In orbit storage for back-up satellites

The basic idea developed in this paper is the placement of a satellite in a storage orbit waiting for subsequent utilization instead of actuating the normal launch procedure that aims at an immediate starting of the satellite operational life. The latter case is the traditional one and it is more convenient provided that the operational life of the satellite is planned well in advance and that launch failures or delays do not cause severe damages to the mission objectves. The recend history of the launches demonstrates that to meet the start of a mission operational phase may be critical and very costly. Therefore the utilization of storage orbits may become convenient for those missions that have an obliged or optimal start phase. Storage orbits which maintain their inclination almost constant for long periods are investigated. A geosynchronous constellation of relay satellites has been addressed. This is, in fact, a typical case where the replacement of a satellite for completion of its operational life or for an unexpected failure implies critical time constraints. The results demonstrate that the adoption of such orbits is rewarding in terms of fuel consumption independently from the start-of-service date.