ALT
Published: March 29, 2010, 12:00 am
Updated: November 4, 2011, 9:02 am
This article has been reviewed by the following Topic Editor:
C Michael Hogan
TOPEX/POSEIDON satellite. Source: NASA
ALT is an acronym for the radar altimeter used on the TOPEX/POSEIDON mission. The ALT was the first spaceborne dual–frequency altimeter and is the primary instrument for the mission. The payload mass of this instrumentation package was 206 kilograms.
| This article is written at a definitional level only. Authors wishing to expand this entry are inivited to expand the present treatment, which additions will be peer reviewed prior to publication of any expansion. |
Measurements are made at two frequencies, 5.3 and 13.6 GigaHertz (GHz) and combined to minimize the errors caused by the presence of ionospheric free electrons, the total content of which is obtained as a by–product of the measurement. This instrument was based on previous Seasat and Geosat altimeters with several improvements including the 5.3 GHz channel for the ionospheric measurement, more precise height measurement, and a longer system lifetime. In October 2005, after 62,000 orbits of Earth, the mission ended when the spacecraft lost its ability to maneuver, bringing to a close history's longest Earth-orbiting radar mission.
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Citation
Steve Baum (Lead Author);Peter Saundry (Contributing Author);C Michael Hogan (Topic Editor) "ALT". In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth March 29, 2010; Last revised Date November 4, 2011; Retrieved May 26, 2013 <http://www.eoearth.org/article/ALT>
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Assistant Research Scientist, Physical Section
Department of Oceanography
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TOPEX/POSEIDON satellite. Source: NASA
ALT is an acronym for the radar altimeter used on the TOPEX/POSEIDON mission. The ALT was the first spaceborne dual–frequency altimeter and is the primary instrument for the mission. The payload mass of this instrumentation package was 206 kilograms.
| This article is written at a definitional level only. Authors wishing to expand this entry are inivited to expand the present treatment, which additions will be peer reviewed prior to publication of any expansion. |
Measurements are made at two frequencies, 5.3 and 13.6 GigaHertz (GHz) and combined to minimize the errors caused by the presence of ionospheric free electrons, the total content of which is obtained as a by–product of the measurement. This instrument was based on previous Seasat and Geosat altimeters with several improvements including the 5.3 GHz channel for the ionospheric measurement, more precise height measurement, and a longer system lifetime. In October 2005, after 62,000 orbits of Earth, the mission ended when the spacecraft lost its ability to maneuver, bringing to a close history's longest Earth-orbiting radar mission.
Further Reading:
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