Abstract: A communication system includes a set of non-geostationary satellites setting up communication links between ground stations and terminals, the links from a station terminating at associated terminals in a limited geographical area including the station. A communication link between a particular station and the associated terminals is set up by a satellite of the set of satellites. The satellite is commanded to set up for this purpose a steerable transmit beam and a steerable receive beam pointing at the limited area including the particular station and supporting the communication link.

Abstract: A telecommunications system antenna for communicating, in transmission and in reception, with a large area whose position relative to the antenna varies. The antenna has motors (80, 82) for pointing the antenna towards the area and radiating elements (74, 76) associated with a control device for modifying the antenna's radiation pattern according to the relative position of the antenna and the area. When the antenna is installed on a telecommunications satellite, as the antenna moves, the antenna can remain constantly in communication with an area of the Earth covering several hundred kilometers.

Abstract: The invention concerns a telecommunications system in which the Earth is divided into areas (26) within which communications are effected by means of transmit and receive means on a spacecraft, such as a satellite, allocated to communication for a plurality of areas. Areas (2610, 2611, 2612) of a first category (28) are allocated signals having respective polarizations (PD, PG) and carrier frequencies (&Dgr;F1, &Dgr;F2) such that two adjacent areas of the first category are allocated signals having different polarizations or carrier frequencies. Each area of a second category (30) is allocated signals having all the available polarizations and all the available carrier frequencies.

Abstract: A communication system comprising a set of non-geostationary satellites provides communication links between ground stations and terminals, a communication link from a particular station via a satellite terminating at associated terminals in a limited geographical area including the station and providing a communication channel to at least some of the associated terminals. The communication link is switched to another satellite during the process of communication link handover. A communication link between a particular station and its associated terminals includes an additional communication channel which enables advance data to be transmitted between the particular station and a terminal before the latter executes a communication link handover. This data masks any interruption of communication caused by the communication link handover.