Sputnik 1. Composite image of Sputnik 1, the worlds first artificial satellite against a backdrop of the Moon above Earths horizon. The Sun and the Earth are reflected on the satellites surface. Sputnik 1 was launched on 4th October 1957 by the former Soviet Union. The name Sputnik is Russian for travel companion or satellite. The body was a highly polished aluminium alloy sphere which measured 58 centimetres in diameter and weighed 83.5 kilograms. 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 Explorer1 four months later.
