A radar altimetry is an instrument which purpose is measure the topography of the ocean surface.
Classical radar altimeters were pulse limited, and then the use of Synthetic Aperture Radar (SAR) techniques were introduced in conventional altimetry, in order to improve the current altimetric products.
The main innovation introduced by a SAR altimeter is the addition of along track processing, allowing an improvement of the resolution and multi-look processing (higher number of independent looks), which is translated in a reduction of the speckle noise effects, and thus in an improvement of the SNR, and of the minimum attainable range accuracy.
Cryosat-2 has been the first satellite working in SAR altimetry mode, confirming its data the oceanographic capabilities of the SAR altimetry. In this scenario, projects such as SAMOSA and CP40 have contributed to develop and test processing algorithms over the marine domain, allowing these studies to provide unbiased geophysical parameters estimation (e.g. Sea Surface Height (SSH), or Significant Wave Height (SWH)). Additionally, algorithms to mitigate the effect of the land contamination in coastal altimetry, has been also studied, being developed new coastal retracker for Coastal zones.
All this improvements done in the framework of the CryoSat-2 mission, will be implemented and adapted to the future ESA missions (Sentinel-3 and Sentinel-6/Jason-CS GPP), which are radar altimeters missions which aims to provide high-precision and timely observations of the ocean topography.