Hobbies And Interests
Identification
A geosynchronous satellite is one that occupies a geosynchronous orbit. In this kind of orbit, the orbital period of the satellite matches the Earth's rotation. This means that from the point of view of an observer on the ground, a satellite of this kind returns to exactly the same place at exactly the same time everyday.
Misconceptions
Geosynchronous is not the same thing as geostationary. A geostationary orbit is a form of geosynchronous orbit that causes the satellite to appear to be hovering over the same location of the Earth. In common use, the term geosynchronous is often used as a synonym for geostationary, but in reality they are describe two different orbits. In a geostationary orbit, the orbit is always over the equator, always at 22,236 miles from the Earth's surface, and always matching the Earth's rotational period. A geosynchronous orbit only has one of those three requirements.
Function
Elliptical geosynchronous orbits are used for certain communications satellites to keep them in direct view (and therefore contact) with their assigned ground transmitter-receivers. These types of orbits have an advantage of not requiring the ground station to be in a position to communicate with an equatorial orbit, which is important for satellite used at very low or very high latitudes.
Geostationary orbits allow for stable, constant communication between a ground station and a satellite but are limited by the necessity for an equatorial orbit.
Considerations
No practical satellite orbit, either geosynchronous or geostationary, is perfectly stable. In reality, maintenance of such orbits requires regular adjustments, which is why satellites are often equipped with thrusters. These adjustments are called "station-keeping."
Geography
The necessity for geostationary orbits to occupy a ring of space above the equator, all at a particular altitude, plus the necessity of maintaining safe distances between satellites, places an absolute limit on the number of geostationary satellites that can be working at any one time. This has led to some dispute about control over this orbital space, with certain countries on the equator asserting that they own the orbital space above them. In theory, these disputes are supposed to be resolved at the International Telecommunications Union, but in practice they are ongoing and limited solely because the small number of countries that have the ability to launch satellites into orbit are all in general agreement over the use of geostationary orbital space.