Basic Principles

A satellite is a body that moves around another body in a mathematically predictable path called an Orbit. A communication satellite is nothing but a microwave repeater station in space that is helpful in telecommunications, radio, and television along with internet applications.

A repeater is a circuit which increases the strength of the signal it receives and retransmits it. But here this repeater works as a transponder, which changes the frequency band of the transmitted signal, from the received one.

The frequency with which the signal is sent into the space is called Uplink frequency, while the frequency with which it is sent by the transponder is Downlink frequency.

The following figure illustrates this concept clearly.

Now, let us have a look at the advantages, disadvantages and applications of satellite communications.

Satellite Communication − Advantages

There are many Advantages of satellite communications such as −

Ø  Flexibility

Ø  Ease in installing new circuits

Ø  Distances are easily covered and cost doesn’t matter

Ø  Broadcasting possibilities

Ø  Each and every corner of earth is covered

Ø  User can control the network

Satellite Communication − Disadvantages

Satellite communication has the following drawbacks −

The initial costs such as segment and launch costs are too high.

v  Congestion of frequencies

v  Interference and propagation

  Satellite Communication − Applications

Satellite communication finds its applications in the following areas −

v  In Radio broadcasting.

v  In TV broadcasting such as DTH.

v  In Internet applications such as providing Internet connection for data transfer, GPS applications, Internet surfing, etc.

v  For voice communications.

v  For research and development sector, in many areas.

v  In military applications and navigations.

The orientation of the satellite in its orbit depends upon the three laws called as Kepler’s laws.

Kepler’s Laws

Johannes Kepler (1571-1630) the astronomical scientist, gave 3 revolutionary laws, regarding the motion of satellites. The path followed by a satellite around its primary (the earth) is an ellipse. Ellipse has two foci - F1 and F2, the earth being one of them.

If the distance from the center of the object to a point on its elliptical path is considered, then the farthest point of an ellipse from the center is called as apogee and the shortest point of an ellipse from the center is called as perigee.