Since ice plays a crucial role in moderating Earth's climate and the effects of a changing climate are fast becoming apparent, particularly in the polar regions, it is important to understand exactly how Earth’s ice fields are responding.

For some years now, satellites such as ESA’s Envisat have been mapping the extent of ice cover and have shown that annual average Arctic sea-ice extent has shrunk by 2.7% per decade since 1978.

While these observations on ice extent provide invaluable data, this is only part of the picture. In order to understand fully how climate change is affecting these remote but sensitive regions, there remains an urgent need to determine exactly how the thickness of land and sea ice is changing. CryoSat is Europe's first mission to address this.

CryoSat-2 carries sophisticated technologies to measure changes at the margins of the vast ice sheets that overlay Greenland and Antarctica and marine ice floating in the polar oceans. By accurately measuring thickness change in both types of ice, CryoSat-2 will provide information to complete the picture and lead to a better understanding of the role ice plays in the Earth system.

Launched on 8 April 2010, CryoSat-2 is in a highly inclined polar orbit, reaching latitudes of 88° north and south, to maximise its coverage of the poles. Its main payload is an instrument called Synthetic Aperture Interferometric Radar Altimeter (SIRAL). Previous radar altimeters have been optimised for operations over the ocean and land, but SIRAL is the first sensor of its kind designed for ice.