Artificial Satellites

Geostationary Orbit

In 1928, Herman Potočnik, first proposed placing a satellite in an orbit around the Earth‘s equator with a period equal to the rotational (sidereal) period of the Earth; however, science fiction author Arthur C Clarke often is credited with popularising the idea in his 1945 paper entitled Extra-Terrestrial Relays – Can Rocket Stations Give Worldwide Radio Coverage?.

A satellite in such an orbit would remain at a fixed point over the Earth’s surface, and to an observer on Earth would appear to remain static at a fixed point in the sky. This would mean that a satellite receiver dish could be fixed in one position without having to track the satellite’s motion. This is now known as a geostationary or geosynchronous equatorial orbit.

Since the orbital period of a satellite is simply dependent upon the radius of the orbit from the centre of mass of the Earth, and not on the mass of the satellite, all geostationary orbits are of the same altitude, 35,786 kilometres (22,236 miles) above the Earth’s equator.

The first satellite placed in geostationary orbit was Syncom 3, launched on August 19, 1964.

Lagrangian Points

Lagrangian points are locations in space between two massive bodies, such as the Sun and the Earth or the Earth and the Moon, where the gravitation pulls of the two bodies exactly cancel each other out. A spacecraft placed as such a position would therefore require very little power in order to remain stationary at such a point.

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Astronomy, Cosmology, Astrophysics and Space Exploration

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