Engineers once scattered 350 million copper needles in orbit to bounce radio signals
Before satellites could reliably amplify signals, engineers tried simply reflecting them off something up high. The Moon served as one mirror. Another experiment, Project West Ford, released 350 million tiny copper needles into orbit in 1963 to form an artificial reflecting belt. Only about half spread out properly, yet messages still got through.
Radio waves used for long-distance links travel in straight lines, so the curve of the Earth blocks them. A communications satellite solves that by catching a signal and passing it on to a distant receiver, carrying television, telephone calls, radio and internet traffic. In October 1945 Arthur C. Clarke laid out the basics in an article for the British magazine Wireless World, describing satellites parked in geostationary orbit, and that orbit is still sometimes called the Clarke Belt.
The earliest relays were passive: they reflected signals without boosting them, so only a sliver of the energy reached the ground. A United States Navy project called Communication Moon Relay bounced messages off the Moon, linking Washington, D.C., and Hawaii on 23 January 1956. NASA's Echo 1, launched on 12 August 1960, was an aluminium-coated balloon that did the same job from orbit. West Ford, run by the Lincoln Laboratory at the Massachusetts Institute of Technology, was a further variation on the idea.
Active satellites, which amplify before resending, soon took over. Project SCORE, launched on 18 December 1958, carried a tape recorder and broadcast a Christmas greeting from President Dwight D. Eisenhower before its batteries died after eight hours of operation. Telstar, whose 10 July 1962 launch was the first ever paid for by a private sponsor, carried the first television pictures across the Atlantic. Syncom 3 in 1964 became the first satellite to hang fixed in the sky, and Intelsat 1, nicknamed Early Bird, followed in 1965 as the first commercial one in that kind of orbit.
A geostationary satellite sits about 35,785 kilometres above the equator, circling once a day so it seems frozen in place and ground dishes can stay pointed at it. Most communications satellites today, however, fly in low orbits in large groups called constellations, which means antennas on the ground must track them and keep switching between them.
Source: Communications satellite
