LEO, MEO, GEO- Low, Medium, Geosynchronous Earth Orbit

LEO:

LEO: Low Earth Orbit satellites have a small area of coverage. They are positioned in an orbit approximately 3000km from the surface of the earth

 They complete one orbit every 90 minutes

 The large majority of satellites are in low earth orbit

 The Iridium system utilizes LEO satellites (780km high)

 The satellite in LEO orbit is visible to a point on the earth for a very short time

MEO:

MEO: Medium Earth Orbit satellites have orbital altitudes between 3,000 and 30,000 km.

 They are commonly used used in navigation systems such as GPS

GEO:

GEO: Geosynchronous (Geostationary) Earth Orbit satellites are positioned over the equator. The orbital altitude is around 30,000-40,000 km

There is only one geostationary orbit possible around the earth

 Lying on the earth’s equatorial plane.

 The satellite orbiting at the same speed as the rotational speed of the earth on its axis.

 They complete one orbit every 24 hours. This causes the satellite to appear stationary with respect to a point on the earth, allowing one satellite to provide continual coverage to a given area on the earth's  surface

 One GEO satellite can cover approximately 1/3 of the world’s surface

They are commonly used in communication systems

Advantages:

 Simple ground station tracking.

 Nearly constant range

 Very small frequency shift

Disadvantages:

 Transmission delay of the order of 250 msec.

 Large free space loss.

 No polar coverage

Satellite orbits in terms of the orbital height:

According to distance from earth:

 Geosynchronous Earth Orbit (GEO) ,

 Medium Earth Orbit (MEO),

 Low Earth Orbit (LEO)

GEO: 35,786 km above the earth, MEO: 8,000-20,000 km above the earth & LEO: 500- 2,000 km above the earth.