A communication satellite is an artificial satellite that acts as a large repeater in the sky. It receives signals from the source transmitter, amplifies using transponders, and relays them to the receiver. Thus, it creates a communication channel between locations of the earth that would not have been able to communicate due to long distance or obstruction by earth’s curvature.
Communication satellites may be owned by government or private organizations. Presently, there are more than 2000 communication satellites in the sky. Some of its uses are −
Communication satellites are broadly categorized into three types depending upon the orbit in which they are placed.
Geostationary Satellite (GEO) − They are at 36,000 km from the earth’s surface. They have same orbital period as earth’s rotation. So they appear to be still in the sky. At least 3 GEOs are needed for global coverage.
Medium Earth Orbit Satellite (MEO) − They are placed between the two Van Allen belts, at a distance between 2,000 km to 36,000 km from the earth’s surface. At least 10 MEOs are needed for global coverage.
Low Earth Orbit Satellite (LEO) − They are situated below the Lower Van Allen belt. Their orbital altitude is 160 km to 2000 km. For global coverage, as high as 50 LEOs are required.