The communication technology has emerged hyperbolically giving birth to numerous advancements and sophistications studded with variety of applications. It is no longer a single straightforward system but a series of continual steps that make up a never ending process. Communication satellites play very vital role in this process. A satellite itself is composed of three separate units, namely the fuel system, telemetry control system and the transponder. The transponder being the main communication device includes; a receiving antenna to pick up signals from the ground station, a broadband receiver which encompasses audio and video channels, an input multiplexer to receive many signals at a time and a frequency converter which is used to reroute the received signals through a high powered amplifier for downlink.
The primary role of a satellite is to reflect electronic signals. In the case of a telecom satellite, the primary task is to receive signals from a ground station and send them down to another ground station located a considerable distance away from the first one. This relay action can be two-way, as in the case of a long distance phone call. Another use of the satellite is in the case television broadcasts, the ground station’s uplink is then downlinked over a wide region, so that it may be received by many different customers possessing compatible equipment. Still another use for satellites is observation, where in the satellite is equipped with cameras or various sensors, and it merely downlinks any information it picks up from its vantage point.
Communication satellites can be categorized into two major types as:
Geosynchronous Earth Orbit (GEO) satellites, their orbital speed perfectly matches with the spin of earth so they appear stationary with reference to a point on the earth.
Low Earth Orbit (LEO) satellites, their orbital speed is much faster due to low altitude so they appear moving with reference to a point on the earth for instance it can cross length or breadth of Pakistan in an hour but its successive handing offs to successor satellites can make communication process continuous. Numerous such satellites can be placed into earth orbit, and the technology being applied to the is forever growing in sophistication.