Series of ten Soviet Earth-orbiting satellites launched from 1957 by R-7 rockets. Sputnik 1 was the first artificial satellite, launched on 4 October 1957. It weighed 84 kg/184 lb, with a 58 cm/23 in diameter, and carried only a simple radio transmitter, which allowed scientists to track the spacecraft as it orbited Earth. It burned up in the atmosphere 92 days later. The Sputnik research team was headed by Sergei Korolev
. Sputniks were superseded in the early 1960s by the Cosmos series.
Sputnik 2, launched on 3 November 1957, weighed about 500 kg/1,100 lb and had on board the dog Laika, the first living creature in space. There was no provision for returning the dog to Earth, and it died in space. Later Sputniks were test flights of the Vostok
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