the underlying point. The space occupied by GEOSAT-s has been described as a "three dimensional corridor" in which satellites move at different alti- tudes, speeds and inclinations to the plane of the equator. While this corridor has its obvious limitations with respect to its physical size, the major concern has been the prevention of electromagnetic interference with other satellites and other users of the radio spectrum. The minimum separating distance required between GEOSAT-s may vary depending on the type of criteria used for arriving at a determination. These criteria include the size of the satellite, the stability of the orbit, the degree of tolerated electromagnetic interference, the state of technology, and other factors. This may explain the wide disparaties in the estimates of the maximum number of satellites (ranging from 180 to 1800) . . . that could occupy the geostationary orbit at a given time. As a recent U.N. study put it: "It is impossible to state how many satellites can be accomodated in the geostationary orbit. It is, however, possible to find out if a specific satellite system, with all physical parameters defined would interfere with other systems or not"$ In 1977 there were 9 satellites placed in geostationary orbit and the total number in orbit reached about 100 in that year. It has been estimated that between 1980 and 1991 there will be 274 geostationary satellites launched and that there will be 239 active satellites m geostationary orbit during 1990. Whatever the eventual increase will be—which is expected to
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