Page 20 - SATELLITE AND RADAR COMMUNICATION SYSTEM

Geostationary Earth Orbit (GEO)

 Satellites in geostationary orbit (GEO) circle Earth above the equator from west
to east following Earth’s rotation – taking about 24 hours by travelling at exactly
the same rate as Earth.
 This makes satellites in GEO appear to be ‘stationary’ over a fixed position. In
order to perfectly match Earth’s rotation, the speed of GEO satellites should be

about 3 km per second at an altitude of 35 786 km. This is much farther from
Earth’s surface compared to many satellites.
 GEO is used by satellites that need to stay constantly above one particular place
over Earth, such as telecommunication satellites. This way, an antenna on Earth
can be fixed to always stay pointed towards that satellite without moving

Advantages of GEO:
A GEO satellite’s distance from earth
gives it a large coverage area, almost a
fourth of the earth’s surface.
GEO satellites have a 24 hour view of a
particular area.

GEO is ideal for satellite broadcast and
other multi-point applications.

Disadvantages of GEO:
A GEO satellite’s distance also cause it to
have both a comparatively weak signal
and a time delay in the signal, which is
bad for point to point communication.

GEO satellites, centred above the
equator, have difficulty broadcasting sig- Figure 1.9: Geostationary Earth Orbit
nals to near polar regions.
It is require sophisticated and heavy pro-
pulsion devices on board to keep them
in a fixed orbit.

Applications: Telecommunication satellites, Weather monitoring satellites

12

Introduction to Satellite Communication System