UAS-Based Radar Sounding of the Polar Ice Sheets

Both the Greenland and Antarctic ice sheets are currently losing mass and contributing to global sea level rise. To predict the response of these ice sheets to a warming climate, ice-sheet models must be improved by incorporating information on the bed topography and basal conditions of fast-flowing glaciers near their grounding lines. High-sensitivity, low-frequency radars with 2-D aperture synthesis capability are needed to sound and image fast-flowing glaciers with very rough surfaces and ice that contains inclusions. In response to this need, CReSIS developed an Unmanned Aircraft System (UAS) equipped with a dual-frequency radar that operates at approximately 14 and 35 MHz. The radar transmits 100-W peak power at a pulse repetition frequency of 10 kHz, operates from 20 W of DC power, and weighs approximately 2 kg. The UAS has a take-off weight of about 38.5 kg and a range of approximately 100 km per gallon of fuel. We recently completed several successful test flights of the UAS equipped with the dual-frequency radar at a field camp in Antarctica. The radar measurements performed as a part of these test flights represent the first-ever successful sounding of glacial ice with a UAS-based radar. We also collected data for synthesizing a 2-D aperture, which is required to prevent off-vertical scatter, caused by the rough surfaces of fast-flowing glaciers, from masking bed echoes. In this article, we provide a brief overview of the need for radar soundings of fast-flowing glaciers at low-frequencies and a brief description of the UAS and radar. We also discuss our field operations and provide sample results from data collected in Antarctica. Finally, we present our future plans, which include miniaturizing the radar and collecting measurements in Greenland.