EAST-WEST GEO SATELLITE STATION-KEEPING WITH DEGRADED THRUSTER RESPONSE

The higher harmonic terms of Earth's gravitational potential slowly modify the nominal longitude of Geostationary Earth Orbit (GEO) satellites while the third-body presence (Moon and Sun) mainly affects its latitude. For this reason GEO satellites periodically need to perform station-keeping maneuvers, namely, East-West and North-South maneuvers to compensate for longitudinal and latitudinal variations, respectively. During the operational lifetime of GEO satellites, the thrusters-response when commanded to perform these maneuvers slowly departs from the original nominal impulsive behavior. This paper addresses the practical problem of how to perform reliable East-West station-keeping maneuvers when thruster response is degraded. The need for contingency intervention from ground based satellite operators is reduced by breaking apart the scheduled automatic station keeping maneuvers into smaller maneuvers. Orbital alignment and attitude are tracked on-board during and in between sub-maneuvers, and any off nominal variations are corrected for with subsequent maneuvers. These corrections are particularly important near the end of lifetime of GEO satellites, where thruster response farthest from nominal performance.

EAST-WEST GEO SATELLITE STATION-KEEPING WITH DEGRADED THRUSTER RESPONSE Conference Paper