Accession Number : ADA295072
Title : Detection of Crevasses Near McMurdo Station, Antarctica with Airborne Short-Pulse Radar.
Descriptive Note : Special rept.,
Corporate Author : COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
Personal Author(s) : Delaney, Allan J. ; Arcone, Steven A.
PDF Url : ADA295072
Report Date : MAR 1995
Pagination or Media Count : 19
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 5-1 (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.
Descriptors : *AIRBORNE, *RADAR, *SHORT PULSES, VELOCITY, CONTROL, STATIONS, TOOLS, SNOW, FEASIBILITY STUDIES, HELICOPTERS, ICE, SURFACE PROPERTIES, FLIGHT, SURVEYS, GLOBAL POSITIONING SYSTEM, DATA ACQUISITION, COMMERCIAL EQUIPMENT, AURORAE, DATA RATE, DISTORTION, RECONNAISSANCE, ISLANDS, BRIDGES, CONSTRUCTION MATERIALS, ANTARCTIC REGIONS, GLACIERS, ROSS SEA.
Subject Categories : Aerodynamics
Distribution Statement : APPROVED FOR PUBLIC RELEASE