Exploitation of Sentinel-1 for Surface Soil Moisture Retrieval at High Resolution (Exploit-S-1)
The C-band Sentinel-1 (S-1) European Radar Observatory, with its two satellites (S-1A & B), is the only operating SAR mission with monitoring capabilities, frequent revisit and large geographical coverage that will guarantee data continuity over the next decades. S-1 with its advanced observational capabilities opens new perspectives to SAR derived near surface soil moisture (SSM) products as, for the first time ever, they may attract a real interest in a wide user community and stimulate a synergistic interaction with SSM products at low resolution.
The scope of the two-year Exploit-S-1 project is to demonstrate the capabilities of the S-1 mission to support systematic SSM product generation at high resolution (e.g. 500m-1000m) and at regional/continental scale.
A suite of SSM retrieval methods will be developed, implemented and validated using S-1 data. The methods will be based on previous research into C-band soil moisture retrieval and will be selected from the great wealth of approaches proposed in the literature and tailored to S-1 data. The emphasis will be on implementing and comparing algorithms presenting the most promising trade-off among robustness, retrieval accuracy and potential matching with the requirements of different applications (e.g. Numerical Weather Prediction, hydrological forecasting, drought events …) in terms of accuracy, resolution and product frequency. In addition, the suitability of the algorithm to fully exploit the S-1 observational assets (e.g., dual polarization, spatial/temporal resolution, radiometric accuracy) in order to deliver a large scale mapping will be considered.
A key component of Exploit-S-1 will be the validation activity that will include local and regional scale sites (e.g. the Mediterranean basin) in order to better assess the potential for pre-operational and operational soil moisture products and services.
A further pivotal element of Exploit-S-1 will be the assessment of the optimal pre-processing of S-1 time series for SSM retrieval. This will also have the outreaching effect of consolidating standards for the generation of S-1 multi-temporal products that are well suited for other S-1 retrieval studies.
Finally, the Exploit-S-1 proposing team will be supported by an External Advisory Team (EAT) consisting of international leading experts in microwave SSM retrieval and application. Their role will be to advice the Exploit-S-1 team in all the phases of the project and, particularly, in the validation phase. In addition, they will support Exploit-S-1 through making available the in situ data collected over important validation sites of past/current cal/val activities related to low-resolution products from passive L-band and scatterometer systems (e.g. SMOS, SMAP and ASCAT).
