The SASS

The Standard Analysis Software System converts the ROSAT telemetry into scientifically useful files. It performs standard scientific operations on these files, and generates postscript output summarising the observation. The data in the files that make up a ROSAT XRT observation dataset have all been through the SASS, however, the SASS does not make the FITS files that PIs and archive users receive, this is done by later software.

The SASS was written by MPE and SAO. Identical copies run at MPE and GSFC, although it has been continuously updated throughout the mission. A brief description of the SASS follows, however, the details of what specific versions of the SASS have done have proved difficult to uncover. What is clear is that later versions of the SASS produce significantly more reliable results than earlier versions. Confidence has risen to the point that with SASS version 7_1 the entire set of observations to date are being re-processed (the so-called `Rev 2 re-processing').

The following modules make up the SASS.

SAV - copies telemetry tape to disk, deleting duplicate records, and separates PSPC from HRI data.

TEL - splits data into continuous observing intervals and identifies these with the timeline, assigns quality flags to detector and aspect data.

OBI - applies the aspect solution and screens out bad data. Determines components of background map.

SEQ (PSPC) - merges observation, makes images, performs source detection and identification, makes spectra and light curves and applies statistical tests to these.

SEQ (HRI) - as above, but no spectra or scientific light curves made.