Development and Optimization of Airborne FMCW Radar for High-Resolution Snow Depth Measurements

Abstract:

Snow cover on sea ice controls heat exchange between atmosphere and ocean, and snow accumulation is a key variable in the mass balance of ice sheets. Airborne ultrawideband (UWB) radars have been extensively used over the last decade for the measurement of snow thickness over sea ice and the annual accumulation over land ice. These UWB radars use frequency-modulated continuous-wave signals with low transmit power and a large bandwidth to obtain fine resolution. Although extensive measurements were made with surface-based radars on snow over land, very few studies were conducted with airborne systems.

The Remote Sensing Center (RSC) at the University of Alabama developed a new generation of FMCW snow radars with significantly improved performance for airborne snow measurements of alpine snow. We conducted extensive measurements with a UWB FM-CW radar on a Twin Otter aircraft over Grand Mesa, Colorado, in conjunction with detailed in-situ measurements. The results from these measurements show that we can measure the thickness of snow as thin as 3-4 cm and as thick as 2-3 m. We successfully measured snow covered with more than 5-10 m vegetation. We have also developed a much-improved system for extensive measurements during November 2020 deployment. We developed systems for operation on manned as well as unmanned aircraft. We developed these radars to obtain nearly ideal impulse response without extensive additional processing so that the data collected can be processed in near real-time to produce results within 6-24 hours after the completion of a flight. We will present results from data collected from the 2019 field program, discuss the design and development of improved radar, and present new results from our planned Fall 2020 field program.