A radar suite for ice sheet accumulation measurements and near-surface internal layer mapping

Abstract

Many satellite, airborne, and in situ observations have been made to better understand the mass balance of the ice sheets. Satellite missions such as GRACE, ICESat, and Cryosat provide broad coverage, but are only capable of collecting data at relatively coarse temporal and spatial resolutions [7] [8]. Satellite observations alone are not sufficient to fully understand all mechanisms responsible for changes in the overall ice sheet mass balance. While these are sufficient over much of the interior of the ice sheet, to understand and model the dynamics of fast flowing glaciers and the margins of the ice sheet, finer resolution data are required. Airborne platforms, especially autonomous platforms, allow for key regions of the ice sheets to be measured with fineresolution remote sensing instruments. These platforms provide more accurate ice thickness estimates, internal layer mapping, and ice-bedrock interface imaging [2].To address this gap in the observations, we are designing and developing an instrumentation suite to be deployed on crewed and uncrewed aircrafts. Here we will focus on two radars in the instrumentation suite: an accumulation radar and a radar altimeter. The altimeter will be capable of measuring surface elevation and near-surface internal layers to a depth of about 10 m. The accumulation radar will be capable of measuring internal layers to a depth of about 100 m. A previously developed 150 MHz radar depth sounder/imager will be used to map layers below 100 m, as well as the ice-bedrock interface. This radar is beyond the scope of this paper. Field data collection using these systems will be performed simultaneously, providing a fineresolution characterization of the ice sheet from surface to bedrock. The altimeter provides annual and short-term information on the accumulation, while the accumulation radar provides information on the decadal scale variability. The depth sounder provides information on the century scale variability. Initial data collection occurred during the early spring 2009 Greenland field season; additional data collection will continue during future campaigns both in Greenland and Antarctica. System refinements will allow for this suite to be deployed on uncrewed aerial vehicles (UAVs), also being developed at the Center for Remote Sensing (CReSIS) at the University of Kansas.

UAVs for Science in Antarctica

“…A distributed architecture was proposed, placing the transmitter/receivers along the wings of the UAV to satisfy the mass and volume constrains of the platform. The same team presented two radar sensors to fly with UAVs in polar regions, as described by Lewis et al (2009) [172]. The accumulator radar is intended to measure internal ice layers up to 100 m depth, while the altimeter radar measures surface relief and near-surface internal layers (up to 10 m).…”

Development of a multi-frequency airborne radar instrumentation package for ice sheet mapping and imaging

“…This instrument allows us to penetrate into the first 100-200 m of the ice sheet and map the internal layers with vertical resolution of about 60 cm. The system reported here is an improved version of a radar set previously developed by the authors and thoroughly described in [8]. We utilize stretch processing techniques (as opposed to the FM continuous wave <FMCW> scheme in [8]) to achieve a 320 MHz synthetic bandwidth.…”

“…The system reported here is an improved version of a radar set previously developed by the authors and thoroughly described in [8]. We utilize stretch processing techniques (as opposed to the FM continuous wave <FMCW> scheme in [8]) to achieve a 320 MHz synthetic bandwidth. We discuss the configuration of this asset and present sample field test results.…”