A satellite is any object that orbit another object. Satellites can be spacecraft manufactured on Earth and sent into orbit on a launch vehicle, they may be naturally occurring such as moons, comets, stars, planets, and even galaxies.
Satellite television is television delivered by way of communications satellites as compared to conventional terrestrial TV and cable TV. In many areas of the world satellite television services supplement older terrestrial signals, providing a wider range of channels and services, including subscription-only services.
The first satellite television signal was relayed from Europe to the Telstar Satellite over North America in 1962. Satellite television, like other communications relayed by satellite, starts with a transmitting antenna located at an uplink facility. Uplink satellite dishes are very large, as much as 9 to 12 meters (30 to 40 feet) in diameter. The increased diameter results in more accurate aiming and increased signal strength at the satellite. The uplink dish is pointed toward a specific satellite and the uplinked signals are transmitted within a specific frequency range, so as to be received by one of the transponders tuned to that frequency range aboard that satellite. The transponder 'retransmits' the signals back to Earth but at a different frequency band (to avoid interference with the uplink signal), typically in the C-Band(4–8 GHz) and/or Ku-Band(12–18 GHz). The leg of the signal path from the satellite to the receiving Earth station is called the downlink. |
