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What is a Ground Control Station?

Artist's Conception of Terra Satellite Orbiting Earth
A 21st Century Satellite Orbiting Earth

All kinds of satellites -- weather, observation, navigation, communications -- must stay in touch with someone on the ground. The work of satellites orbiting hundreds or thousands of miles above our planet is directed by human operators in "ground control stations" on Earth.

Ground control stations are located all around the globe. To tell an unmanned spacecraft what to do, controllers send coded radio signals to the satellite and receive similar signals from it.

For instance, a newly-orbiting satellite can be told to unfold its electrical solar panels and communication antennas and turn on science instruments. Ground controllers can instruct an observation satellite to look elsewhere. A weather satellite might be told to stare at a hurricane. The radio frequency used by a communications satellite to beam down a TV movie can be changed. A spysat can be ordered to modify its orbit to fly its sensors over specific ground targets.

NASA controls its constellation of TDRS communication satellites from a ground station in White Sands, New Mexico. Many military satellites are operated from ground control stations in Colorado and California.

NASA's deep-space interplanetary probes operate in far-flung regions of the Solar System -- Magellan at Venus, Galileo approaching Jupiter, Ulysses crossing the Sun, the twin Voyagers at the far outer edge of the System. All are controlled from NASA's Jet Propulsion Laboratory in Pasadena, California, through three giant satellite dish antennas in California, Spain and Australia.

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