:
1) During AO-1 only the highlighted modes are recommended for use.
2) Non-default observations are discouraged; however, see § 5.3.3.7 regarding OM grism observations.
3) Safe position to protect OM from bright sources in the field of view.
4) Default configurations (see text) have been defined to ease the use of the OM. There is one default configuration for each X-ray instrument as prime.
5) The same as for the IMAGING mode. Here, the correct choice of configuration (to match the choice of the prime instrument) is even more important than for IMAGING mode observations, because OM FAST mode windows are only about $11''\times12''$ in size (compared to a possible misalignment of up to 2').
6) IMAGING mode default configuration for OM as prime instrument.
7) FAST mode default configuration for OM as prime instrument.

XRPS will read the choice of prime instrument made by the use and will offer in the OM modes pull-down menu only those that are compatible with that prime instrument. Thus, the user will see only part of the configurations/modes from Tab. 5 listed in the pull-down menu on the screen. Reconsidering the choice of prime instrument AFTER having specified OM exposure details, one must go back and change these entries in compliance with the newly defined prime instrument. Otherwise the exposures are invalid (XRPS will flag an error condition).

SCI USER DEF is the option to choose any mode (IMAGE or FAST or a combination of both by having different windows operate in different modes) and customised window sizes without a default configuration. More details on how to fill in non-default OM observations follow in § 5.3.3.6.

Note: The OM science mode SCI USER DEF is the only way to request grism observations with the zeroth order image covered by a fast mode window, as described in § 5.3.3.7, below.

Choice of OM optical elements and the correct sequence

This has been described in § 3.2; users should follow the five steps outlined there. In § 3.2 links are provided to the relevant sections of the UHB.

OM camera unit

There is only one OM camera; the instrument unit is therefore not a user-selectable parameter.