Satellite radio, more formally known as Satellite Digital Audio Radio Service (SDARS), is a broadcasting network in which digital high-fidelity (hi-fi) audio entertainment is transmitted from orbiting satellite s to receivers on the surface. Signals can be received either directly from a satellite or indirectly by means of earth-based repeater s. Programming can also be received through Internet connections.
The first SDARS satellite was launched in the autumn of 2001 by the company now known as XM Satellite Radio. The second satellite was launched during the summer of 2002 by the company now called Sirius. These satellites transmit radio frequency (RF) signals at approximately 2.3 gigahertz (GHz). Satellite radio provides programming on a subscription basis. Users pay a nominal monthly fee for the service and in turn receive programming that contains almost no advertising. The programming consists mainly of music but also includes news, weather, sports and traffic information. The services are used primarily by motorists although receivers can be installed in residences and businesses. Portable receivers also exist.