ROSAT Status Report #89:

April 1st 1994

ROSAT Status Update for AO5

The ROSAT AO5 deadline was yesterday (Mar. 31, 1994). Thank you to everyone who submitted proposals. If you did submit a proposal(s), you should have received an e-mail receipt for the electronic copy that you submitted. If you have NOT received a receipt, please call or send me e-mail immediately.

Thank you,

Margo Duesterhaus

Proposal Manager

duesterhaus@rosat.gsfc.nasa.gov or rosat::duesterhaus

(301) 286-3569

ROSAT NEWS from MPE (No. 27; 1-Apr-1994)

SATELLITE STATUS

The satellite has performed quite stable throughout the whole month. Observation efficiency was near to 40 percent.

MISSION PLANNING

The deadline for ROSAT AO-5 proposals was March 31, 1994.

CALIBRATION

Here is an answer to some frequently occurring questions about the usage of the different PSPC detector response matrices and effective area tables:

The effective areas valid for detectors PSPC C and PSPC B differ. They can be found in the EXSAS calibration area under the filenames exsas_cal:effarea_pspcc.tbl and exsas_cal:effarea_pspcb.tbl. If you are not sure which detector was used for your observation, check the observation date (or spacecraft clock, descriptor :OBS_CLOCK). The switch from PSPC C to PSPC B took place on Jan 25, 1991 (Julian date 2448282.0, spacecraft clock SCC=20530000).
The detector response for detectors PSPC C and PSPC B is regarded as being identical. Consequently there are no separate DRM (detector response matrix) files for the two PSPCs in the EXSAS calibration area.
The spectral response of the PSPC has changed in a non-linear way with time. At the present status of calibration it is suggested to use - depending on the date of observation - one of the two following DRM's:
- exsas_cal:drmpspc_ao1.bdf (identical to exsas_cal:drmpspc_06.bdf)
- exsas_cal:drmpspc.bdf (identical with exsas_cal:drmpspc_36_300_1_full.bdf)
A convenient break point between usage of the matrices is Oct 11, 1991, (Julian date 2448541.0, spacecraft clock SCC=42910000) when a major gain change took place. For observations prior to this date (survey, calibration phase, AO-1 and the first weeks of AO-2) it is suggested that one use drmpspc_ao1.bdf. For observations later than Oct 11, 1991, drmpspc.bdf is recommended.
A major effort for a better understanding of the time-dependent non-linear gain changes of the PSPC is undertaken right now. A first round of additional PSPC ground calibrations in the PANTER facility has been completed in March, using the PSPC instrument model. A further set of ground calibrations will be started soon. In addition a variety of different in-orbit measurements from different types of sources is used to better establish the time-dependent gain dependence, in particular through the PSPC "end-of-life" calibrations currently obtained.
To summarize all this:
```
                                          recommended       recommended 
      date             SCC         PSPC   effective area    DRM           
 < Jan 25, 1991     < 20530000     C      effarea_pspcc     drmpspc_ao1       

   Jan 25, 1991       20530000     B      effarea_pspcb     drmpspc_ao1  
 - Oct 11, 1991     - 42910000    

 > Oct 11, 1991     > 42910000     B      effarea_pspcb     drmpspc       
```
In EXSAS patches after February 28, the commands FIT/SPECTRUM and BIN/DETECTOR_RESPONSE select by default the correct response matrices and effective area tables if not specified explicitly different on the command line. The decision is based on the descriptor OBS_CLOCK(1) (i.e. start SCC) of the corresponding spectral file.

EXSAS/MIDAS

A serious bug has been found in the EXSAS command INTAPE/USROD, which is used to convert US ROSAT data from PROS format (i.e. from the FITS files distributed by GSFC) into EXSAS/MIDAS format.

Only in the case of HRI photon event lists - due to an accidental change of sign after the initial tests - the photon X sky coordinate was flipped around the center of the field of view (so that East was to the right side of the image, and West to the left). If not recognized, the error could have lead to wrong coordinates for the X-ray sources in the field. The error was present both in the JAN93 and the JAN94 versions of EXSAS.

The bug fix is located in the ROSAT service area (anonymous ftp rosat_svc.mpe-garching.mpg.de) in the file exsas/patch/intaqp.prg. The fix also has been included in the EXSAS patch tar file (in the same directory).

In order to fix old HRI photon lists created by INTAPE/USROD, just use the MIDAS command: COMPUTE/TABLE events :XPIX = -:XPIX

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