The Geoscience Laser Altimeter System (GLAS) is the sole instrument on the Ice, Cloud, and land Elevation Satellite (ICESat). The main objective of the ICESat mission is to measure ice sheet elevations and changes in elevation through time. Secondary objectives include measurement of cloud and aerosol height profiles, land elevation and vegetation cover, and sea ice thickness. ICESat will enable scientists to study the Earth's climate and, ultimately, predict how ice sheets and sea level will respond to future climate change.

ICESat has a near-circular and near-polar 91-day orbit with a 33-day repeat cycle, at an altitude of approximately 600 km, providing global coverage between 86°N and 86°S.

The National Snow and Ice Data Center (NSIDC) archives and distributes 15 products, including Levels 1A, 1B, and 2 laser altimetry and atmospheric lidar data. The initial data stream is approximately 20 GB per day.