Sentinel-3 STM Theoretical Performance assessment using a System Performance Simulator and a Ground Prototype Processor
Amarouche, Laiba¹; Dumont, Jean-Paul¹; Sicard, Philippe¹; Obligis, Estelle¹; Vernier, Anne¹; Urien, Stéphanie¹; Frery, Marie-Laure¹; Jourdain, Sylvain¹; Houpert, Alexandre²; Féménias, Pierre³; Picot, Nicolas⁴; Boy, François⁴; Loddo, Carolina⁵; Rebhan, Helge⁶; Mavrocordatos, Constantin⁶
¹CLS, FRANCE; ²TAS, FRANCE; ³ESA, ESRIN, ITALY; ⁴CNES, FRANCE; ⁵EUMETSAT, GERMANY; ⁶ESA, ESTEC, NETHERLANDS

In the frame of the development of the Sentinel-3 satellite, System Performance Simulator (SPS) and Ground Processors Prototype (GPP) have been developed for each instrument of the Surface Topography Mission (SRAL, MWR and GNSS). This activity is performed by CLS under Thales Alenia Space, ESA and CNES contracts with the support of several European companies (isardSAT, Deimos-P, GMV, ACS and UCL/MSSL). The objectives of these simulators/processors are the following:

Support the development and the validation of the operational level 0, level 1b and level 2 processors;

Support the development of the instruments;

Evaluate the end-to-end mission performances;

Support during the In Orbit Commissioning phase
To reach these objectives, two simulators/processors per instrument have been developed:

The Level 1 Ground Prototype Processors (GPP) which include the level 0, level 1b processing.

The Level 2 processor for ocean, land and ice surfaces.

The System Performance Simulators (SPS) which include the GPP and the simplified Level 2 (ocean and land level 2 processor) as well as other modules. The SPS is able to generate geophysical representative Mission data products and process them until Level 2 for performance assessment.
The main modules for the SRAL, MWR, GNSS, SPS are:

A scene generator which aims at describing the test scenario in terms of geophysical parameters (eg. a grid of scatterers over sea or land mapped to a DEM for Altimeter chain, ...);

An instrument simulator converting the scene parameters into engineering measurement using an instrument model. The outputs of these modules are the Instrument Source Packets;

A Level 0 and a level 1b processor prototype used to generate level 0 and level 1b products. This prototype is representative of the L1 processing module of the future operational ground segment;

A simplified L2 processing module to generate the level 2 parameters.

Several performance and analysis tools.
A first version of the SPS, GPP and L2 processor have been successfully delivered to TAS/ESA/CNES during 2011. New evolutions have been introduced to those processors during 2012.
This presentation will give an overview of Sentinel-3 SPS and GPP architecture and product content. The algorithms used in the Level 1 and Level 2 processings will be also described. A main focus will be devoted to the SRAL SAR mode specific algorithms (Pseudo-LRM mode, SAR mode SAMOSA retracker) and to the more recent geophysical models introduced (MSS CNES/CLS 11, ACE2 DEM, Surface Mask with 7 states built using GlobeCover …). This presentation will also provide the performance assessment theoretical results using the SPS and GPP modules.