Satellite Systems can be classified based upon their orbits as low earth orbit, medium earth orbit & geostationary earth orbit systems. Geostationary is also the highest earth orbit and hence, also provides the greatest visibility using only a few satellites. The coverage region of a satellite is called its footprint. This is the region from which the satellite is visible. Three geostationary satellite footprints ensure complete coverage of the earth as shown:

geostationary

Hence, there is permanent or 24 hour visibility of geostationary satellites without the need of handoffs. While LEO & MEO satellites do not have 24 hour visibility as the satellites have smaller footprints since they are closer to the earth (low satellite height). Hence, a larger number of satellites are needed to cover the earth. Also, since each satellite has a small footprint, handoffs are also required between satellites.

Major differences between LEO, MEO & GEO satellite systems:

Parameter LEO MEO GEO
Satellite Height 500-1500 km 5000-12000 km 35,800 km
Orbital Period 10-40 minutes 2-8 hours 24 hours
Number of Satellites 40-80 8-20 3
Satellite Life Short Long Long
Number of Handoffs High Low Least(none)
Gateway Cost Very Expensive Expensive Cheap
Propagation Loss Least High Highest

Note -

  • HEO refers to highly elliptical orbits which have a visibility of about 12 hours.
  • ICO or intermediate circular orbit is an example of MEO.
  • GPS satellites are not in Geostationary orbits but instead, they orbit twice for every rotation of the earth at a height of 20, 000 km.
  • Handheld terminals have low sending power are hence use LEO for mobile communication. LEO are also closest to the earth, have better signal strength and less time delay.

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