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| A satellite in an elliptical geosynchronous orbit will appear to oscillate in the sky from the viewpoint of a ground station, and satellites in highly elliptical orbits must be tracked by steerable ]s. | A satellite in an elliptical geosynchronous orbit will appear to oscillate in the sky from the viewpoint of a ground station, and satellites in highly elliptical orbits must be tracked by steerable ]s. | ||
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| ==Active geosynchronous orbits== | ==Active geosynchronous orbits== | ||
Revision as of 17:52, 30 April 2004
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A geosynchronous orbit is an orbit that has the same rotational period and direction as the rotation of the Earth.
A circular geosynchronous orbit in the plane of the Earth's equator has a radius of approximately 42,164 km (from the center of the Earth), and an object placed there would find itself in a height of approximately 35,790 km (22,240 statute miles) above mean sea level.
This can be demonstrated analytically by application of the Law of Gravity and the physics of centripetal acceleration. Drawing the free body diagram and using the analysis methods of engineering dynamics and Physics allows the determination of the distance from Earth's center of mass which will satisfy this specified operating condition.
Circular geosynchronous orbits
An ideal circular orbit that kept the satellite over a single point on the Earth's equator at all times is called a geostationary orbit.
In general, a perfect stable geostationary orbit is an ideal that can only be approximated. In practice, several different practical methods of station keeping allow satellites to remain over a required region of the Earth's surface.
The name "Clarke Belt" has been given to the part of space approximately 35,790 km directly above Earth's equator where near-geostationary orbits may be achieved. Science fiction writer and scientist Arthur C. Clarke wrote about this belt in 1945, hence the name. Clarke's and Herman Potočnik's visions of geostationary communications satellites were made a reality in 1962 with the launch of Telstar.
Elliptical geosynchronous orbits
Elliptical orbits can be and are designed for communications satellites that keep the satellite within view of its assigned ground stations or receivers.
A satellite in an elliptical geosynchronous orbit will appear to oscillate in the sky from the viewpoint of a ground station, and satellites in highly elliptical orbits must be tracked by steerable ground stations.
Active geosynchronous orbits
Theoretically Statites can use active thrust to balance a portion of the gravity forces experienced. Thus it can be "geo synchronous" in an orbit different from the traditional definition established in the early era of initial space exploration activities.
History
The first communications satellite placed in a geosynchronous orbit was Syncom 2, launched in 1963. Geosynchronous orbits have been in common use ever since.