Advanced Technology for Radar Sounding of Polar Ice

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AbstractThis award, provided by the Office of Polar Programs, provides funds from the Polar Instrumentation and Technology Development Program to develop an advanced ice-penetrating airborne radar system for studying polar ice sheets. Since its inception in the late 1960's, radar sounding has distinguished itself as perhaps the single most important technique for glaciological work and an important aspect of sub-ice geological research. In the 1970's The Technical University of Denmark (TUD) designed and constructed an ice-penetrating radar based on, then, state-of-the-art technology. This now venerable system is responsible for the vast majority of all ice sounding data yet collected over the ice caps of Antarctica and Greenland. This same radar was upgraded for digital recording by The University of Texas and used for extensive ice-thickness-resolution surveys in both West and East Antarctica conducted during the 1990's. Currently, three categories for advances in radar ice sounding capability have been identified. These advances are required to achieve scientific progress on several problems at the forefront of glaciological and glacio-geophysical research. These categories are: 1) improved ice column penetration for detection of the subglacial interface through thick and/or warm ice and through highly heterogeneous ice; 2) improved internal layer spatial resolution and improved deep layer detection; 3) the ability to characterize the subglacial interface and, specifically, to identify the presence of water.Recent interest in the Martian paeleoenvironment and the recognition of possible ice covered oceans on the Jovian satellites has stimulated research activity in sub-ice detection and characterization problems from both within and outside the terrestrial glaciological community. This activity has culminated in a new design for an ice penetrating radar that is a test-bed for sounding of planetary ice bodies. A prototype was developed by the Jet Propulsion Laboratory (and constructed with the assistance of The University of Kansas) that draws on the best of modern radar technology. Field tests of this JPL/KU system in both Greenland and Antarctica indicate that this new radar has the potential for addressing fundamental questions at the forefront of glacio-geophysical research.From the perspective of the three categories of needed advances outlined above, these field tests have also revealed some limitations with the current prototype. This project will work to overcome these shortcomings by merging components of the JPL/KU radar with the UT/TUD radar. The objectives for this new "Multi-Institutional Radar Sounder" (MIRS) are to improve layer resolution and total system sensitivity through pulse compression (relative to the current UT/TUD radar), and to enable material/roughness characterization of the detected interfaces by preserving the complete shape (both magnitude and phase) of the echo waveform along with automatically calibrating the overall system sensitivity. An additional benefit of this system will be the improved ability to "see through" highly scattering ice such as the crevassed regions near ice stream margins or in valley glaciers.In order to verify system design and fully establish the capabilities the MIRS, this development work will include field tests that target a wide range of ice sheet environments, including both hypothesized and established subglacial water bodies underlying the thickest portions of the East Antarctic Ice Sheet. This will be accomplished with a series of airborne radar surveys to be conducted during the 2001/02 Antarctic field season.