Satellite TV has been around for decades now and has become a leader in television delivery technologies. Most people know that a signal is relayed from the main distribution center up to the satellite and then bounced back to the dish on your roof in order to deliver TV to your home. However, not many people actually know how a satellite works and what is involved in creating a network of satellites that can provide coverage to an entire country, or many different countries. Here, we'll explore a bit of the behind the scenes work that occurs while delivering satellite television to your home. Up In Space By definition, a satellite is anything that orbits the Earth in a circular or elliptical path. The Moon is, by this definition, a satellite of the Earth. Also, the Earth is a satellite of the Sun. As far as modern technology is concerned, a satellite is a piece of equipment that orbits the Earth and performs a certain function. Satellites are not mass produced from a factory. Each is specifically designed to perform a certain task, and this makes for a lot of variety. Some satellites are used to track weather patterns, others are used form triangulation in the Global Positioning System (GPS), and some are used for scientific purposes. For example, the Hubble Space Telescope is a satellite affixed with an array of lenses and photography equipment that is used to take pictures of space without the atmospheric interference experienced at land-based observatories. The satellites that we are most interested in for the purposes of this articles are communications satellites. Communications Satellites Inside communications satellites are a number of important systems. For satellite TV customers, it is vital that the satellite stay in a geosynchronous orbit, meaning that it is in the same patch of sky at all times, so the satellite has guidance systems built in to maintain position. The most important piece of equipment, however, is the transponder. A transponder is a device that receives a signal at one frequency and then retransmits it at another frequency to avoid any interference with the source signal. Inside each communications satellite are thousands of transponders. The television provider's distribution center will transmit a signal directly to the satellite. The satellite's transponders will analyze that signal and then retransmit it on a different frequency. The satellite dish mounted on your roof is designed to pick up signals on that frequency and acts like an antenna. The signal then travels to the set-top receiver box, where it is decoded and you can watch your favorite programming.