Optical data links for the STAR mission

An intersatellite optical data link based on laser diodes with silicium avalanche photodiodes and a CO2 laser is described. The optical system is based on a 250 mm Cassegrain telescope with telecommunication and pointing/acquisition subassemblies for the low orbit satellite; and a 500 mm Cassegrain telescope for the geosynchronous satellite. Performance analyses indicate that for the high bit rates demanded (400 Mbits/sec) laser diodes are a feasible alternative to classical data links, if pointing accuracy of 1 micro rad can be achieved, and if a semiconductor source with 50 mW power and the required lifetime and reliability is found.