Orbit attainment and maintenance for the Geosat Follow-On (GFO) satellite

Geosat Follow-On (GFO) was launched on February 10, 1998. GFO's operational orbit is the Geosat Exact Repeat Orbit, which was first used by the Geosat satellite in the 1980s. This orbit requires very precise control of the mean orbit elements and satellite groundtrack. The GFO injection orbit was significantly higher than the operational orbit. The operational orbit was attained using the I-lb thrusters of the on-board propulsion system to perform a series of 13 maneuvers of decreasing magnitude. The maneuvers were sized and timed to efficiently fly onto the operational orbit. Since attaining the operational orbit, ten drag make-up maneuvers have been performed to maintain the orbit elements within bounds. The magnitude of these maneuvers has ranged from a few mm/sec to a few tens of mm/sec. The frequency of the maintenance maneuvers averages about one per month. Both the magnitude and frequency of the maintenance maneuvers is expected to increase with solar activity. The procedures and software used to maintain the orbit have been modified based on experience.