Communications satellites launched by giant rockets have been orbiting the earth since the 1960s. Aboard each satellite is a radio receiver to receive signals from the earth, an amplifier to strengthen these signals, and a transmitter to send them back to earth. All this electronic equipment is run by solar batteries, or batteries powered by the sun.
TV shows, radio programs, and telephone conversations can be transmitted from one part of the earth to another through any of the several communications satellites now in orbit. One satellite alone, INTELSAT IV, can receive and transmit 5,000 telephone conversations and 12 TV shows, all at the same time! And INTELSAT IV is less than 10 feet tall!
If, for example, the Wimbledon Tennis Championships are to be transmitted throughout the world from England, that signal is sent up from a transmitting station in England to three satellites in orbit: one, over the Atlantic Ocean; one, over the Indian Ocean; and one, over the Pacific Ocean. Both the ground stations sending and receiving the signals must point their antennas directly at the satellite for the signal to be transmitted clearly.
The first TV pictures beamed to earth from the moon were sent via satellite by the Apollo astronauts when they made their moon landing!
