The objective of the ESA SEOM Exploit-S-1 project has been to demonstrate and quantify the capabilities of the Sentinel-1 (S-1) mission to support the systematic surface soil moisture (SSM) generation at high resolution and regional/continental scale. Moreover, the consistency and complementarity between S-1 SSM and ESA/SMOS, NASA/SMAP and EUMETSAT/ASCAT SSM products have been assessed. The scientific relevance of satellite high-resolution SSM measurements for many applications (e.g., agriculture, hydrology, weather forecast, etc.) and the associated requirements - in terms of accuracy and temporal/spatial resolution - have been initially surveyed through a gap analysis based on interviews. In parallel, a review of the main Synthetic Aperture Radar (SAR) SSM retrieval methods proposed in the literature, with a specific emphasis on those exploiting single/dual polarized SAR data, has supported the selection of the SAR SSM retrieval methods. The most promising trade-off among robustness, retrieval accuracy and potential matching with the requirements of different applications have been identified into a suite of four SSM retrieval methods that have been tailored to S-1 data and implemented. A key component of Exploit-S-1 has been the extensive validation activity, likely unprecedented for a SAR SSM product at C-band. To this regard, Exploit-S-1 has benefitted from the advice and support of an External Advisory Team (EAT) consisting of International leading experts in microwave SSM retrieval and application that has provided their expertise in all the phases of the project and, particularly, in the validation phase. Exploit-S-1 has adopted the procedures and the metrics recommended by the Committee on Earth Observation Satellites (CEOS) Working Group on Calibration and Validation (WGCV) (https://lpvs.gsfc.nasa.gov/). In particular, the implemented validation activity has included i) a comparison of S-1 SSM estimates against in situ observations collected over seven cal/val sites located in USA, Canada, Australia and Europe (referred to as "validation at local scale") and ii) a cross-comparison among S-1, SMAP, SMOS and ASCAT SSM fields observed over a large area of the Mediterranean basin (referred to as "validation at regional scale"). In this study, an emphasis has been put on addressing the spatial representativeness error for S-1 SSM retrieval at 1 km. Based on the specific characteristics of each retrieval approach, a sensitivity analysis and the assessment of the performance of the algorithms on the experimental data basis, one method has been selected as the most promising approach for a pre-operational S-1 SSM product and its production has been extended over the entire Mediterranean basin.
Exploitation of S-1 for Surface Soil Moisture Retrieval at High Resolution - Executive Summary
Francesco Mattia;Anna Balenzano;Giuseppe Satalino;Francesco Lovergine;
2020
Abstract
The objective of the ESA SEOM Exploit-S-1 project has been to demonstrate and quantify the capabilities of the Sentinel-1 (S-1) mission to support the systematic surface soil moisture (SSM) generation at high resolution and regional/continental scale. Moreover, the consistency and complementarity between S-1 SSM and ESA/SMOS, NASA/SMAP and EUMETSAT/ASCAT SSM products have been assessed. The scientific relevance of satellite high-resolution SSM measurements for many applications (e.g., agriculture, hydrology, weather forecast, etc.) and the associated requirements - in terms of accuracy and temporal/spatial resolution - have been initially surveyed through a gap analysis based on interviews. In parallel, a review of the main Synthetic Aperture Radar (SAR) SSM retrieval methods proposed in the literature, with a specific emphasis on those exploiting single/dual polarized SAR data, has supported the selection of the SAR SSM retrieval methods. The most promising trade-off among robustness, retrieval accuracy and potential matching with the requirements of different applications have been identified into a suite of four SSM retrieval methods that have been tailored to S-1 data and implemented. A key component of Exploit-S-1 has been the extensive validation activity, likely unprecedented for a SAR SSM product at C-band. To this regard, Exploit-S-1 has benefitted from the advice and support of an External Advisory Team (EAT) consisting of International leading experts in microwave SSM retrieval and application that has provided their expertise in all the phases of the project and, particularly, in the validation phase. Exploit-S-1 has adopted the procedures and the metrics recommended by the Committee on Earth Observation Satellites (CEOS) Working Group on Calibration and Validation (WGCV) (https://lpvs.gsfc.nasa.gov/). In particular, the implemented validation activity has included i) a comparison of S-1 SSM estimates against in situ observations collected over seven cal/val sites located in USA, Canada, Australia and Europe (referred to as "validation at local scale") and ii) a cross-comparison among S-1, SMAP, SMOS and ASCAT SSM fields observed over a large area of the Mediterranean basin (referred to as "validation at regional scale"). In this study, an emphasis has been put on addressing the spatial representativeness error for S-1 SSM retrieval at 1 km. Based on the specific characteristics of each retrieval approach, a sensitivity analysis and the assessment of the performance of the algorithms on the experimental data basis, one method has been selected as the most promising approach for a pre-operational S-1 SSM product and its production has been extended over the entire Mediterranean basin.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
