Classification of Sea Ice Types with Radar

Using a helicopter-borne multichannel scatterometer (accurately calibrated non-imaging radar), the feasibility of using synthetic aperture radar (SAR) images from present and near-future spaceborne sensors for assisting winter navigation in the Baltic Sea was investigated. Due to cloud cover and short days in the winter, visible/infrared satellite data cannot be used for Baltic ice mapping. In order to decrease the operating cost of icebreakers, real-time radar-derived sea ice charts are needed to optimize the route selection of icebreakers assisting ships to Finnish and Swedish harbors. For ship navigation, information on (1) new ice and open water (preferred route), (2) level ice (second choice) and (3) ice ridges and rubble fields (should be avoided; may stop an icebreaker) is of primary importance. Four helicopter-borne radar campaigns were organized in 1988-1992 in order to experimentally study the radar response to different Baltic ice types. Measurements for six ice categories and open water were conducted under various weather conditions (wet and dry ice and snow surfaces). Based on the experimental data set, (1) the optimum radar parameters for Baltic ice mapping were determined, followed by three additional recommended systems, and (2) the feasibility of using synthetic aperture radar (SAR) images from present (ESA ERS-1 satellite) and near-future (ESA ERS-2 satellite, U.S. SIR-C Shuttle mission and Canadian Radarsat satellite) missions for discriminating sea ice categories was evaluated.