Bridging the World
The first experiments to bounce radio signals off large balloons in space were not very successful. They were followed in July 1962 by a satellite called Telstar. It caused a sensation by sending the first live TV pictures from America to Europe. Today, there are hundreds of communications satellites. Most of them are owned by private companies. They fly in geostationary orbits, 36 000 km above the equator, so that they can broadcast over a large area.
TV, phone and radio signals are sent up to the satellite by a large dish. They are amplified (strengthened) by the satellite, then sent to a receiving station. TV signals may also be broadcast directly to dishes on the roofs of houses.
Communications satellites are now very large and powerful. Many of them are launched by Europe's Ariane rocket. The Thaicom 4 satellite launched by Ariane-5 on 11 August 2005 weighed 6.5 tonnes. It was the largest privately-owned communications satellite ever launched.
Last update: 11 January 2011