ICESat (short for Ice, Cloud, and Land Elevation Satellite) is a satellite launched by NASA on January 12, 2003, to collect data on everything from land topography and vegetation to information on aerosol levels. On board is a single monitoring device called the Geoscience Laser Altimeter System (GLAS). One of the chief missions of ICESat, however, is to find out how the planet’s ice sheets are changing.