Other Geosynchronous Orbits
Elliptical geosynchronous orbits can be and are designed for communications satellites in order to keep the satellite within view of its assigned ground stations or receivers. A satellite in an elliptical geosynchronous orbit appears to oscillate in the sky from the viewpoint of a ground station, tracing an analemma in the sky. Satellites in highly elliptical orbits must be tracked by steerable ground stations.
The Infrared Space Observatory was in a highly-elliptical geosynchronous orbit with an orbital height of apogee 70,600 km and perigee 1,000 km. It was controlled by two ground stations.
An active geosynchronous orbit is a hypothetical orbit that could be maintained if forces other than gravity were also used, such as a solar sail. Such a statite could be geosynchronous in an orbit different (higher, lower, more or less elliptical, or some other path) from the conic section orbit dictated by the laws of gravity.
A further form of geosynchronous orbit is proposed for the theoretical space elevator, in which one end of the structure is tethered to the ground, maintaining a longer orbital period than by gravity alone if under tension.
Other related orbit types are:
- Supersynchronous orbit – a disposal / storage orbit above GSO/GEO. Satellites drift in a westerly direction.
- Subsynchronous orbit – a drift orbit close to but below GSO/GEO. Used for satellites undergoing station changes in an eastern direction.
- Graveyard orbit – a supersynchronous orbit where spacecraft are intentionally placed at the end of their operational life.
Read more about this topic: Geosynchronous Orbit
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