BIOMASS 3D Reflectivity Reconstructions for Forest Structure Mapping: Early Mission Results

Abstract

BIOMASS is collecting for the first time quad-pol tomographic SAR (TomoSAR) data from space for the reconstruction of 3D radar reflectivity at P-band, providing the unique opportunity to characterize 3D forest structure at global scale. The information content in terms of forest structure of BIOMASS 3D reflectivity reconstructions is determined by two critical aspects. The first one is the low range resolution caused by the 6 MHz bandwidth, which in turn limits the achievable TomoSAR resolution. The second one is the 3-day repeat-pass implementation which induces temporal decorrelation e.g. from either scatterer movements inside the resolution cells due to wind or dielectric changes from one satellite pass to the next. Larger values of temporal decorrelation can decrease the vertical separation capability and the radiometric accuracy of the reconstruction. The objective of this work is to evaluate BIOMASS TomoSAR reconstructions to obtain a first direct understanding of their potentials for forest structure mapping. Preliminary conclusions are expected on the impact of the reduced vertical resolution and the robustness to reflectivity variations induced by dielectric changes from pass to pass. Acquisitions in the commissioning phase and in the first tomographic cycles are used over a variety of forest sites with different structural characteristic and subject to different levels of dielectric changes in time. If possible, besides lidar data, first results from the BIOMASS validation campaign AfriSAR 3 / GABONX 2025 in Gabon will support the analysis. In November 2025, DLR’s airborne platform is acquiring interferometric / TomoSAR measurements in correspondence of a few BIOMASS passes over the La Lope National Park, providing a unique opportunity for comparing BIOMASS TomoSAR reconstructions with high-resolution temporal decorrelation-free ones.