SATELLITE PARTS
- Communication satellites involve the transmission of info from a ground station to a satellite in space. Then there is a retransmission of info from the satellite back down to the downlink. The satellites need to be equipped with a receiver and an antenna, or a transmitter antenna. The antennas are used to connect the uplink to the downlink for retransmission.
- The amount of power which a satellite transmitter needs to send out depends a great deal on whether it is in low earth orbit or in geosynchronous orbit. This is a result of the fact that the geosynchronous satellite is at an altitude of 22,300 miles, while the low earth satellite is only a few hundred miles. The geosynchronous satellite is nearly 100 times as far away as the low earth satellite.
- One of the biggest differences between a low earth satellite and a geosynchronous satellite is in their antennas. As mentioned earlier, the geosynchronous satellite would require nearly 10,000 times more transmitter power, if all other components were the same. An antenna used by a commercial terrestrial radio station, for example, is trying to reach people to the north, south, east, and west. However, the commercial station will use an antenna that radiates very little power straight up or straight down.
- You might wonder why we don't actually use transmitters with thousands of watts of power, like your favorite radio station does. You might also have figured out the answer already. There simply isn't that much power available on the spacecraft. There is no line from the power company to the satellite. The satellite must generate all of its own power. For a communications satellite, that power usually is generated by large solar panels covered with solars cells.