Natural Satellite (Moon)
What is a satellite?
Ans:-It is an object that moves around the orbit of a planet or star. For example, Earth is a satellite because it orbits the sun. Likewise, The moon is a satellite because orbits Earth. It is of two types one is natural satellite and another is artificial satellite. For example, Moon is the natural satellite of earth where as sputnik I and Bhaskara I and II are the artificial satellite of earth.
Artificial Satellite
What is communication Satellite?
Ans:- A communication satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder and creating a communication channel between a source transmitter and a receiver at different locations on Earth.


Receiving antenna
Satellite are an essential part of telecommunications systems worldwide today. They can carry a large amount of data in addition to TV signals. When the data is transmitted using satellite then it is said to be satellite communication.
Satellite communication is a special use of microwave transmission system. A satellite is placed precisely at 36000 Km above the equator where it's orbit speed exactly matches the earth's rotation speed. Hence it always stays over the same point with respect to the earth. This allows the ground station to aim it's antenna at a fixed point in the sky.
Diagram
The ground station consists of a satellite dish that functions as an anteena and communication equipment to transmit (Called Up-link) and receive (Called Down link) data from satellites passing overhead. Such satellite can caused $ 60 millions to build but only three of them are needed to cover the entire earth's surface. Capacity of number of channels used in satellite communications depends on the frequency used. Typical data transfer rates are 1 to 10 Mb/s.
Satellites are especially used for remote locations, which are difficult to reach with wired infrastructure. Also communications and data transfer on internet, is only possible through satellites.
Advantages of Satellite communication

  1. It covers a vast range of area.
  2. The wire communications is almost impossible and too costly to use across continents, where the satellite communications proves to be the best alternative.
  3. it is very useful in very long distance television distribution.
  4. Earth stations, Which receives the signals can be fixed position or relatively mobile.

Disadvantages of satellite communication

  1. It is very costly. So, It is not use for persona or low budget communication.
  2. There is atmospheric loss of transmitted signals.
  3. Due to low antenna signals, band width over crowded.