An Airborne Millimeter-Wave FM-CW Radar for Thickness Profiling of Freshwater Ice

The ability to profile rapidly and accurately the structure of freshwater ice down to a thickness of a few centimeters over large surfaces of frozen ponds, lakes and rivers has wide military, industrial, commercial and recreational application, including safety and trafficability surveys. A prototype broadband millimeter wave 26.5 to 40 GHz Frequency Modulated- Continuous Wave FM-CW radar, employing real-time data acquisition and Digital Signal Processing DSP techniques, has been developed for continuously recording the thickness profile of freshwater ice. Thickness resolution is better than 3 cm -10, which improves on short-pulse and FM-CW radars operating at frequencies less than 10 GHz. These other radars have a best reported thickness resolution of approximately 10 cm with a -10 accuracy this is insufficient because a freshwater ice sheet as thin as 5 cm, floating on water, can be safely traversed by an individual of average weight. System specifications include a 15-dBm output RF Radio Frequency power level, a 0. 066-second sweep rate and less than a 50dB Signal-to-Noise Ratio SNR. This radar was tested on the ground and from a helicopter at heights of up to 7 m above ice surfaces at speeds up to 40 kmhr. Pond and river ice sheets between 3 and 35 cm thick, with and without fresh snow cover, and with minimal surface roughness have been profiled. Results have shown direct correlation between radar and borehole thickness measurements. Losses from volume scattering by imbedded air bubbles did not significantly affect the systems capability to discern the airice and icewater scattering boundaries.... Field tests, Ice safety, Millimeter wave radar, Ice, Ice thickness profiling.