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