International Mobile Satellite Organization

Stephane Gosselin

Dennis Roy Mullins

Peter Poskett

Shinichi Nomoto

Shimichi Nomoto

A method and apparatus for preventing interference between a first satellite and a second satellite which share frequencies for their up or down links is disclosed. A ground station receives downlink interference above an acceptable threshold from the first satellite if the first satellite and the second satellite are separated, relative to the ground station, by less than a minimum discrimination angle. Likewise, the first satellite receives unacceptable uplink interference from the ground station in that situation. To overcome the problem of interference, the second satellite is prevented from transmitting to or receiving from a forbidden area of the earth's surface. The forbidden area may either be determined as an area within which the first satellite and the second satellite are separated by less that the minimum discrimination angle, or as a band within which the first satellite is separated by less than the minimum discrimination angle from any point within an orbital band within which the second satellite is located. Communications to and from the forbidden area are either handed over to other areas outside the forbidden area for routing into the forbidden area through a ground network, or are handed over to another satellite.

Method and apparatus for limiting interference between satellite systems

A satellite system facilitates communications between earth stations and both geostationary satellites and non-geostationary satellites in an orbit at a lower altitude than that of said the geostationary satellites by preventing the non-geostationary satellite from transmitting signals that might possibly interfere with signals transmitted by the geostationary satellites. The non-geostationary satellite includes position acquisition subsystem for determining the position, and in particular the latitude, of the non-geostationary satellite relative to the surface of the earth. A data processor determines a forbidden band of locations on the surface of the earth all possible geostationary satellites and the non-geostationary satellite, at its determined position, are separated by less than a specified minimum discrimination angle. An antenna control subsystem in the non-geostationary satellite controls transmission of signal energy from the non-geostationary satellite in accordance with the satellites position so as to prevent transmission of signal energy from the non-geostationary satellite to said locations within the forbidden band.

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Lannion, France

Stephane Gosselin