Sputnik 1

Sputnik 1 was the first man-made satellite to be launched into orbit, on October 4, 1957. The satellite had a weight of about 83 kg (184 pounds). It had two radio transmitters. It is believed that it orbited Earth at about 250 km (150 miles) above Earth's surface. Analysis of the radio signals were used to gather information about the upper atmosphere. The Sputnik was launched by an R-7 rocket.

Sputnik was the first of several satellites in the Soviet Unions Sputnik program, the majority of them successful. Sputnik 2 followed as the second satellite in orbit, also the first to carry an animal, the dog Laika. The first failure occurred with Sputnik 3[?].

The United States had also been working on satellites, primarily by teams working for the US Navy as Project Vanguard. Their first launch had originally been intended to launch before Sputnik, but was delayed several times before blowing up on the pad. A rush effort then started under the US Army's Jupiter project and succeeded launching Explorer I in January. This is considered the start of the Space Race between the two superpowers, as an aspect of the Cold War. Both nations kept on attempting to beat each other in space exploration, eventually culminating in the launch of the Apollo 11 mission to the Moon. Sputnik 1 fell back to Earth on January 4, 1958.

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See also: Space exploration, Unmanned space mission
Hear also: a recording of Sputnik's telemetry signal