Long Term Temporal Stability of Forest Scatterers at P-band: An Assessment based on Air- and Space-borne Data Sets

Abstract

Gabon's tropical forests, estimated to cover 89% of the country’s territory [1], play a major role in the global carbon cycle and climate regulation, particularly in terrestrial carbon storage. The ESA BIOMASS satellite, operating in the P-band, offers a unique opportunity to estimate the aboveground biomass and monitor forest dynamics on a global scale [2]. Long wavelength and 3-days repeat-pass of BIOMASS, allow to acquire the high-quality interferograms.

Interferometric coherence is intrinsically sensitive to the volumetric distribution of scatterers inside the resolution cell, and, therefore, also sensitive to the forest height and stored biomass. However, the interferometric coherence, is subject to temporal decorrelation, that can be either wind-induced or caused by dielectric changes in the scattering volume. The propagation through the ionosphere requires additional calibration processing steps, that can complicate the interpretation of temporal changes in the reflectivity volume.

In this context, the new AfriSAR airborne campaign is conducted in Gabon in November 2025, at the end of BIOMASS in-orbit commissioning. The campaign data allow to assess the temporal stability of P-band radar coherence during the BIOMASS acquisition, matching the temporal and interferometric baselines of the satellite.

This study therefore aims to quantify, model, and interpret the temporal decorrelation of the P-band radar signal using fully polarimetric and interferometric/tomographic airborne datasets and compare it to the one of BIOMASS. In addition, the long-term temporal coherence of several months and years will be assessed based on the previous AfriSAR campaigns in 2016 and 2023.