BELSAR-SCIENCE - Soil and crop monitoring from simultaneous mono- and bistatic radar observations

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Context and objectives

Belgium has been proposed by ESA to organize an airborne campaign (the first airborne SAR campaign ever taking place over its territory) to collect and exploit full-polarisation, L-band bistatic SAR, having in mind a persisting need to collect bistatic signatures and explore their possible use. The targeted application fields of the BelSAR campaign are soil moisture, agriculture and SAR science. The BelSAR campaign per se (herein referred to as “the campaign”), financed by ESA and coordinated by CSL, consisted in the specification, planning and organisation of the campaign carried out by MetaSensing (MS, an aircrafts and SAR operator company).  The campaign has been completed successfully in 2018 including simultaneous in situ data collection by the same partners than the BelSAR Science project.  As a follow up, the BelSAR Science project financed by Belspo and coordinated by UCLouvain, concerns the scientific exploitation of the L-band SAR bistatic and in situ data collected for agriculture and soil moisture, as well as for bistatic SAR science.

The overarching research objective is to explore the application potential of mono- and bistatic InSAR/PolInSAR products acquired in L-band. Five specific objectives focus on three fields of applications: change detection, hydrology, and agriculture.

  • Objective 1 – technical feasibility and sensitivity of SAR change detection based on coherence and on optimized PolInSAR coherence using bi-static acquisition (subtle changes as crop stage development change)
  • Objective 2 – assessment of  the sensitivity of the scattered signal towards surface roughness, soil moisture and incidence angle for different configurations of the bistatic configuration and of the impact of uncertainty in roughness parameters on the retrieved soil moisture.
  • Objective 3 – development of a soil moisture retrieval algorithm where roughness information is not required thanks to the bistatic radars forms the third objective.
  • Objective 4 – assessment of the potential of bistatic coherence and temporal maps time series obtained from mono- and bistatic image pairs with different polarisations to bring additional insight for biophysical variables retrieval (fresh biomass for wheat and maize) crops.
  • Objective 5 – definition of a strategy to separate out the soil contribution from the canopy contribution, possibly complemented by C-band observation

This exploratory research will lead to recommendations and technical specifications for future SAR missions potentially developed by the European Space Agency.

Project outcome

Expected scientific results

The expectation is first to validate and extend the current theoretical research about bistatic SAR and its potential for agricultural and soil monitoring. Then, to qualify the hypothesized added value provided by bistatic systems over traditional monostatic ones for change detection, and crop and soil monitoring. Lastly, to explore its application potential for the agricultural sector.

Expected products and services

New, accurate, and reliable soil moisture and crop biophysical variables retrieval algorithms, which can lead to improved means of crop and underneath soil monitoring for farmers, policy-makers, and other relevant organizations.