ICESat

ICESat, or Ice, Cloud, and land Elevation Satellite, is a NASA mission designed to measure changes in the Earth's ice sheets, land elevations, vegetation canopies, and cloud heights from space. The program has included two successive missions: ICESat and ICESat-2, each using laser altimetry to determine surface elevations with high precision.

The original ICESat was launched in 2003 and carried the GLAS (Geoscience Laser Altimeter System) instrument. GLAS emitted laser pulses toward the Earth's surface and recorded the time it took for the beams to return, enabling precise measurements of ice sheet elevations, land topography, and canopy structure, as well as insights into cloud and aerosol layers. ICESat contributed significantly to understanding ice sheet mass balance and sea level rise, and its data remain a valuable resource for climate research and geophysical studies. Operations continued until 2009, when the mission ended due to instrument limitations.

ICESat-2 was launched in 2018 to extend and improve the capabilities of its predecessor. It uses ATLAS, a photon-counting laser altimeter that operates with a green 532-nanometer laser and a multi-beam configuration. The instrument provides high-resolution elevation measurements of ice sheets, sea ice, land surfaces, and vegetation, enabling more frequent and detailed monitoring of elevation changes. ICESat-2 data support assessments of ice dynamics, hydrology, forest structure, and other cryospheric and terrestrial processes, and are distributed through NASA data centers for researchers worldwide.

Together, ICESat and ICESat-2 advance understanding of how polar and terrestrial surfaces respond to a warming climate, informing scientific knowledge, environmental monitoring, and policy discussions.