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Instrument: GLAS : Geoscience Laser Altimeter System
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Associated Platforms

Spectral/Frequency Information
Wavelength Keyword: VISIBLE
Number Channels: 1
Spectral/Frequency Coverage/Range: 0.532 micrometers (atmosphere)

Wavelength Keyword: NEAR INFRARED
Number Channels: 1
Spectral/Frequency Coverage/Range: 1.064 micrometers (surface)

Related Data Sets
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[Text Source: NASA GLAS Instrument Home Page, ]

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 5C
Telescope FOV: Nadir only, 375 ?rad and 160 ?rad (0.532 ?m)
Instrument IFOV: ~70 m laser footprint at nadir

Online Resources

Instrument Logistics
Data Rate: ~450 kbps
Instrument Start Date: 2003-01-12
Instrument Owner: USA/NASA