Overview and Origins

Data from the ROSAT XRT is processed by the SASS (Scientific Analysis Software System) before being converted to a FITS format and then distributed to the PI. This processing occurs at MPE for data belonging to German and UK PIs, and at GSFC for US PIs. Both the SASS and the FITS conversion software have evolved throughout the mission, but more fundamentally, the FITS conversion up until May 1994 was different at MPE from that at GSFC. (This corresponds to SASS versions earlier than 7_1.) Data distributed after that date was FITS converted using yet another form of the FITS standard, `Rationalized Data Format' (RDF). This FITS conversion is now common between MPE and GSFC.

Starting at around the same time as the FITS software change, a re-processing of all data using the evolved SASS was started. This has become known as the `Rev 2 re-processing'. The output from this re-processing are RDF files. Data in the Leicester public archives currently consist of a mix of RDF and pre-RDF FITS files. As of Feb 2000 around 3 percent of the old datasets remain. It is, however, anticipated that the database will be completely RDF within a matter of months.

ASTERIX 2.3-0 reads RDF FITS files directly. Earlier ASTERIX versions converted all FITS format files to HDS files using the program xrtconv. xrtconv has been withdraw in version 2.3-0.