| Geostationary satellites orbit the Earth's axis as fast as the
Earth spins. They hover over a single point above the Earth at an
altitude of about 36,000 kilometers (22,300 miles). To maintain constant
height and momentum, a geostationary satellite must be located over
the equator. Scientists determined this position by using Newton’s
Law of Gravity. The same force that makes apples fall from trees on
Earth is the force that keeps the satellite in its orbit. Sir Isaac
Newton realized that the force of gravity depends on the masses of
the objects involved (more massive objects feel a stronger gravitational
force), and the distance between the objects involved (objects which
are close together feel a stronger gravitational force).
The United States typically operates two geostationary satellites
called GOES (Geostationary Operational Environment Satellite). One
has a good view of the East Coast; the other is focused on the West
Coast. Another satellite in geostationary orbit is the European
METEOSAT (METEOrological SATellite), which views the eastern Atlantic
Ocean, Africa, and Europe. The Japanese GMS (Geostationary Meteorological
Satellite) has a good view of Asia, Australia, and the western Pacific
Ocean.
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