Radar Backscatter from Arctic Sea Ice During IAOE 91

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Radar backscatter measurements were performed by the University of Kansas Radar Systems and Remote Sensing Labora- tory (RSL) from aboard the US Coast Guard icebreaker USCGC Polar Star as a part of the International Arctic Ocean Fkpedition (IAOE)'91 campaign. Measurements were performed for a period of two weeks during the early stages of the fall freeze-up in late August 1991. A dual-frequency scatterometer operating at 6.2 GHz and 11.3 GHz was used to measure radar backscatter of second-year, multi-year, and new ice types. The scatterorneter consisted of two frequency-modulated continuous-wave (FM-CW) radars. These were fed into a single, narrow-beam, offset-feed parabolic reflector antenna to obtain simultaneous dual-frequency measurements. Measurements were taken with all four linear polarization combina- tions at angles of incidence ranging from 20 to 65. Measurements were taken as the ship traversed in an area directly north of Spitzbergen, from 82 North latitude to nearly 85 N. at longitudes ranging from 30 to 40 E. In addition to the scatterometer measurements, small-scale roughness was measured by RSL. In support of the microwave program, characterization of sea-ice properties was performed by researchers from the U. S. Army Cold Regions Research and Engineering Laboratory (CRREL), and properties of the snow cover were measured by Microwave Group, Ottawa River, Canada (MWG). Preliminary results of these backscatter measurements and the relation of this backscatter to the physical properties of the snow cover and sea ice are presented.