Currently there are approximately 2,465 artificial satellites orbiting the Earth. The world's first artificial satellite, Sputnik 1, was launched by the Soviet Union in 1957. Artificial satellites originate from more than 40 countries and have used the satellite launching capabilities of ten nations. A few hundred satellites are currently operational, but thousands of unused satellites and fragments orbit the Earth as space debris.

The United States Space Surveillance Network (SSN) has been tracking objects in Earth's orbit since the 1957 Soviet launch of Sputnik I. Since then, the SSN has tracked more than 26,000 objects. The SSN currently tracks more than 8,000 man-made orbiting objects. The rest have re-entered Earth's atmosphere and disintegrated, or survived re-entry and impacted the Earth.

The United States' Apollo 11 was the first manned mission to land on the Moon, on 20 July 1969. There have been six manned U.S. landings between 1969 and 1972 and many unmanned landings. The United States is the only country to have successfully conducted manned missions to the Moon.

A few space probes have been placed into orbit around other bodies and become artificial satellites to the Moon, Mercury, Venus, Mars, Jupiter, Saturn, Vesta, Eros, and the Sun. NASA's New Horizons deep space probe is now approaching Pluto after a 9 year journey of 3 billion miles.

Photo : NSSDC - NASA


26 Feb 2017 : : Spacecraft