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The Geoscience Laser Altimeter System (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.
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GLAS is being developed by a partnership of NASA, industry, and
university teams. The smallest of the new Med-LiLe class of rockets, the
Taurus, will launch GLAS into an orbit at 590 km altitude and 94 degrees
inclination to the equator. GLAS utilizes advanced laser detection and
ranging, attitude sensing, and orbital-position-sensing technologies. The
spacecraft provides a highly autonomous, inertially stabilized platform
with advanced power, guidance, and propulsion systems to maintain the
critical performance required for repeated Earth observations. Its
designed lifetime is for 3 years of operation with a 5-year goal.
Successive spacecraft will acquire the 10 to 15 year data set planned for ESE.
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