Laser links two satellites

November 30, 2001 marked the first-ever transmission of an image by laser link from one satellite to another. Terminals on the European Space Agency's (ESA) Artemis spacecraft, operating 19,270 miles above Earth, and the French space agency's (CNES) SPOT 4 satellite, orbiting at 517 miles altitude, exchanged high-definition imagery data at 50 megabits per second. Images from SPOT 4 via Artemis were subsequently transmitted to the SPOT Image control center in Toulouse, France. Effective cooperation between several operations control centers ensured success. These included the CNES SPOT 4 control center and the SPOT Image data reception/processing facility in Toulouse, the ESA-Artemis mission control facility in Redu, Belgium, and the Artemis operations control center in Fucino, Italy. The main advantage offered by the optical data relay system is enhanced availability. When operated with SPOT 4, the link can be maintained for more than 50% of the orbit. This increases contact time dramatically and shortens the time interval between when images are recorded and when they are available to the customer. System potential also extends beyond Earth observation, promising to revolutionize satellite-to-satellite communications for constellations in low-earth orbit, geo-stationary satellites, and deep-space exploration probes. Contact Bernard Cabrieres at CNES for more information. Tel: +33 5 61 27 42 47, or [email protected].