Sputnik 1 postcard. Artwork of Sputnik 1, the world's first artificial satellite, on a postcard issued by the communist government of the former Soviet Union. The text translates as 'pioneer of the cosmic era.' Sputnik 1 was launched on October 4th, 1957. The name Sputnik is Russian for 'travel companion' or satellite. The body was made from highly polished aluminium alloy sphere, measured 58 centimetres in diameter and weighed 83.5 kilos. It also had four long antennas attached. Sputnik 1 transmitted radio signals back to earth for a period of 21 days. The success of Sputnik 1 prompted the US government to enter the Space Race with the launch of Explorer-1 four months later.