Sputnik (Russian: ‘fellow traveller’)
A 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, was 58 cm 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 Sputniks were superseded in the early 1960s by the Cosmos series.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 and had on board the dog Laika, the first living creature in space. Later, Sputniks were test flights of the Vostok spacecraft.