BackForwardInstrument:  GLAS 

Instrument details
Acronym GLAS
Full name Geoscience Laser Altimeter System
Purpose Polar ice sheet thickness and topography.  Also cloud top height and aerosol
Short description Two-wavelength lidar (532 and 1064 nm). A Stellar Reference System (SRS) that includes a star tracker and a Laser Reference System (LRS) provide accurate positioning and co-referencing of the pulses at the two wavelengths.
Background New development
Scanning Technique Nadir-only viewing, sampling at 170 m intervals along track, near continuous profiling
Resolution Horizontal: 66 m IFOV sampled at 170 m intervals along track.  Vertical: 10 cm surface, 200 m cloud top
Coverage / Cycle Global coverage in 91 d (orbit repeat cycle, with 8d and 33d sub-cycles) leaving cross-track 2.5 km gaps at 80° latitude, 15 km at equator
Mass 298 kg Power 300 W Data Rate 450 bps

 

Providing Agency NASA
Instrument Maturity Flown on an R&D satellite
Utilization Period: 2003 to 2010-08-14
Last update: 2017-03-31
Detailed characteristics
Satellites this instrument is flying on

Note: a red tag indicates satellites no longer operational, a green tag indicates operational satellites, a blue tag indicates future satellites

Instrument classification
  • Earth observation instrument
  • Active and radio-occultation sensor
  • Lidar (Doppler lidar, backscatter lidar, lidar Dial, lidar altimeter)
Mission objectives
Primary mission objectives
  • Coastal sea level (tide)
  • Geoid
  • Gravity field
  • Ice sheet topography
  • Ocean dynamic topography
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Tentative Evaluation of Measurements

The following list indicates which measurements can typically be retrieved from this category of instrument. To see a full Gap Analysis by Variable, click on the respective variable.

Note: table can be sorted by clicking on the column headers
VariableRelevance for measuring this variableOperational limitationsExplanation
Aerosol column burden4 - fairCloud sensitive.. Along-track only.Opportunity information from lidar altimeter
Aerosol mass mixing ratio5 - marginalCloud sensitive.. Along-track only.Opportunity information from lidar altimeter
Aerosol Optical Depth4 - fairCloud sensitive.. Along-track only.Opportunity information from lidar altimeter
Biomass3 - highCloud sensitive.. Index only.. Along-track only.Total biomass inferred from the canopy
Cloud drop effective radius5 - marginalLow-density cloud only.. Along-track only.Opportunity information from lidar altimeter
Cloud ice5 - marginalLow-density cloud only.. Along-track only.Opportunity information from lidar altimeter
Cloud ice (total column)5 - marginalLow-density cloud only.. Along-track only.Opportunity information from lidar altimeter
Cloud ice effective radius5 - marginalLow-density cloud only.. Along-track only.Opportunity information from lidar altimeter
Cloud liquid water (CLW)5 - marginalLow-density cloud only.. Along-track only.Opportunity information from lidar altimeter
Cloud liquid water (CLW) total column5 - marginalLow-density cloud only.. Along-track only.Opportunity information from lidar altimeter
Cloud optical depth5 - marginalLow-density cloud only.. Along-track only.Opportunity information from lidar altimeter
Cloud top height4 - fairAlong-track only.Opportunity information from lidar altimeter
Coastal sea level (tide)4 - fairCloud sensitive.. Along-track only.Opportunity information from sea-ice lidar altimeter
Freezing level height in clouds5 - marginalLow-density cloud only.. Along-track only.Opportunity information from lidar altimeter. Detected as discontinuity
Geoid2 - very highLong time series needed.. Along-track only.Geoid derived from multi-temporal analysis of lidar altimetry data
Glacier topography3 - highCloud sensitive.. Long time for mapping.. Along-track only.Specifically designed for sea ice elevation, also useful over land
Gravity field3 - highPartial information (geoid).Gravity field derived from multi-temporal analysis of lidar altimetry data
Height of the top of PBL3 - highCloud sensitive.. Along-track only.Opportunity information from lidar altimeter. PBL top detected as discontinuity
Height of the tropopause3 - highCloud sensitive.. Along-track only.Opportunity information from from lidar altimeter. Tropopause height detected as discontinuity
Ice sheet topography3 - highCloud sensitive.. Long time for mapping.. Along-track only.Specifically designed for sea ice elevation, also useful over land
Land surface topography3 - highCloud sensitive.. Long time for mapping.. Along-track only.Specifically designed for sea ice elevation, also useful over land
Melting layer depth in clouds5 - marginalLow-density cloud only.. Along-track only.Opportunity information from lidar altimeter. Detected as discontinuity
Ocean dynamic topography3 - highCloud sensitive.. Long time for mapping.. Along-track only.Opportunity information from sea-ice lidar altimeter
PSC occurrence3 - highAlong-track only.VIS/NIR lidar altimeter
Sea-ice elevation3 - highCloud sensitive.. Along-track only.VIS/NIR lidar altimeter specifically designed for ice elevation
Sea-ice thickness4 - fairCloud sensitive.. Change detection only.. Along-track only.VIS/NIR lidar altimeter specifically designed for ice elevation. Thickness inferred by ice model
Aerosol volcanic ash4 - fairCloud sensitive.. Along-track only.Opportunity information from lidar altimeter
Aerosol volcanic ash (Total column)3 - highCloud sensitive.. Along-track only.Opportunity information from lidar altimeter