ICESat

ICESat. The Ice, Cloud, and land Elevation Satellite was a NASA mission dedicated to measuring polar ice sheet mass balance, cloud and aerosol heights, as well as land topography and vegetation characteristics. Launched in 2003, it provided critical data for understanding changes in the Earth's cryosphere and climate system. The satellite's primary instrument was the Geoscience Laser Altimeter System, a spaceborne lidar system that revolutionized precise elevation measurements from orbit.

Overview

The mission was developed under NASA's Earth Observing System as part of a broader effort to monitor global environmental change. Managed from Goddard Space Flight Center, the spacecraft bus was built by Ball Aerospace & Technologies. ICESat operated in a near-polar orbit, allowing it to cover the Greenland ice sheet and Antarctic ice sheet repeatedly. Its data became a cornerstone for studies of sea level rise and the contribution of melting glaciers, complementing other missions like GRACE.

Mission and objectives

The primary scientific goal was to determine the mass balance of the polar ice caps and understand their interaction with global climate change. Specific objectives included measuring ice sheet elevation changes with high precision, profiling the vertical structure of clouds and atmospheric layers, and mapping global land topography. The mission also aimed to collect data on canopy heights in forests to estimate biomass and carbon cycle fluxes. These measurements were vital for validating models used by the Intergovernmental Panel on Climate Change.

Instrumentation

The sole instrument was the Geoscience Laser Altimeter System, a sophisticated lidar system designed and built at NASA Goddard Space Flight Center. GLAS emitted short pulses of infrared and visible green laser light towards the Earth's surface. By precisely timing the round-trip of the reflected light, it calculated distance with extraordinary accuracy. The system also measured the backscattered signal from the atmosphere, providing profiles of cloud and aerosol layers. The instrument's performance was affected by the gradual degradation of its laser diodes, leading to operational changes from continuous to campaign-style measurements.

Data products and applications

The satellite generated a suite of data products, including global elevation maps of ice sheets, sea ice freeboard measurements, and land surface altimetry. These datasets were used by organizations like the National Snow and Ice Data Center for tracking the thinning of Pine Island Glacier and the Jakobshavn Glacier. Atmospheric data contributed to studies led by the CALIPSO mission team. Furthermore, vegetation structure information supported research into deforestation in the Amazon rainforest and boreal forest carbon stocks.

ICESat-2

To continue the vital record, NASA developed a successor mission, ICESat-2, which launched in September 2018 aboard a Delta II rocket from Vandenberg Air Force Base. This advanced satellite carries the Advanced Topographic Laser Altimeter System, a photon-counting lidar that uses multiple beams to provide even higher-resolution measurements. ICESat-2 data is essential for ongoing assessments of ice loss in West Antarctica and Greenland, and it supports international climate initiatives like those undertaken by the European Space Agency's CryoSat-2.

Category:NASA satellites Category:Earth observation satellites Category:Spacecraft launched in 2003