SIRIO-2 - Conception and present status

The design, objectives and present status of the SIRIO-2 geostationary spin-stabilized satellite to be launched in early 1982 from Kourou, French Guyana are presented. SIRIO-2, the basic design of which was derived from that of its predecessor, SIRIO-1, carries a payload consisting of two experiments: the Meteorological Data Distribution (MOD) experiment, intended to connect African and Asian meteorological stations, and the Laser Synchronization from Synchronous Orbit (LASSO) experiment, for clock synchronization over intercontinental distances with an accuracy of about 1 nsec. Differences in the configurations of SIRIO-1 and 2 are related to the dimensions of the MDD despun S-band antenna, different spin directions and the interface of the spacecraft with the Ariane launcher with the SYLDA double launch system. Development tests have been performed on a mechanical model, an integration model and a flight model employing existing hardware wherever possible, and are currently at the stage of acceptance testing of the flight model, to be followed by mechanical testing, thermal vacuum tests, a leak check, an operational spin test and repeat electrical and physical tests. Delivery to ESA is planned for the middle of November, 1981.