Snow Depth Measurements With Ultra-Wideband Compact FMCW Radar on a Small Unmanned Aircraft System

This paper presents results from a field deployment of a small Unmanned Aircraft System (sUAS) radar in Colorado-Grand Mesa during Spring-2022 for measurements over snow. The stand-alone, low-power, compact, and Frequency Modulated Continuous Wave (FMCW) radar on a sUAS is used for these measurements. The radar operates over the frequency range of 2.8-5.8 GHz. The transmit signal is obtained by down-converting 77–81 GHz chirp generated with an automotive radar. The radar operates with a low output power of only 3 dBm (2 mW) to mitigate interference to nearby communication systems with a chirp duration of $250 \mu \text{s}$ . The received signal is up-converted back to 77–81 GHz for digitization and processing using the automotive radar data capture board. The radar data are processed with a fully focused Synthetic Aperture Radar (SAR) algorithm after applying phase and amplitude corrections to the transmitter chirp to obtain nearly ideal point target responses. The radar mapped air-snow and snow-ground surface interfaces as well as the snow internal layers with snow depth exceeding 2 m in areas covered with 15–25 m tall trees. In addition, the radar-generated snow thicknesses are within ±10 cm of in-situ measurements.