మొదటి మానవరహిత ఉపగ్రహం ఏది ?
Sputnik 1 ( or ; "Satellite-1", or "PS-1", Простейший Спутник-1 or "Prosteyshiy Sputnik-1", "Elementary Satellite 1") was the first artificial Earth satellite. The Soviet Union launched it into an elliptical low Earth orbit on 4 October 1957, orbiting for three weeks before its batteries died, then silently for two more months before falling back into the atmosphere. It was a 58 cm (23 in) diameter polished metal sphere, with four external radio antennas to broadcast radio pulses. Its radio signal was easily detectable even by radio amateurs, and the 65° inclination and duration of its orbit made its flight path cover virtually the entire inhabited Earth. This surprise success precipitated the American Sputnik crisis and triggered the Space Race, a part of the Cold War. The launch ushered in new political, military, technological, and scientific developments.
Sputnik 1