Abstract :
Evolution
of Communication Satellites
During early 1950s, both passive and active satellites were considered
for the purpose of communications over a large distance. Passive satellites though
successfully used in the early years of satellite communications, with the advancement
in technology active satellites have completely replaced the passive satellites.
Passive Satellites
The principle of communication by passive satellite is based on the properties of scattering of electromagnetic waves from different surface areas. Thus an electromagnetic wave incident on a passive satellite is scattered back towards the earth and a receiving station can receive the scattered wave. The passive satellites used in the early years of satellite communications were both artificial as well as natural.
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