Sputnik 1 was the first artificial satellite, launched by the Soviet Union in 1957. It lifted off on 4 October 1957 from the Baikonur launch site in the Kazakh Soviet Socialist Republic, beginning humanity's first successful orbital mission.
The satellite was a polished aluminium sphere about 58 centimetres in diameter, fitted with four external antennas. Its radio transmitters sent regular beeping signals that could be detected around the world. Sputnik 1 orbited Earth roughly every 96 minutes, allowing scientists to study the upper atmosphere and the way radio signals travelled through the ionosphere.
Its launch shocked the United States and intensified the Cold War Space Race. Sputnik 1 transmitted for about 22 days before its batteries ran out, but it remained in orbit until 4 January 1958, completing approximately 1,440 orbits. Sputnik 2 followed in November 1957 and carried Laika, the first dog to orbit Earth. Explorer 1 was the first US satellite, launched in January 1958, while Vostok 1 was a crewed spacecraft.