Most of the communication today from Satellite TV Channels to GPS and Inter Country Communication to GPS runs on Satellites. Satellites are man made devices that revolve around the earth’s orbit for specific purposes. Satellites have made our life a whole lot easier. The main reason for this is that satellites do cover a huge geographical section of earth and this is the reason why a single satellite employed in earth’s orbit can serve a lot of users at the same time.
Satellites move in round orbits. A satellite’s orbit can not be elliptical around the earth. There are three types of satellites around the earth’s orbit according to the distance from earth.
The types are LEO (Lower Earth Orbit), MEO (Medium Earth Orbit) and GEO (Geo Stationary Earth Orbit). In Lower Earth Orbit, the satellite moves at 315 to 350 kilo meters above the earth’s orbit. In LEO, 45 satellites are required to cover the complete earth’s orbit. At any given point, 3 or 4 satellites are accessible from any point on earth.
In MEO, a satellite is around 19,000 kilometers around earth’s orbit. The examples of medium earth orbit satellites are weather satellites that record the Earth’s atmospheric changes and send them to earth.
The most important are Geo Stationary Earth Orbits, also known as GEO Satellites. These satellites revolve around the earth in complete synchronization with the earth’s movement around itself.
GEO Satellites are exactly 35,786 kilometers around the earth’s orbit. These satellites revolve exactly at the same speed as our earth and seem stationary in their orbit. Due to their height from earth, they seem like at the same position and do not deviate from their path. Satellite channels are transmitted from GEO satellites. 3 – 4 GEO Satellites can cover the complete earth’s crust and cover a huge geographical area.
Satellites play a key role in communication around the earth. The most essential part of earth centric satellites is their power system. All the satellites have huge wings which contain solar cells. The satellites use the sun’s solar energy to power them and perform every day routine activities. Satellites have two frequencies. One is uplink and the other is downlink. Satellite takes the uplink in the form of a beam pointing towards it and it spreads the rays downwards with a downlink frequency. In the middle time, it modulates and demodulates the frequency spectrum and performs specific functions on the data.
The other important part of the satellite is propulsion sub system. Propulsion subsystem is responsible to keep the satellite in its orbit. Whenever the satellite deviates from its original orbit, the rocket fuel in the Satellite’s Propulsion subsystem propels the rocket to come in the correct orbit. This is the reason, why satellites have an average life of 8 – 10 years because the amount of rocket fuel isn’t too much to support for ever.