Space communications move into the millimetre-wave bands

It is pointed out that the sector of the geostationary satellite orbit serving the U.S. and Canada is already overfilled, while the European sector is not far behind. Several approaches are being considered to expand communications capacity. One of these involves a utilization of other frequencies. Less than 10 years after development was begun of satellite systems operating in the Ku band (14 or 17 GHz uplink, 11 or 12 GHz down), there is already one operational service operation in Ka band (usually 30/20 GHz). The advantages and drawbacks regarding the employment of millimeter waves are discussed, and a brief listing is presented of current or planned satellite communications projects using frequency bands verging on the Extra-High Frequency (EHF) spectrum. Attention is given to Japan's experience regarding millimetric-wave services, developments related to NASA's ACTS satellite, the European Space Agency's L-SAT, French and Italian developments, and the German communications satellite Copernicus.