The aim of the CryoSat mission is to determine variations in the thickness of the Earth's marine ice cover and understand the extent to which the Antarctic and Greenland ice sheets are contributing global sea level rise.

To achieve these goals, CryoSat will primarily:

• determine regional trends in Arctic perennial sea-ice thickness and mass;
• determine the contribution that the Antarctic and Greenland ice sheets are making to mean global rise is sea level.

CryoSat's secondary goals are to observe:

• the seasonal cycle and inter-annual variability of Arctic and Antarctic sea-ice mass and thickness;
• the variation in the thickness of Earth's ice caps and glaciers.

Measurement goals

The following science and measurement requirements had been defined (for typical spatial scales) to be observed over different targets:

	Area [km2]	Science requirement [cm/year]	Measurement accuracy [cm/year]
Arctic sea ice	105	3.5	1.6
Ice sheets:
Regional scale	103	8.3	3.3
Antarctica	106	0.76	0.17

Observation mask showing target areas

CryoSatis designed to be fully automated such that its three measurement modes would be switched on-board according to the geographic chart. Low Resolution Mode (LRM) would have been operated over the light-blue areas of the ice-sheet plateaux and over the oceans. Synthetic Aperture Radar (SAR) mode would have been exploited over medium-blue sea-ice areas (the chart would have been updated every month for seasonal changes in sea-ice extent). SAR Interferometric (SARIn) mode will be used over the dark-blue steeply sloping ice-sheet margins, small ice caps and areas of mountain glaciers. The red areas on the chart indicate where calibration and validation activities will be carried out.