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Satellite In the context of  spaceflight , a  satellite  is an artificial object which has been intentionally placed into  orbit . Such objects are sometimes called  artificial satellites  to distinguish them from  natural satellites  such as Earth's  Moon . In 1957 the  Soviet Union  launched the world's first artificial satellite,  Sputnik 1 . Since then, about 6,600 satellites from more than 40 countries have been launched. According to a 2013 estimate, 3,600 remained in orbit. [1]  Of those, about 1,000 were operational; [2]  while the rest have lived out their useful lives and become  space debris . Approximately 500 operational satellites are in  low-Earth orbit , 50 are in  medium-Earth orbit  (at 20,000 km), and the rest are in  geostationary orbit  (at 36,000 km). [3]  A few large satellites have been launched in parts and assembled in orbit. Over a dozen  space probes  have been placed into orbit around other bodies and become artificial satellites to the  Moon