WorldSpace began satellite audio services in 1999 and is currently broadcasting throughout Asia, Europe, the Middle East and Africa.
WorldSpace is a privately owned company that originally owned XM Satellite Radio in America and is responsible for some proprietary technology and original programming and format structure.
Sirius Satellite Radio is based out of New York City and was initially called CD Radio. The official launch date for Sirius was July 1, 2002.
XM Satellite Radio is based out of Washington, DC and was once called American Mobile Radio. The official launch date for XM was September 25, 2001.
Car manufacturers started installing satellite radio receivers in some 2001 and 2002 models. Electronics companies began launching several models of portable satellite radio receivers soon thereafter. Today, most new cars are coming equipped with satellite radio recivers.
XM uses two satellites (named "Rock" and "Roll") that are placed in parallel geostationary orbit -- one at 85 degrees west longitude and the other at 115 degrees west longitude.
Sirius uses three satellites to form an inclined elliptical satellite constellation, ensuring that each satellite spends about 16 hours a day over the continental U.S., with at least one satellite over the country at all times.
"Sirius" is the brightest star in the constellation Canis Major and the Northern Hemisphere. It was named after the ancient Egyptian god Osirus, who was represented pictographically as a dog, giving Sirius its more familiar name: "the Dog Star".
Both XM and Sirius cover much of North America, but they are licensed now for only the U.S.
There's a four-second delay due to the nature of broadcasting from satellites.
Satellite radio broadcasts are not subject to the same FCC rules as regular radio broadcasts are.
Both XM and Sirius use a network of land repeaters (usually cell phone towers) to enhance reception in urban locations and/or locations with tall buildings.
By the fall of 2004, you'll be able to buy a car navigation system that color-codes the roads according to the speed of the traffic, using real-time traffic data from XM satellites.
Sources:
http://xmradio.com/
http://sirius.com/
http://www.strathlachlan.com/blog/2003/10/satellite_radio.html
http://www.howstuffworks.com/satellite-radio.htm
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