Advances made in Prototyping a Sentinel-3 Hydrologic Altimetry Processor

The SHAPE project (Sentinel-3 Hydrologic Altimetry Processor prototypE) is part of SEOM, Scientific Exploitation of Operational Missions, an ESA programme element which aims at expanding the international research community, strengthening the leadership of the European EO research community and addressing new scientific researches.

This Research and Development study is to prepare for the exploitation of Sentinel-3 over inland surface waters, while the Sentinel-3 PDGS has been designed for oceanography.

The objective is clearly to produce accurate and precise river stage, river discharge and lake level from the SRAL altimeter onboard Sentinel-3 and the HYPE hydrological model, over predefined test sites.

This requires to design and assess the impact of alternative and innovative techniques not implemented in the Sentinel-3 ground segment (there is NO Inland Water dedicated processing).

Because the project has been started before the release of the first Sentinel-3A data it has been designed so as to transpose results obtained from Cryosat-2 data (similar processing options as for Sentinel-3 except those benefiting from innovative techniques). The water levels are then migrated to the Sentinel-3 framework (from the geodetic orbit to the river/lake crossings of the Sentinel-3 repeat passes).

The test sites are described. An overview of the SHAPE processor is given and the innovative bricks are indicated : starting from the order of some low level steps (stacking, geometric corrections and range compression), going to the adapted SAMOSA retracker (and showing a comparison of retracker performances in SAR mode), mentioning the efforts that are done for the assimilation of spaceborne water levels into a semi-distributed model, and showing the efforts made in producing and using tightly codated High Resolution water masks derived from Sentinel-1 since Sentinel-1 and Sentinel-3 offer a nice synergistic framework.