This event marks the launch of the Sputnik 12 satellite, a Soviet spacecraft launched in 1961. It was the first satellite to be launched as part of the Soviet Union's space exploration program. The satellite was used to study the Earth's atmosphere and to collect data on cosmic radiation. It
From Wikipedia
Sputnik 1, often referred to as simply Sputnik, was the first artificial Earth satellite. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957 as part of the Soviet space program. It sent a radio signal back to Earth for three weeks before its three silver-zinc batteries became depleted. Aerodynamic drag caused it to fall back into the atmosphere on 4 January 1958.