Sentinel-3 Surface Topography Mission for Science
Benveniste, Jerome1; Donlon, Craig2; Klein, Ulf2; Borde, Franck2; Mavorcordatos, Constantin2; Rehban, Helge2; Féménias, Pierre1

Global Monitoring for Environment and Security (GMES) is a joint initiative of the European Commission (EC) and European Space Agency (ESA), which aims at achieving an autonomous and operational Earth observation capacity. GMES marks the transition from R&D oriented efforts in Earth observation towards operational services. The overall service duration is planned to be 20 years with several satellites. Currently, the launch of the first Sentinel-3 satellite is planned in 2014 and the second unit approximately 18 months later.
Sentinel-3 is an operational mission in high-inclination, low Earth orbit for the provision of observational data to marine and land monitoring services. These services include the generation of products aimed at the monitoring of land, inland water, ice fields and ocean. Full performance will be achieved with a constellation of two identical satellites, separated by 180 degrees in the same orbital plane. This configuration is driven by a trade-off between ocean and land observation requirements and operational constraints.
The operational character of the mission implies a high level of availability of the data products and fast delivery time. The Sentinel-3 spacecraft accommodates two large optical instruments - the Ocean and Land Colour Instrument (OLCI) and the Sea and Land Surface Temperature Radiometer instrument (SLSTR) – and a Surface Topography payload consisting of a SAR Radar Altimeter (SRAL), a Microwave Radiometer (MWR) plus a suite of instruments for precise orbit determination (POD), including DORIS and GPS, star trackers for precise attitude control, a mandatory feature for the accurate processing of the SAR altimeter data. Sentinel-3 will host both GPS and DORIS receivers, which will allow to provide independent POD estimates done by different teams. This is quite a unique feature of Sentinel-3 with respect to other altimeter missions and we will learn a lot from looking at the deltas in the orbit solutions. These instruments will ensure the continuation of important data streams established with ESA’s ERS-1, ERS-2 and ENVISAT satellites.
GMES Sentinel-3 is a series of operational satellites that will guarantee access to an uninterrupted flow of precision global data products. Together with the other Sentinels, this mission will fulfill the monitoring needs of the GMES marine and land services and climate research communities. The improved design of the topography and the optical payload and the corresponding data products will allow a data continuity the next decade.
This presentation will review the scientific applications and cutting-edge challenges of the Sentinel-3 Surface Topography payload for the open ocean, coastal zone, inland seas, inland water, land and cryosphere.