Abstract: A wireless communication system includes a satellite constellation consisting of a plurality of satellites. Each of the plurality of satellites is in an orbit whose eccentricity and inclination are perturbed relative to the same geosynchronous orbit. Each of the satellites in the constellation is capable of relaying signals in either direction between a central ground hub and a plurality of mobile user terminals. The plurality of satellites are configured such that the period of their geosynchronous orbit remains substantially constant at one sidereal day.

Abstract: A fault detection system for a satellite communication system includes a satellite positioned above earth. Satellite has a payload that communicates with a network control center on earth. System ground stations generate diagnostic messages and transmits the diagnostic messages to the payload. Each diagnostic message has a predetermined path characteristic so that the diagnostic message takes a predetermined path through the payload, or part of the payload, if the payload is operating properly. Parts of the payload, if any, which do not permit deterministic path tracing using externally applied diagnostic messages may be probed by using internal signal or data injection points. In response to the externally applied or internally injected diagnostic message, a response signal is generated at the payload. The response signal is transmitted to the network control center where it is compared with a predetermined response.