SATELLITE COMMUNICATION

Satellite communication is the mode of communicating a signal between a transmitter and a receiver by relaying it through an artificial satellite. A message signal originating at an Earth (ground) station is transmitted up to an on-board satellite via an uplink, typically operating in a frequency band around 6 GHz; the satellite's transponder receives and amplifies this signal, and then retransmits it back down to a different Earth station via a downlink, typically operating around 4 GHz. This scheme exists because high-frequency line-of-sight radio signals, travelling in a straight line, can be blocked by tall buildings, mountains, or simply by the curvature of the Earth itself over long distances -- problems a communication satellite, sitting far above the Earth in geostationary orbit, sidesteps entirely by relaying and amplifying the signal to reach distant, otherwise unreachable ground stations, which is why a communication satellite is often described as a radio repeater in the sky. Satellites are built and classified for different jobs: weather satellites monitor the Earth's weather and climate, using measurements such as cloud mass to help predict rain and dangerous storms including hurricanes and cyclones; communication satellites are used to relay television, radio and internet sign …