Advanced MIMO Radar Development for Geophysical Imaging Applications

在世界范围内，物质流动是一种重大的自然灾害，但我们预测其行为和规划其影响的能力有限，部分原因是我们缺乏对其流动动力学的理解和缺乏详细的实验数据，特别是地下运动的实验数据。同样，极地冰架耗竭，特别是在南极洲，是气候变化和海平面上升的一个重要和日益增加的因素，但很难用常规技术轻易测量。这项研究涉及伦敦大学学院的电子工程师和谢菲尔德大学的地球物理学家之间的合作，旨在开发和部署一种复杂的、通用的、模块化的相控阵雷达系统，该系统能够通过穿透粉末云形成雪崩中密集流的详细的二维或三维图像，这是使用光学仪器无法实现的。该技术还可以通过南极冰架进行毫米精度的横断面成像，以监测季节或年份期间的变化，特别是基底层深度的变化。这将提供宝贵的新实验数据，以了解在质量运动流动情况下的流动规律和在冰架监测情况下控制海洋环流及其对冰架耗竭影响的模式。目前，在雪崩中，光电仪器只能提供密集流中单点的流量信息。对于火山碎屑密度流等其他流，几乎没有可用的数据。在我们最近的合作之前，用于雪崩和斯特龙堡火山喷发的多普勒雷达提供了流速的粗略图像，平均超过50米，只给出了流速大小的总体测量（没有方向信息）。我们的仪器将平均距离缩短到只有1米，因此，第一次可以获得流动中单个块的信息，并根据它们对整体流动动力学的重要性进行评估。此外，将采用MIMO相控阵方法，该方法将提供1度的高方位角分辨率，以产生这些流的距离和方位角分辨率，为该领域的研究人员提供丰富的新数据。对于南极冰架成像，由于距离大，卫星雷达成像无法提供高精度的冰架深度估计，而且目前没有精确的便携式探地雷达仪器可用，这是通过UCL最近开发的相敏FMCW处理技术来解决的，该技术将采用冰架内部特征的毫米分辨率，包括基底层，并具有二维截面成像能力。这将在此应用程序中产生无与伦比的清晰度和精度的数据。这些仪器提供的新实验数据将使这些过程的模型得到改进，方法是将系数限制在合理的值之内，或许还会完全摒弃某些已提出的规律，从而对地球物理质量流和海洋环流对冰架耗竭的影响进行更精确的模拟。反过来，这将改进风险分析以及防御结构的效果和设计。这项研究的预期结果将大大提高我们对流动运动和极地冰架枯竭的理解，并维持和提高英国在这些领域的研究地位，使其达到国际领先水平。

Mass movement flows are a significant natural hazard throughout the world and yet our ability to predict their behaviour and plan for their effects is limited, in part, by our lack of understanding of their flow dynamics and lack of detailed experimental data, particularly of sub-surface movements. Similarly, polar ice shelf depletion, particularly in Antarctica, is a significant and increasing contributor to climate change and sea level rise, but is difficult to readily measure with conventional techniques.This research, involving collaboration between electronic engineers at UCL and geophysicists at the University of Sheffield, aims to develop and deploy a sophisticated, versatile, modular phased array radar system that is able to form detailed 2 or 3 dimensional images of the dense flow in snow avalanches, by penetrating the powder cloud, which is not possible using optical instruments. This technology can also perform mm-precision cross-sectional imaging through antarctic ice shelves to monitor changes, in the basal layer depth in particular, over periods of seasons or years. This will provide invaluable new experimental data to inform the flow laws in the case of mass movement flows and models governing ocean circulation and its impact on ice shelf depletion in the case of ice shelf monitoring.At present in snow avalanches, opto-electronic instruments can provide flow information at a single point in the dense flow only. For other flows such as pyroclastic density currents there are almost no data available. Prior to our recent collaboration, Doppler radar for snow avalanches and Strombolian eruptions provided crude images of the flow speed, averaged over 50 m and only giving an overall measure of the velocity magnitude (with no information on direction). Our instrument reduces the averaging distance to only 1 m so that, for the first time, information on individual blocks in the flow can be obtained and assessed in relation to their significance for the overall flow dynamics. In addition, a MIMO phased array approach will be adopted that will provide high azimuth resolution, of the order of 1 degree, to yield both range and azimuth resolution of these flows, providing a wealth of new data for researchers in this area. For Antarctic ice shelf imaging, satellite radar imaging is unable to offer high precision estimates of ice shelf depth due to the large stand-off distance, and no precision portable ground penetrating radar instruments are currently available This is addressed by means of a phase-sensitive FMCW processing technique recently developed at UCL will be adopted to provide mm-resolution of features within the ice shelf, including the basal layer, and with a 2D cross-sectional imaging capability. This will produce data of unrivalled clarity and precision in this application.The new experimental data provided by these instruments will lead to improved models for these processes by constraining the coefficients to reasonable values and perhaps rejecting some proposed laws outright, resulting in more accurate modelling of geophysical mass flows and of the influence of ocean circulation in ice shelf depletion. In turn, this will improve risk analyses and the effect and design of defensive structures. The expected outcome of this study will considerably improve our understanding of flow movement and polar ice shelf depletion and sustain and boost the status of UK research in these areas to internationally-leading standards.