Introduction to Satellite Systems

• A satellite is an artificial object which is placed intentionally into an orbit of any natural satellite. Satellites are used for many purposes i.e. weather forecasting, digital transmission, scientific research and development etc.
• In a communication context, a satellite is a specialized wireless transmitter/receiver that is launched by a rocket and placed in orbit around the earth.
• A satellite can be natural, like the moon, or artificial (human made). So we can say that a satellite is an object that moves in a curved path around a planet.

• Satellite can travel around planets or around stars such as our sun. All the planets are satellites around the sun.
• Satellites which are far away from the surface of the earth can cover a wide area on the surface of the earth.
• The moon is earth's original, natural satellite, and there are many man-made (artificial) satellites for example: SPUTNIK, ECHO, and SYNCOM.

History of Satellite Systems

There is a long history of the development of satellites system from a communications point of view. Some important events are shown below in a tabular form:

Year	Description
1945	Arthur C. Clarke publishes an essay titled "Extra Terrestrial Relays"
1957	First satellite, SPUTNIK
1960	First Reflecting communication satellite, ECHO
1963	First Geostationary satellite, SYNCOM
1965	First Commercial geostationary satellite, "Early Bird" (INTEKSAT I): 240 duplex telephone channels or 1 TV channel, 1.5 year lifetime.
1976	Three MARISAT satellites for maritime communication.
1982	First mobile satellite telephone system, INMARSAT - A
1988	First satellite system for mobile phones and data communication, INMARSAT -C
1993	First digital satellite telephone system
1998	Global satellite systems for small mobile phones.