The AfriSAR Campaign: Tomographic Analysis With Phase-Screen Correction for P-Band Acquisitions

ESA's earth explorer BIOMASS mission is a P-band (432-438 MHz) synthetic aperture radar (SAR) using a combination of polarimetry and interferometric observations to quantify the vertical structure and biomass of global forests, with the primary focus on tropical forests. The methodology to map the vertical structure of the forest is based on multibaseline tomographic measurements from space. In this paper, we use data acquired by airborne sensors during the AfriSAR campaign in humid tropical forests of Africa to examine the potential of P -band tomographic SAR measurements in estimating forest parameters. We use data acquired by ONERA's P-band SAR system over the Lopé National Park in central Gabon during July 2015 to estimate vertical profiles. In processing the multibaseline data, we develop and implement a phase-screen correction methodology based on recent works by Tebaldini et al. to improve the quality of measurements by removing phase perturbations associated with platform motions and uncertainties in flight trajectories. The vertical structure estimated from the corrected tomographic measurements are then compared with small and large footprint light detection and ranging (Lidar) observations collected as part of the AfriSAR campaign. The results suggest that phase-screen correction can significantly improve the vertical profile of radar backscattered power to match the Lidar observations in detecting ground, vertical vegetation density, and total height of the forests across a variety of forest types and terrain complexity.