Satellite equipment

The satellite communication is the communication system primarily characterized by its global broadcasting function enabling a large amount of information to be simultaneously transmitted to many users. Both the cable communication and the wireless communication of ground-based station have not such function. A digital satellite communication system typically employs a ground-based transmitter that beams an uplink signal to a satellite positioned in a geosynchronous orbit. In turn, the satellite relays the signal back to various ground-based receivers. A satellite may receive a signal representing audio, video or data information from a transmitter. The satellite amplifies and broadcasts this signal to a receiver via a communication channel at a specified frequency and bandwidth. Satellite communication systems have emerged as a viable solution for supporting broadband services. The direct broadcast system (DBS) satellites are used to transmit television and digital audio signals to service subscribers at stationary ground sites. Direct broadcast satellite systems allow households to receive digital television, audio, data, and video directly from a geosynchronous satellite. Each household subscribing to the system receives the digital broadcast signals on a satellite dish. In addition to a satellite or satellites, a satellite communication system comprises a base station and a fixed station. The satellite network system provides the capability for mobile earth terminals to access one or more multiple beam satellites located in geostationary orbit for the purposes of providing mobile communications services. The global positioning system (GPS) is a constellation of satellites that transmits navigation information via radio signals. Receivers that are able to receive and process these radio signals may calculate position and time. GPS receivers detect and decode signals from a number of satellites orbiting the Earth. The signals from each of these satellites indicate the position of the satellite and the time at which the signals were sent. A typical GPS terminal unit includes a GPS receiver which receives the satellite signals, resident memory in which cartographic data and other location information may be stored, a processor and associated GPS software for determining the location of the unit, and a display for displaying the information along with an indication of the unit's location. The global positioning system has enjoyed increased attention being utilized in a variety of different applications requiring precise measurement of location on the surface of the earth. Some of the different applications which make use of the GPS data include: location measuring, navigation, tracking, mapping, and timing applications.