Small laser terminal for operational intersatellite links

Applications for line-of-sight communications links between spacecraft include data relay from LEO spacecraft, telecommunications between satellites in GSO or LEO orbits, secure communications in military satellite constellations, and links to manned spacecraft. Optical technology will be the preferred choice for many such applications due to potential advantages of small antenna (telescope) size and low mass and power. MMS has been leading the development of the technologies needed for such terminals under the ESA funded SILEX 1 programme and two flight models are now under integration. In parallel, a second generation terminal known as the Small Optical User Terminal (SOUT) has been developed to elegant breadboard level under ESA funding. The advantages of low mass and power can now be realised due to recent advances in semiconductor laser technology. MMS has combined its experience in SILEX and SOUT to produce a concept for a small terminal which will be attractive to users in the nearterm. This retains essential features of the SOUT such as the softmount interface, combined acquisition and tracking sensor, and fibre coupled lasers. It also minimizes cost by re-using SILEX derived electronics and other space qualified elements. The terminal has a 7 cm diameter telescope, a mass below 50 kg, and will provide a 50 Mbps data link with SILEX. The main features of the terminal are presented in this paper together with the chief applications which are envisaged.