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Status report 89

		ROSAT Status Report #89
		   April 1st 1994

The ROSAT AO5 deadline was yesterday (Mar. 31, 1994).  Thank you to
everyone who submitted proposals.  If you did submit 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      rosat::duesterhaus
(301) 286-3569

=                                                                       =
=              ROSAT NEWS No. 27   ---      1-Apr-1994                  =
=                                                                       =
=                 ROSAT Scientific Data Center at the                   =
=       Max-Planck Institut fuer Extraterrestrische Physik (MPE)        =
=                 Postfach 1603, 85740 Garching, FRG                    =
=  e-mail addresses (Uli Zimmermann):                                   =
=   rosat_svc@mpe-garching.mpg.de (Internet) or                         =
=   MPE::ROSAT_SVC (SPAN)                                               =
=  ROSAT Service Area read-access via anonymous ftp:                    =
=   ftp rosat_svc.mpe-garching.mpg.de      user: anonymous              =
=   WFC Archive access via telnet/ftp ait.physik.uni-tuebingen.de       =
=                                user: xuv  (password: xuv_archive)     =

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

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

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

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 with 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 to use 
drmpspc_ao1.bdf. For observations later than Oct 11, 1991, drmpspc.bdf is 

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 Februar 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.

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, and 
has also been included in the EXSAS patch tar file (in the same 

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

   |   Best wishes for a Happy Easter from your ROSAT team at MPE   |