Reliability and flexibility of the IRAS on-board software

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Reliability and flexibility of the IRAS on-board software

Hameetman, G.J.

To enhance mission reliability and operational flexibility the Infra Red Astronomical Satellite IRAS is equipped with an on-board computersystem. The software of this system takes care of vital functions like attitude control, out-of-limits checking, ground dialogue and execution of the observation programs. This paper describes the design criteria which were used during the development of the IRAS on-board software to reach the goal for this software; to create a correct software system that combines both realiability and flexibility. It further presents the results of this approach during the first five months of the mission. It can be concluded that the goals are reached. The mission is very successful, although part of the software had to be rewritten. This was necessary to save the mission when one of the attitute sensors appeared to fail. Apart from this major modification, some on-board software changes were made due to changes of operational requirements.