EXSAS is designed to work with preprocessed data sets where, by the standard processing in the RSDC, different calibrations and normalizations have already been applied to the raw data. To guarantee system independence data are distributed in FITS format. A ROSAT data set, containing the data from a specific observation, is uniquely defined by its sequence number, a 6 digit number. It contains all data from the observation plus additional auxiliary information usually needed for detailed data evaluation as well as selected results of the Standard Analysis Processing of that data.
All XRT data processed since early 1994 are delivered in the so-called RDF (Rationalized Data Format). The appropriate command to input such data into the MIDAS/EXSAS environment is INTAPE/RDF. Before the project changed to RDF, data were delivered in two other data structures: the German ROD structure (designed for MIDAS/EXSAS) and the US PROS [Worrall et al.1992] compatible structure (designed for the US IRAF/PROS package). Data in these older structures (still in the archives) have to be input using the commands INTAPE/ROD and INTAPE/USROD, respectively. All three commands can read data from either disk or cassette/tape and allow several options for treating the input according to the needs of the user.
WFC data as delivered from the German WFC Data Center (GXUVDC at AIT) should be input by the command INTAPE/ROD.
Observers serviced by the German data centers will receive data from their observations on either a DAT (DDS) cassette (preferred medium) or on an Exabyte cassette (in exceptional cases delivery on normal magnetic tape (9-track, 6250/1600 bpi) is still possible) automatically as soon as data have passed the Standard Processing. As long as data rights are connected with a specific observation, usually for one year after the data have been delivered to the Principal Investigator of the observation, these data cannot be requested by anybody else from the archives. Afterwards these data are available via network access from the ROSAT Archive.