satellite, artificial

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satellite, artificial Artificial object placed in orbit around the Earth or other celestial body. Satellites can perform many tasks, including sending back data or pictures to the Earth. Hundreds of satellites of various types orbit the Earth. They may study the atmosphere, or photograph the surface for scientific or military purposes. Communications satellites relay radio, television, telephone, telegraph, and data signals from one part of the Earth to another. Navigation satellites transmit radio signals that enable navigators to determine their positions. The global positioning system (GPS) uses satellites in this way. Geodetic satellites are used to make accurate measurements of the Earth's size and shape. Sputnik 1 was the first artificial satellite, launched on October 4, 1957.

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