Advanced Technology for Radar Sounding of Polar Ice

该奖项由极地计划办公室提供，为极地仪器和技术开发计划提供资金，以开发用于研究极地冰盖的先进冰穿透机载雷达系统。自20世纪60年代末问世以来，雷达探测已成为冰川学工作中最重要的技术，也是冰下地质研究的一个重要方面。在20世纪70年代，丹麦技术大学（TUD）设计并建造了一种基于当时最先进技术的冰层穿透雷达。这个古老的系统负责收集南极洲和格陵兰冰盖上绝大多数的冰探测数据。这台雷达被德克萨斯大学升级为数字记录，并在20世纪90年代在南极洲西部和东部进行了广泛的冰厚度分辨率调查。目前，已经确定了雷达冰探测能力的三个进步类别。要在冰川学和冰川地球物理学研究的前沿问题上取得科学进展，就必须取得这些进展。这些类别是：1）改进了冰柱穿透，以探测穿过厚冰和/或暖冰以及穿过高度非均匀冰的冰下界面; 2）改进了内层空间分辨率，并改进了深层探测; 3）表征冰下界面的能力，具体而言，确定水的存在。最近对火星古环境的兴趣和对木星上可能有冰覆盖的海洋的认识，卫星促进了陆地冰川学界内外在冰下探测和定性问题方面的研究活动。这一活动的高潮是设计了一种新的探冰雷达，作为探测行星冰体的试验台。喷气推进实验室开发了一个原型（并在堪萨斯大学的帮助下建造），它利用了现代雷达技术的最佳技术。在格陵兰岛和南极洲的JPL/KU系统的实地测试表明，这种新的雷达有可能解决冰川地球物理研究前沿的基本问题。从上述三类所需进展的角度来看，这些实地测试也揭示了当前原型的一些局限性。该项目将通过合并JPL/KU雷达与UT/TUD雷达的组件来克服这些缺点。这种新的“多机构雷达探测器”（MIRS）的目标是通过脉冲压缩（相对于当前的UT/TUD雷达）提高层分辨率和总系统灵敏度，并通过保留回波波形的完整形状（幅度和相位）沿着自动校准总系统灵敏度来实现检测界面的材料/粗糙度表征。该系统的另一个好处是提高了“看穿”高度分散的冰的能力，例如冰流边缘或山谷冰川附近的裂缝区域。为了验证系统设计并充分建立MIRS的能力，这项开发工作将包括针对各种冰盖环境的现场测试，包括假设的和已建立的冰下水体下最厚的部分东南极冰盖。这将通过在2001/2002年南极考察季节进行一系列机载雷达调查来完成。

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.