The scientific and technical aspects of the geostationary orbit

Abstract

The GSO is populated at present by less than 170 active satellites, by more than 110 non-functional objects and by an unknown number of debris. The number of radiocommunication Space Stations notified to the IFRB, in the co-ordinating process and with advance publication is 457. The simplified description of the GSO with a spherical Earth as the only attracting body is insufficient and misleading. Perturbations by the attraction of the Moon and the Sun and by other minor natural forces have to be taken into account in order to arrive at a realistic description of the orbit. Since natural forces do not admit of a geostationary satellite, man-made station-keeping is necessary to maintain the satellite at or near its nominal orbital position. The presence of non-functional objects and debris in the GSO is a source of possible danger to active satellites. The probability of a collision is small on the average but may be considerably higher at overcrowded longitudes. The probability of collision will increase in the future and will be very important for large space structures. Scientific grounds underlying sovereignty claims over segments of the GSO are discussed. International agreements on restricting the amount of non-functional objects and debris and on a systematical removal of inactive satellites into disposal orbits are indispensable for a continued use of the benefits of the GSO.