Astronomical satellite payloads have nowadays reached such a high degree of complexity that often specialized software systems have to be set up and maintained by the project to enable individual observers to properly evaluate their scientific data.
In particular, this is true for the ROSAT observatory where data from survey and pointed mission phases taken with different focal plane instruments, according to a complex mission timeline, have to be dealt with.
For data evaluation support of ROSAT observers the ROSAT Scientific Data Center (RSDC) at the Max-Planck Institut für Extraterrestrische Physik (MPE) in Garching has set up a Standard Processing and Analysis System (SASS) routinely applied to all data and the Extended Scientific Analysis System (EXSAS) for individual interactive data analysis work of the ROSAT observers.
Although EXSAS has been developed specifically for data analysis of the ROSAT instruments, its structural design is sufficiently general to serve equally well also data from other X-ray and XUV instruments. EXSAS has been built on top of the well-known and widely accepted ESO-MIDAS environment and is thus available to the many astronomical sites already using MIDAS.
By construction EXSAS should be a lively and open-ended system, where applications can be easily modified and expanded according to specific needs. In this sense the EXSAS team always welcomes user supplied application software that is sufficiently general to be distributed with the system. To make EXSAS as useful as possible all EXSAS users are strongly encouraged to report us their critical comments and suggestions for future editions of the EXSAS software and documentation.
Ulrich Zimmermann
August 1991