The first European Space Agency satellite dedicated to measuring the thickness of polar sea ice and monitoring changes in the ice sheets (cryosphere) that blanket Greenland and Antarctica with synthetic aperture radar. CryoSat was first Earth Explorer Mission craft to be selected in 1999, but the original satellite was lost due to a launch failure in October 2005. A new satellite (CryoSat-2) was subsequently built with a number of improvements and successfully launched on 8 April 2010 aboard a Dnepr rocket at Baikonur Cosmodrome. The satellite flies at an altitude of just over 700 km, reaching latitudes of 88 degrees north and south, to maximize its coverage of the poles. CryoSat-2 measures ‘freeboard’—the difference in height between sea ice and adjacent water—as well as ice-sheet altitude, tracking changes in ice thickness.