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|Detection of crevasses near McMurdo Station, Antarctia with airborne short-pulse radar
|National Science Foundation (U.S.)
Delaney, Allan J.
Arcone, Steven A.
Ross Ice Shelf
|Cold Regions Research and Engineering Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
|Special report (Cold Regions Research and Engineering Laboratory (U.S.)) ; 95-7.
Abstract: Airborne short-pulse radar is evaluated experimentally as a rapid reconnaissance tool for locating snow-bridged crevasses. An immediate need for a crevasse detector is present within the U.S. Antarctic Program, which is planning a major surface traverse from McMurdo to deliver construction materials to South Pole Station. This feasibility study of a crevasse detection system was performed near McMurdo Station, Antarctica, in January 1994. The radar utilized pulses centered near 200 and 500 MHz and was operated from a low flying helicopter with altitude and speed as variables. A global positioning system (GPS) was used for survey control. Results are presented over glacial ice on Ross Island and at various locations on the Ross Ice Shelf near white and Black Islands and near the Aurora Glacier terminus. These studies include a control line along which crevasse width and snow-bridge thickness were measured, transects along which crevasses were apparent, and also where crevasses were expected, but were not apparent. Strong evidence of crevassing was recorded at flight speeds near 20 m s⁻¹ (45 mph), at altitudes near 15 m, and at a data acquisition rate of 51 scans/second. Crevasses are detected by the reflections and diffractions from distorted layering in snow bridges, and by the strong diffractions from within the crevasses. The strongest diffractions apparently emanated from within the crevasse and not from the base of the snow bridge. Along the control line, a crevasse with no surface expression was detected by radar and verified by probing and digging. Transects devoid of crevasses show layering without the small scale distortion seen over snow bridges. Future plans are to use data acquisition rates of 160 scans/second, available with commercial equipment, to allow a survey speed of about 64 m s⁻¹ (140mph). We believe that quality data could then be acquired at altitudes up to about 30 m, making short pulse radar a useful crevasse mapping tool from fixed wing aircraft.
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