XMM RPS Users' Manual

   
Filling in RGS details

Similar to the EPIC exposures, a few details must be defined for each RGS exposure. Fig. 14 provides an example for an RGS exposure formsheet.

  

Figure 14: Screen shot of an RGS exposure form sheet for a 45 ks exposure of RGS-2 in the recommended mode for standrd spectroscopy.

For RGS the following inputs must be provided: exposure time, exposure offset (should normally be 0), RGS unit and RGS modes .

RGS modes

The descriptions of the RGS modes in the UHB and XRPS differ because of the changes that the modes and their names have undergone with time (see Tab. 4).

 

Table 4: Mapping of RGS mode names

UHB name	XRPS name1
SPECTROSCOPY2	SPECTROSCOPY3
SPECTROSCOPY2	SPECTR+Q4
SPECTROSCOPY2	HER5
SPECTROSCOPY2	HER+SES6
SPECTROSCOPY2	HER+SER7
HIGH TIME RESOLUTION (HTR)	HTR MULTIPLE8
HIGH TIME RESOLUTION (HTR)	HTR SINGLE CCD9

Notes to Table 4:
1) During AO-1 only the highlighted modes are recommended for use.
2) The SPECTROSCOPY mode comes in 5 different flavours (see text for details).
3) Not recommended for use, no Q calibration data transmitted with the science data.
4) Default and recommended SPECTROSCOPY mode. Q calibration data are telemetered interleaved with the science data to monitor the optical CCD loading.
5) HIGH EVENT RATE spectroscopy mode. Reduction of data rate by onboard application of an event threshold. No Q data are transmitted. Not recommended for use in AO-1.
6) HER + Single Event Reconstruction; only single pixel events are telemetered. Not recommended for use in AO-1.
7) HER + Split Event Reconstruction. Split events are reconstructed onboard before transmission to ground. Not recommended for use in AO-1.
8) Readout of all 9 CCDs.
9) Readout of only a single CCD.

The users' choice for RGS is between ``SPECTR+Q'' and ``HTR SINGLE CCD'' or ``HTR MULTIPLE''. SPECTROSCOPY without Q data (i.e., Q memory calibration data based on which the optical loading of the RGS CCDs is monitored) is not recommended, because then the optical loading of the CCD chips cannot be calibrated properly offline. Use of the other configurations of the spectroscopy mode (HER, HER+SER, HER+SES) reduces the instrument telemetry by reducing the level of detail to be transmitted per event. HER applies an onboard event threshold; onboard split event reconstruction (SER) further reduces the telemetry rate; the highest data reduction in a spectroscopy mode is reached with HER plus single event selection (SES). Use of these options is not suggested, unless there is concern that the instrument telemetry is likely to exceed the allocated limit. This should then be stated clearly in the scientific justification. When the telemetry rate is exceeded in the SPECTR+Q mode, the first alternate choice should be HER observations. The recommended modes are highlighted in Tab. 4. Note that there is an additional page which must be filled out in case special observation details are required (§ 5.3.3.4).

Exposure offset

Should be 0 again in order to avoid times during which the instrument is idle.

RGS unit

As in the case of EPIC MOS, there are also two RGS units. When first entering the RGS exposure form sheet the RGS unit is a selectable parameter. When re-entering the page again later (after successful committal of the input to memory), this parameter is fixed. Exposures must be defined for both RGS units independently. It is not possible to copy an RGS-1 exposure for use with RGS-2.