Development and Initial Evaluation of the Tower-based Borealscat-2 P- and L-Band Tomographic SAR

This paper describes the development and initial evaluation of the BorealScat-2 radar. It is installed on a 50 m tall tower at a boreal forest site in northern Sweden and acquires tomographic and multi-polarization measurements at P- and L-band every 5 min. It is of the same design as its predecessor BorealScat except that the antenna frame can be moved along a 4 m horizontal track. A moveable antenna position is motivated by the need to acquire independent samples to reduce backscatter fluctuations. It also enables focused 3D imaging by combing tomographic and SAR processing when the backscatter fluctuations are temporally stable. We show results from data acquired in 2022, which demonstrates 3D imaging of a forest as well as the response from a trihedral.

1. INTRODUCTION

Satellite Synthetic Aperture Radar (SAR) provides high-resolution radar images with large area coverage. However, temporal resolution is poor and revisit times at the equator are typically one or several weeks for contiguous spatial coverage. Such long revisit times are not sufficient to resolve many geo- and biophysical processes of interest. Tower-based radars can fill this gap and provide time series of radar data with high temporal resolution, although with limited spatial coverage. Nevertheless, the high temporal resolution of the time series data is important for understanding of the physical processes involved and improving forward modeling with environmental data as input. Tower-based radar data can also be used for improving geo- and biophysical parameter retrieval from satellite SAR data, i.e. for improving inverse modeling such as estimation of above-ground biomass or tree water dynamics.