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Airborne River-ice Thickness Profiling with Helicopterborne UHF Short-pulse Radar

By A. Arcone and Allan J. Delaney

Abstract

ABSTRACT. The ice-thickness profiling performance of a helicopter-mounted short-pulse radar operating at approximate center frequencies of 600 and 900 MHz was assessed. The antenna packages were mounted 1.2 m off the skid of a smaII helicopter whose speed and altitude were varied from about 1.8 to 9 m / s and 3 to 12 m. Clutter from the helicopter offered minimal interference with the ice data. Data were acquired in Alaska over lakes (as a proving exercise) and two rivers, whose conditions varied from open water to over 1.5 m of solid ice with numerous frazil-ice formations. The most readily interpretable data were acquired when the ice or snow surface was smooth. Detailed surface investigations on the Tanana River revealed good correlations of echo delay with solid ice depth, but an insensitivity to frazil-ice depth due to its high water content. On the Yukon River, coinciding temporalIy coherent surface and bottom reflections were associated with solid ice and smooth surfaces. AII cases of incoherent surface returns (scatter) occurred over ice rubble. Rough-surface scattering was always followed by the appearance of bottom scattering but, in many cases, including a hanging-wall formation of solid frazil ice, bottom scattering occurred beneath coherent, smooth-surface reflections. Areas of incoherent bottom scattering investigated by drilling revealed highly variable ice conditions, including frazil ice. The minimum ice thickness that could be resolved from the raw data was about 0.2 m with the 600 MHz antenna and less than 0.15 m with the 900 MHz antenna. 1

Year: 1987
DOI identifier: 10.3189/s0022143000008923
OAI identifier: oai:CiteSeerX.psu:10.1.1.429.3942
Provided by: CiteSeerX
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