Satellite is an artificial body orbiting the earth or another planet. The first satellite, Sputnik 1, was launched by the Soviet Union on October 4, 1957. A natural satellite is a moon. There are more than 100 active satellites in orbit around the earth at altitudes ranging from a few hundred to several thousand miles. Satellites are used for communications, navigation, weather forecasting and other purposes.
The word “satellite” derives from the Latin satēllītes, meaning “attendant”. The term “satellite” originally referred to celestial bodies orbiting the sun such as planets and their moons. In 1947 German rocket scientist Hermann Oberth coined the term “artificial satellite” to describe man-made objects intended to orbit the earth. Early examples of artificial satellites were V-2 rockets carrying television cameras that transmitted live images of Earth’s surface during World War II (1939–1945). On October 4, 1957, Russia launched Sputnik 1 into orbit; it was about the size of a beach ball and emitted a faint beep every second or so as it circled Earth once every 96 minutes. Unexpectedly large numbers of people across North America and Europe tuned in radio receivers to hear these signals from space—a development that marked humanity’s entry into the Space Age. Just three weeks later Russia sent up another satellite called Sputnik 2; it carried a dog named Laika who became the first living creature in space but died after only seven days when her oxygen ran out (see also space exploration). Several nations built similar satellites in subsequent years: Vanguard 1 (U.S., 1958), Explorer 6 (U.S., 1959), Luna 3 (Soviet Union [USSR], 1959), Echo 1A (USSR/U.S., 1960), Ariel 1 (United Kingdom [UK], 1962), Telstar I and Relay I (both U.S./UK/France/Canada, 1962–1963), Syncom II and III (both U