Characterization of Tropical Rainforest for X-Band Spaceborne SAR Calibration Using Tandem-X Data

Tropical rainforests have been established by the SAR community as well-known calibration sites for the estimation and monitoring of the radar antenna pattern shape in elevation. Here, according to the hypothesis of isotropic scattering, the backscattering coefficient in terms of unit area perpendicular to the antenna, called gamma nought, is assumed to remain constant with respect to the incidence angle. Nevertheless, several studies using X- and C-band sensors have shown a slight dependency of the rainforest backscatter on the incidence angle, as well as on the ground target properties and meteorological conditions. The aim of this work is to present a statistical characterization of radar backscatter at X-band over the equatorial Amazon rainforest using TanDEM-X data, and to provide insights on how to best utilize radar backscatter data in this region for SAR calibration and modelling purposes.