Sputnik 3, Soviet postcard. Both the postmarks and the lefthand stamp (upper right) depict the Soviet spacecraft Sputnik 3 and its date of launch, 15 May 1958. The artwork at left shows a mythological figure launching Soviet spacecraft into orbit against a background of a Kremlin tower with its red star symbolising the Communist era. Sputnik 3 was a small unmanned conical spacecraft that carried scientific instruments to measure the upper atmosphere, cosmic rays, and the Earth's magnetic field. It was 3.57 metres long and 1.73 metres wide at the base.