This paper addresses the problem of designing a small satellite constellation suitable for communications in Antarctica. This study has been motivated by the increasing international interests in having permanent bases in Antarctica to perform experiments in physics, atmospheric sciences, geology, and biology to name a few key areas. The existing and planned scientific expeditions in Antarctica require continuous and reliable communication services, especially during emergencies. Geostationary Earth orbit satellites do not cover this high latitude adequately, and constellations using circular orbits would require too many satellites to provide continuous regional coverage, thus increasing cost prohibitively. A three-satellite constellation using elliptical orbits is proposed to address this issue. The critical inclination has been selected to predominantly keep the satellites over Antarctica, where the satellites will dwell most of the time. This configuration has been obtained by using the two-dimensional lattice flower constellation design theory: a minimum parameter design methodology that enforces all three satellites in the same trajectory as seen from the Earth rotating frame. This aspect provides the continuous coverage necessary for reliable communications using only a small number of satellites.
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 their 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 the lifetime of GEO satellites, where thruster response is farthest from nominal performance.
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