ESA’s Earth Explorer CryoSat mission, launched on 8 April 2010, is dedicated to precise monitoring of the changes in the thickness of marine ice floating in the polar oceans and variations in the thickness of the vast ice sheets that overlie Greenland and Antarctica. After the disappointments of the first mission attempt in 2005, the IPY community expressed strong support for this replacement mission. Congratulations to the entire CyroSat team!