Advanced MIMO Radar Development for Geophysical Imaging Applications

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.

The principal impact of the work will be in the geophysical fluid mechanics, glaciology, polar ice, global circulation modelling and radar imaging communities. The effectiveness of that impact will be ensured by publishing papers in appropriate high-impact journals and making presentations at appropriate conferences and engaging with the media. Indeed, the Discovery Channel have already expressed an interest in this work for future programming.

Principal industrial beneficiaries are expected from within the radar community, including civil and defence companies with whom UCL is closely linked through other work. To ensure that the design strategy is consistent with future commercialisation of the radar system the UCL PDRF will make regular visits to project partners at Guidance Microwave Ltd during the project. Specific commercial interest is expected in the MIMO 2D imaging architecture, in both standard precision and phase-sensitive variants, which lends itself to other applications, such as oil exploration, where slow-moving or static targets are to be imaged by a system with minimal complexity and so there is significant potential for commercial impact of the instrument in a variety of disparate fields. A modular radar design is envisaged to facilitate deployment of future variants that can be used by the various interested communities (grounded ice sheet glaciologists, geophysicists, etc) with an integrated and cost-optimised design for the entire radar system, including power system, logger/controller, cabling and antennas.

In terms of scientific impact, fluid mechanics researchers, volcanologists and glaciologists will have access to a precision, low-cost, robust instrument easily extendable for improved depth-penetration, leading to generation of new data. Changes in ice shelves are now seen as a major influence on the contribution of the West Antarctic Ice Sheet to sea level. The technology developed during the proposed project will offer high precision 2D cross-sectional imaging through ice shelves and allow the acquisition of hitherto unobtainable medium-term time series of melt rates from some of the key ice shelves that are undergoing change, ultimately helping reduce uncertainty in sea level projections and making a major impact in this field. The radar imaging solutions developed in this work will allow the gathering of detailed experimental data to compare and inform flow laws, with the prospect of substantial academic impact accessible to both scientists and the general public. The proposed research is therefore key in maintaining the health and leading international position of other related disciplines. We will also take advantage of an outreach opportunity to promote this work during the Royal Society Summer Science Exhibition for which we have been selected to exhibit in 2012.

The UCL, University of Cambridge, University of Sheffield and BAS press offices are actively engaged in the in communication of key research results and outputs to the outside world and we will seek to use their services at any suitable opportunity. UCL makes frequent use of the Science Media Centre, based in London, who are very successful at disseminating research results to a wide, general audience. The UCL Science Lectures for schools will be used as a forum to publicise the work to young people to engage their interest in technological and science careers. Publications in high-impact factor journals will be authored by the PIs at UCL, Cambridge and Sheffield in conjunction with the UCL PDRA. A project web-site will be developed by the UCL PDRA with help from the UCL EE system support team who are experienced in this area. One or two MSc projects may be associated with the work, with appropriate training provided by means of specialised MSc courses (such as Radar Systems and Antennas & Propagation) run in the UCL EE Dept.