GEO typically stands for "Geosynchronous Equatorial Orbit" which is an orbit around the Earth that is located at an altitude of approximately 35,786 kilometers above the Earth's surface. This is the altitude at which a satellite's orbital period matches the period of the Earth's rotation, so the satellite appears to remain stationary in the sky as viewed from the ground. Geosynchronous orbit is often abbreviated as GSO.
Geosynchronous orbit is useful for certain types of satellites, such as communication satellites, because it allows them to remain over a fixed location on the Earth's surface at all times. This allows them to provide continuous coverage to a specific area, such as a particular region or continent. Geosynchronous orbit is also sometimes referred to as "geostationary orbit," although the terms are not strictly interchangeable.
There have been many famous satellites placed in geosynchronous orbit (GEO) over the years. Some examples include:
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The first satellite placed in GEO was Syncom 2, which was launched in 1963.
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The Communication Satellite Corporation (COMSAT) launched the first commercial communication satellite, INTELSAT I (also known as "Early Bird"), in 1965.
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In 1969, NASA launched the Applications Technology Satellite (ATS) to test new technologies in space.
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The first satellite to provide direct-to-home television service was RCA's Satcom 1, launched in 1975.
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The Hughes HS-376 satellite, launched in 1976, was the first geostationary satellite to be used for telephone and data communication.
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In 1984, the Inmarsat satellite system was launched to provide global mobile satellite communications for maritime, aviation, and land-based users.
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The first satellite in the Globalstar constellation was launched in 1990, providing satellite phone and data services.
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The first satellite in the Iridium constellation, a global mobile satellite communication system, was launched in 1997.
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In 2000, the European Space Agency (ESA) launched the Artemis satellite, which was used to test new technologies for satellite communication and navigation.
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The first satellite in the GPS (Global Positioning System) constellation was launched in 1978, and the system has since become a critical component of modern navigation and location services.