Sirio 1 (Satellite Italiano ricerca industriale orientato) was primarily a
geostationary communications satellite. It included experiments measuring the local plasma
and field environment and the flux of low-energy cosmic rays.
The satellite was launched on a Delta-2313
and was located at 15 deg w longitude.
The Sirio-2 geostationary spacecraft carried two independent payloads:
- an S-band multichannel transponder for meteorological data dissemination ('MDD') in
Africa, and
- an laser detection/time-tag/retroreflector assembly to permit atomic clock
synchronization over intercontinental distances (laser synchronization from stationary
orbit - 'LASSO').
The cylindrically shaped spacecraft measured 144 cm in diameter and 240 cm in length
including the apogee boost motor. The primary structural members are equipment platforms
and a central thrust cone carrying conventional housekeeping electronics in addition to
payloads. Attitude, orbit and spin rate control were performed using a hydrazine
propulsion system including four thrusters. The spin rate would have been maintained at 90
rpm throughout the two-year nominal lifetime. A mechanically despun antenna relayed S-band
telemetry (meteorological and housekeeping), while a traditional omnidirectional turnstile
system supported VHF ranging and telecommands, as well as housekeeping telemetry in
transfer orbit and as backup geostationary orbit.
Sirio-2 was lost in a Ariane-1 launch failure
in 1982.
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