Satellite Communication(acs)

•  A Satellite is a celestial body which orbit around some heavenly body. 
• Communication satellites are man made satellites which forms the star point of communication is a microwave repeater in the sky that consists of diverse combination of one or more receivers, transmitters, amplifiers and many other electronic components that orbit the earth. 
• Satellites are of two types of satellites are Passive Satellites and Active satellites. Passive satellites are satellites which reflect or bounce the signals from one place or another place in earth. 
• Thus passive satellites are relay stations in space Moon is a passive satellite. A passive satellite can be further subdivided into two types, namely Natural satellites and artificial satellites.
•  A moon is a natural satellite of earth. 
• But spherical balloon with metal coated plastic serve as artificial satellites.
•  Active satellites are complicated structures having processing equipment called Transponder which is very vital for functioning of the satellite. 
• These transponders serve dual purpose i.e. provides amplification of the incoming signal and performs the frequency translation of the incoming signal to avoid interference between the two signals.
•  In a satellite communications system, two or more stations on or near the earth communicate via one or more satellites that serve as relay stations in space. 
• The antenna systems on or near the earth are referred to as earth stations. 
• A transmission from an earth station to the satellite is referred to as up link, whereas transmissions from the satellite to the earth station are down link. 
• The component in the satellite that takes an up link signal and converts it to a down link signal is called a transponder.