In the context of spaceflight, a satellite is an object which has been placed
into orbit by human endeavour. Such objects are
sometimes called artificial
satellites to distinguish
them from natural satellites such as the Moon.
The world's first artificial
satellite, the Sputnik 1, was
launched by the Soviet Union in 1957. Since then, thousands of satellites have
been launched into orbit around the Earth;
also some satellites, notably space
stations, have been launched in parts and assembled in orbit. Artificial
satellites originate from more than 50 countries and have used the satellite
launching capabilities of ten nations. A few hundred satellites are currently
operational, whereas thousands of unused satellites and satellite fragments
orbit the Earth as space debris.
A fewspace probes have been
placed into orbit around other bodies and become artificial satellites to the
Moon, Mercury, Venus, Mars, Jupiter,Saturn, and the Sun.(...)






