Sirio-2 assembly at ESTEC

Sirio-2 was to be positioned in geostationary orbit over Africa, to relay meteorological data between centres on that continent using simple receive/transmit stations. The other payload was Laser Synchronisation from Stationary Orbit (Lasso), designed for synchronising high-precision clocks at widely-separated locations at low cost. Lasso consisted of 98 laser reflectors (the panel can be seen here on Sirio's conical launch adapter), photodetectors for sensing laser pulses, and an ultrastable oscillator/counter to time-tag the pulse arrivals. Different ground stations could thus observe the reflected pulses and use the time-tagging to compare their clocks. Unfortunately, Sirio-2 was lost in the Ariane launch failure of 10 September 1982, along with ESA's Marecs maritime telecommunications satellite. [Image Date: 1982] [82.02.002-009]