Max-Planck-Institut für extraterrestrische Physik
8.2 System Design
Deutsche Version MPE HEG X-Ray Astronomy Wave ROSAT
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8.2 System Design
The architectural design of SASS was guided by the demand that the overall system should be highly portable and easily maintainable over a time span of two decades.
SASS was developed in FORTRAN 77 and was initially running on VAX computers under the DEC VMS operating system. Keeping up with the rapid development in computer hardware SASS meanwhile runs on DEC ALPHA workstations. The relational database management system INGRES was choosen to steer, control, and log the automatic processing. A set of rules describes and regulates the input/output data flow and interfaces between the main S/W components, i.e., the steering system, PSPC and HRI S/W packages.
The steering system mainly consists of an elaborate configuration management to control the data flow, the version of the processing parameters and programs, and the interface to the mission planning. It provides the interface to the archiving system and to the off-line analysis levelII S/W packages like EXSAS [Zimmermann et al.1992, Zimmermann et al.1993] and PROS\ [Worrall et al.1992].
The SASS S/W packages in total comprise almost one million lines of code, parts of them are still subject to continuous update. SASS is able to process and reprocess the actual incoming data in parallel. A diagram of the interface components of SASS is shown in Fig. 8.1.
Figure 8.1:
Diagram showing the interfaces of the various components
of the standard analysis software system (SASS).
The processing of the data is done in a pipeline of four major steps:
- the SAV processing checks and saves incoming data,
- the TEL processing handles raw time-ordered telemetry data on a day-by-day basis,
- the OBI processing handles the observation intervals, into which an observation request has been split by GSOC, as fields on the sky,
- the SEQ processing merges observation intervals, detects sources, and determines source properties.
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