CryoSat is the first satellite of ESA's Living Planet Programme to be realized in the framework of the Earth Explorer Opportunity Missions. The mission concept was selected in 1999 with an anticipated launch in 2004. CryoSat is a radar altimetry mission dedicated to the observation of the polar regions. Its aim is to study possible climate variability and trends by determining the variations in thickness of the Earth's continental ice sheets and marine sea ice cover.