Category Archives: Satellite Radio

Weather and climate Orbit levelLow (around 800 kilometres above Earth)How many are there? About 40The satellite recently destroyed by China was one of the thousands of disused (or “sleeping”) weather satellites in low- Earth orbit. Satellite-borne instruments have allowed researchers to track weather patterns, changes in sea levels and the amount of carbon dioxide in the atmosphere. When the Orbiting Carbon Observatory ( below) lifts off in 2008, it will be the first Nasa spacecraft designed to make precise measurements of atmospheric carbon dioxide from an Earth-orbiting satellite. Ability to track retreating polar ice, shifting patterns of drought, winds and rainfall and other environmental changes is “at great risk” because of faltering efforts to replace satellite- borne sensors. “Nasa has prioritised its missions, starting with a manned flight to Mars, then the establishing of a permanent base on the moon. Examining our own planet sadly comes last,” says F Sherwood Rowland, an atmospheric chemist at the University of California.Broadcast Orbit levelhigh (35,000 kilometres above Earth)How many are there?ThousandsIf the Earth were flat, you could pick up broadcast television thousands of miles from its source. Satellite television solves the problems of range and distortion by transmitting broadcast signals from space. Television satellites such as the one used by British Sky Broadcasting lie in geosynchronous orbit, meaning that they keep pace with the speed of the Earth. Most TV satellites are approximately 35,000 kilometres away. If you happen to have access to a yacht in the Caribbean, close to the Equator, they are easily visible and resemble small shooting stars. Satellites are increasingly used in the US to deliver radio signals. Bob Dylan did wonders for satellite radio’s profile when he took to the space airwaves with his own show last year. Data transfer