Swath Measurements of Ice Sheet Bottom Topography and Radar Reflectivity
Abstract
Ice sheet thickness is a fundamental measurement for understanding the dynamics of large ice sheets (terrestrial or extraterrestrial). Radar is the primary tool used to measure ice thickness but a major challenge is accurately measuring the arrival time of the basal echo in the presence of surface clutter, which may arise from processes such as wind driven deposition and erosion or crevassing. Essentially, the basal echo strength, which is weak because of attenuation through the ice, becomes comparable to the surface scattering signal even though the coincident surface return comes from a large, off-nadir angle. During the past 4 years, we explored three surface clutter rejection techniques and applied them to data collected with 150/450 MHz radars operated from aircraft over the Greenland Ice Sheet. We also investigated how the techniques could be used to go beyond nadir sounding of ice sheets and, when operated used with broad-beam antennas, could successfully acquire 3-dimensional intensity images of the ice sheet base. In this paper, we describe experiments to image the ice sheet base using: synthetic aperture radar (SAR) interferogram filtering; SAR tomography; and beam steering. For the case of a broad beam antenna array, we show that interferograms filtering provides the highest quality topographic data from both the left and right sides of the aircraft but only under optimal conditions. We show that a beam-steering/radar tomography hybrid algorithm provides the most robust topography and also yields an intensity map. We provide example topographies for the base of the Greenland Ice Sheet and suggest how the approach could be used for future sounding of extraterrestrial ice. The research described in this paper was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under a grant from the National Aeronautics and Space Administration. 3-d radar image of the base of the ice sheet. Scene is an orthorectified mosaic located just south of the main Jacobshavn Drainage Channel
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFMED23A0547F
- Keywords:
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- 0726 CRYOSPHERE / Ice sheets;
- 6982 RADIO SCIENCE / Tomography and imaging