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Instrument: GLAS : Geoscience Laser Altimeter System |
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Associated Platforms ICESAT Spectral/Frequency Information Wavelength Keyword: Visible Number Channels: 1 Channel Spectral/Frequency Coverage/Range: 0.532 micrometers (atmosphere) Wavelength Keyword: Near Infrared Number Channels: 1 Channel Spectral/Frequency Coverage/Range: 1.064 micrometers (surface) Related Data Sets View all records related to this instrument Description [Text Source: NASA GLAS Instrument Home Page, http://icesat.gsfc.nasa.gov/glasinstrument.php ] GLAS (the Geoscience Laser Altimeter System) is the first laser-ranging (lidar) instrument for continuous global observations of Earth, which will make unique atmospheric observations as an important component of the ESE climate change program. GLAS is a facility instrument designed to measure ice-sheet topography and associated temporal changes, cloud and atmospheric properties.and give us information on the height and thickness of radiatively important cloud layers which is needed for accurate short term climate and weather prediction. In addition, operation of GLAS over land and water will provide along-track topography. GLAS includes a laser system to measure distance, a Global Positioning System (GPS) receiver, and a star-tracker attitude determination system. The laser will transmit short pulses (4 nano seconds) of infrared light (1064 nanometers wavelength) and visible green light (532 nanometers). Photons reflected back to the spacecraft from the surface of the Earth and from the atmosphere, including the inside of clouds, will be collected in a 1 meter diameter telescope. Laser pulses at 40 times per second will illuminate spots (footprints) 70 meters in diameter, spaced at 170-meter intervals along Earth's surface. Heritage: MOLA Instrument Type: A three-laser system, with a single laser operating at any given time Scan Type: Nadir Viewing Dimensions: Telescope diameter is 1 m, instrument height is ~175 cm Mass: 300 kg Power: 330 W average Spatial Resolution: At 40 pulses per second, the centers of 70-m spots are separated in the along-track direction by 170 m for a 600-km altitude orbit; the cross-track resolution is determined by the ground-track repeat cycle and orbit control. Duty Cycle: 100% Thermal Operating Range: 20° ± 5°C Telescope FOV: Nadir only, 375 μrad and 160 μrad (0.532 μm) Instrument IFOV: ~70 m laser footprint at nadir Online Resources http://glas.gsfc.nasa.gov/ http://icesat.gsfc.nasa.gov/ http://nsidc.org/data/icesat/data.html Instrument Logistics Data Rate: ~450 kbps Instrument Start Date: 2003-01-12 Instrument Owner: USA/NASA |
