What is Geoscience Laser Altimeter System (GLAS)?
The Geoscience Laser Altimeter System (GLAS) is a next-generation space lidar. It is the sole scientific instrument on ICESat. GLAS combines a precision surface lidar with a sensitive dual wavelength cloud and aerosol lidar. GLAS has 3 lasers that emit infrared and visible laser pulses at 1064 and 532 nm wavelengths. These lasers operate at eye-safe signal levels but only one will operate at any given time. The Geoscience Laser Altimeter System (GLAS) uses a laser to measure ice sheet height, land topography, cloud height, aerosols, and the structure of vegetation canopies. GLAS measures topography by timing pulses of laser light bounced off the Earth’s surface, a technique called Light Detection and Ranging (LIDAR). (Photograph courtesy ICESat Science Team) On orbit, GLAS continuously emits laser pulses at a rate of 40 per second from the Earthfacing (nadir) side of ICESat. GLAS measures precisely how long it takes for photons in a laser pulse to pass through the atmosphere to the Ear
