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satellite communication systems, geostationary, low orbit satellite and GPS
What are the 4 types of satellites?
Satellites: Types of Orbit
Low Earth Orbit (LEO)
Geosynchronous Earth Orbit (GEO)
Medium Earth Orbit (MEO)
Elliptical.
A satellite is any object that orbits something else, as, for example, the Earth orbits the sun. There are hundreds of satellites in operation. They are used for diverse purposes such as weather forecasting, television signal, amateur radio and internet communications and the Global Positioning System. They are also used to look outward at the solar system for research and data gathering purposes.
In a communications context, a satellite is a specialized wireless receiver/transmitter that is launched by a rocket and placed in orbit around the Earth.
Geostationary orbit
A geostationary satellite orbits the Earth over the equator, approximately 22,000 miles up. At that altitude, one complete trip around the Earth relative to the sun takes 24 hours. These satellites remain over the same spot on the Earth's surface at all times. A geostationary satellite stays fixed in the sky from any point on the Earth's surface from which it can be seen. Weather satellites are usually of this type.
A geostationary satellite can "see" approximately 40% of the Earth's surface. Three such satellites, spaced at equal intervals -- 120 angular degrees apart -- can provide coverage of the entire inhabited world. A dish antenna aimed at the spot in the sky where the satellite is can access a satellite internet connection.
Low Earth orbit
A low Earth orbit (LEO) satellite system uses a large fleet of satellites, each in a circular orbit at a constant altitude of a few hundred miles. The orbits take the satellites over, or nearly over, the geographic poles. Each revolution takes from 90 minutes to a few hours. The fleet is arranged in such a way that at least one satellite is on a line of sight from any point on the Earth's surface at any time.
The entire system operates in a manner similar to the way a cellular telephone functions. The main difference is that the transponders, or wireless receiver/transmitters, are moving rather than fixed, and are in space rather than on the Earth. A well-designed LEO system makes it possible for anyone to have a wireless internet connection from any point on the planet, using an antenna no more sophisticated than old-fashioned television "rabbit ears."
Polar orbit
Satellites in polar orbits are the third type. Their orbits traverse the north and south poles rather than align to the equator. With a geosynchronous or elliptical orbit, these satellites can view all or most of the Earth's surface, the same as equatorial satellites. They are valuable for government and military applications.
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