Software Design of the XMM Science Operations Centre

Nestor Peccia

ESA/ESOC

Abstract:
The X-Ray Multi-Mirror Mission (XMM) is a high throughput X-ray 
spectroscopy mission (phonton energy range from 01. Kev to 10 Kev), 
which is the second cornestone of the ESA long term scientific plan. 
The XMM is a facility type observatory open to the worldwide 
astronomical community, which will offer a major step forward in the 
field of X.ray astrophisics in the 21st Century. It es envisaged as a 
long duration facility class mission aimed at performing detailed 
imaging spectrophotometry on a wide veriety of X-ray sources. The 
observatory will be placed in a 48 hour highly eccentric inclined 
orbit to allow uninterrupted observations up to 41 hours using the 
groundstation of Redu (Belgien). The scientific instruments are:

- EPIC  European Photon Imaging Camera
- RGS   Reflection Grating Spectrometer
- OM   Optical Monitor

The XMM spacecraft will be operated in a continuous interactive mode 
from a Mission Operations Centre (MOC), located at Darmstadt, 
Germany. Science operations will be conducted from a Science 
Operations Centre (SOC), located at Villafranca, Madrid, Spain.

This paper describes the experience of applying ESA's procedures and 
strict system development standards to the analysis and design of the 
XMM SOC. It will be described the software design principles, the 
functional concept, its interfaces, its major subsystems and its 
hardware architecture. The SOC subsystems are as follows:

The Proposal handling Subsystem        (PHS)
The Sequence Generation Subsystem   (SGS)

The Payload Calibration Subsystem     (PCS)

The Payload Monitoring Subsystem     (PMS)

The Observation Data Subsystem         (ODS)

The Instrument Software Subsystem     (ISS)

The Archive Management Subsystem    (AMS)

The Interactive Analysis Subsystem      (IAS)

The Pipeline Processing Subsystem       (PPS)

The whole development has suscribed to the Object-Oriented approach 
under Unix environment on client-server architecture. However some of 
its subsystems (e. g. IAS, PPS and PCS) will use the traditional 
approach in order to take advantage of existing software (mainly 
science software packages) developed in support of previous 
international missions. OO and the traditional approach will coexist 
in the SOC.

At the time of presentation (September 96) the XMM SOC Software 
Requirements Phase will be at its final stage.

Additionally this paper will address how the CCSDS (Consultative 
Committee for Space Data Systems) standards are used for packaging 
the data in FITS format. The aim is to provide self-documenting data 
to the investigators at the science data centres and home institutes.

As the subsystems of any SOC / Data Centre / Archive combination are 
the same, although they may have different weight and might be 
handled by different entities, this paper will also outline how the 
XMM SOC software will be developed in order to be used by future ESA 
missions (Integral, Rosetta, First).

Keyword:   X-Ray, SOC design and implementation, OO approach