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Key Facts

  • NASA Earth Observing System Facility Instrument : Geoscience Laser Altimeter System (GLAS)

  • Nadir-pointed laser altimeter; spacecraft enables off-nadir pointing capability

  • Measures polar ice-sheet topography and temporal changes in topography; cloud heights, planetary boundary heights, and aerosol vertical structure; and land and water topography

  • NASA/Goddard Space Flight Center in-house development of GLAS

  • Laser is diode pumped, Q-switched Nd:YAG laser with 40 Hz pulse repetition; 75 mJ at 1064 nm and 35 mJ at 532 nm

  • Receiver telescope is 1 meter diameter

  • Heritage: airborne and spaceborne laser altimetry and lidar systems; satellite laser ranging systems

  • GLAS completed Preliminary Design Review; Critical Design Review completed in March 1999

  • GLAS will be carried on ICESat (Ice, Cloud and land Elevation Satellite)

  • ICESat spacecraft delivery order signed February 1998, with Ball Aerospace, Boulder, CO; ICESat completed Mission Design Review in December, 1998

  • Orbit altitude is 600 km, near circular (frozen), 94 degree inclination

  • Verification orbit uses 8 day repeat pattern during first 120 days after launch

  • Mission orbit (post-verification) uses 183 day repeat pattern

  • Global Positioning System receiver provides 5 cm (radial) orbit position; ground-based laser ranging provides validation and backup

  • On-board star cameras and gyros provide spacecraft orientation and laser pointing direction

  • Launch no earlier than December 19, 2002, 16:45-17:30 PST

  • 3 year lifetime with 5 year goal

Last Update: March 27, 1999

Last Modified: Mon Jan 06, 2003