Lidar Altimetry

Lidar altimetry measures surface elevation by timing a laser pulse’s round trip rather than a radar pulse. NASA’s ICESat-2, launched 15 September 2018, carries the ATLAS photon-counting green laser, splitting into six beams and fixing elevation to a few centimeters, used for ice-sheet change, sea-ice freeboard, and clear-water bathymetry to roughly 40 m. The original ICESat flew the GLAS laser from 2003 to 2009. Compared with radar altimetry, the laser footprint is small, meters across, giving sharp spatial detail, but clouds block it. It complements the broad radar freeboard from CryoSat-2 and underpins polar elevation-change records.