Development of an airborne millimeter-wave FM-CW radar for mapping river ice

Abstract

Analyses of a river's freezeup ice cover stability and its breakup rely on detailed knowledge of the cover's thickness and the variability of that thickness. A high-resolution, millimeter wave (26.5- to 40-GHz) frequency modulated-continuous wave radar with real-time data acquisition and digital signal processing and display capability was deployed from a low-flying (3–10 m) helicopter to continuously acquire, process, and display data during an ice thickness profiling survey of a 24-km study reach. A nominal sheet ice thickness of 50 cm, occasional areas of new ice sheet as thin as 5 cm, open leads, and massive ice accumulations of the order of 5 m thick were encountered. Radar profiling data agreed with ground truth from borehole measurements of the sheet ice, and provided a more detailed view of the ice conditions than that obtained from a low altitude video survey. The radar system provided rapid, safe, and accurate data acquisition, allowing detailed mapping of the ice conditions throughout the reach. Key words: airborne, FM-CW radar, high-resolution radar, ice profiling, millimeter waves, radar remote sensing, river ice.