What is satellite? Where the satellites can be placed?

What is satellite?

                             Any object revolving in space is said to be satellite.Natural satellites are moon,planets etc.Artificial satellite is man made object send to space to revolve in orbit.But here we use the term satellites instead of artificial satellites.Satellite is the only object by which we can transmit and receive information at any distance.

Where the satellites can be placed?

                                 Satellite can be allowed to revolve either at low earth orbit or medium earth orbit or at Geostationary orbit.These orbits are classified because of the presence of Van Allen Belts.Satellites cannot be placed in these Van Allen Belts because they are hazardous to satellites.They are formed by torous of energetic particles. 

VAN ALLEN BELT: 

                                There are two Doughnut shaped Van Allen Belts above the earth surface.They are (1)Upper Van Allen Belt and (2)Lower Van Allen Belt.

                                Van Allen Belt is named after its discoverer James Van Allen.These Belts seperate Low Earth Orbit(LEO),Medium Earth Orbit(MEO),and Geostationary Earth Orbit(GEO).Satellites revolving in these orbits are said to be LEO satellites,MEO satellites and Geostationary Earth Orbit satellites respectively.The Van Allen radiation Belts are formed due to earth's magnetic field by high energy particles like protons and electrons .

EARTH ORBITS

 
LOW EARTH ORBIT:

                              Low Earth Orbit is the lower most orbit. Satellites at an altitude of approximatly 160-2000km is said to be LEO satellites.Since Low Earth Orbit is closer to earth only less amplification is required for transmission of signals to satellites and the round-trip delay is only in the range of a few milliseconds(10-30 ms) .Some of the examples of LEO satellites are Iridium(780km & 66 satellites),Globalstar(1400 km & 48 satellites), etc

 MEDIUM EARTH ORBIT:

                                Medium Earth Orbit is located in between two Van Allen Belts. MEO satellites are satellites at an altitude of approximately 18,000km and above. These Satellites  perform Navigation process. Some of the examples of MEO satellites are GPS (GLOBAL POSITIONING SYSTEM),GLONASS,GALILEO etc.

GEOSTATIONARY EARTH ORBIT:

                                Geostationary Earth Orbit is located above the upper Van Allen Belt. Satellites at an altitude of 35,800km in a circular equatorial orbit would seems motionless in the sky.Such satellites are said to be Geostationary Earth Orbit satellites.Some examples of GEO satellites are GOES O,GOES P etc..

Author

Arul shiju.S.V