SILEX: The First European Optical Communication Terminal in Orbit

T. Tolker-Nielsen & J.-C. Guillen

Optical communication is presently in a rapid expansion phase, since it offers a considerable growth potential to the constantly increasing useful transmitted data rate demand. Planned constellations of communication satellites will benefit from the use of optical communication’s ability to transmit the increasingly higher data rates with compact, low-mass terminals, while avoiding interference problems and radio frequency band saturation. In addition to semiconductor lasers and highly sensitive wide bandwidth optical communication sensors,optical communication implies utilisation of a wide range of leading-edge technologies, e.g. ultrastable structural materials, high-precision pointing mechanisms, large CCD matrices, fast digital signal processing, high precision optics, optical coatings with high reflectivity or narrow filter bandwidth and accurate thermal control.

In 1991 the development phase of an optical communication system, SILEX (Semi-Conductor Inter Satellite Link EXperiment) was started with MMS (F) as prime contractor leading a large European consortium.

The step from the optical bench in the laboratory to an optical terminal in orbit is enormous. This step was achieved when PASTEL (PASsager TELecom) on SPOT-4 was successfully launched on 22 March 1998.