Borehole location monitoring using phase-sensitive FMCW radar

Hot-water drilling is widely accepted to be the most viable method of creating deep boreholes through ice sheets rapidly and cleanly. Up to now, this process is still widely being undertaken 'blind' with little or no information made available to the drillers about the precise trajectory that a borehole is taking as it descends deeper into the ice. The negative consequences of doing this, especially when closely separated boreholes are involved, became evident after the ill-fated first attempt at drilling into Subglacial Lake Ellsworth (SLE). To help rectify this urgent need, the technological development in this project seeks to realise a novel application of phase-sensitive frequency modulated continuous wave (FMCW) radars with an active transponder, to measure from the ice surface the spatial position inside a borehole with centimetre-precision to depths of up to 3-km. It significantly builds upon the successful ApRES radar which has been recently designed and field proven for year-long, high precision measurement of Antarctic ice shelf basal melt rates.

The concept of 1D-spatial location using the proposed technique of new phase-sensitive FMCW radars with active transponders is presently at the TRL2 level, in which the basic principles have been observed and reported; and a technology concept has been formulated based on the investigators' recent work at UCL. We now aspire to carry out research to take that concept to TRL4 and validate the technology for 3D-spatial location within a laboratory and outdoor setting. Once realised, the proposed technology could ultimately increase the likelihood of success in future attempts at gaining entry into SLE and other deep (>3000-m) subglacial environments to open up new avenues of scientific exploration. The availability of such an instrument would also address the immediate needs of researchers on both the BEAMISH and CryoEgg NERC-funded projects, who are both seeking an independent method of obtaining spatio-temporal datasets at specific locations at the ice-bed interface and the broader subglacial environment, respectively. The new experimental data provided by the proposed instrument will lead to improved fundamental understanding of the dynamics occurring beneath the polar ice sheets and sustain and boost the status of UK research in these areas to internationally-leading standards.

The immediate impact of this work will be reaped by the glaciology, borehole drilling and instrumentation, and radar engineering communities. The effectiveness of that impact will be ensured by gold open access publishing of papers in appropriate high impact factor journals and making oral presentations at appropriate conferences and engaging with the media.

Specifically in terms of scientific impact, glaciologists will - by the end of this project - have access to a new, precision, prototype radar instrument for deep borehole location monitoring. This could potentially lead to generation of new spatio-temporal data of geophysical parameters within pristine subglacial environment beneath ice sheets which are of enormous scientific value. The quest to drill ever deeper through ice sheets to directly retrieve samples from these uncharted environments is presently hampered by an inability to reach these depths in a clean manner. The technology to be developed in this project will greatly assist the entire ice-drilling community, who are currently prevented from achieving this quest due to a lack of accurate information on the three-dimensional configuration of their boreholes while they are drilling. The proposed research is therefore key in maintaining the health and leading international position of other related disciplines.

The UCL and BAS press offices are actively engaged in the 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 a forum to publicise the work to young people to engage their interest in technological and science careers. We will also take advantage of outreach and media secondment opportunities available through the Royal Society. Open access publications in high impact factor journals will be authored by the investigators at UCL and BAS in conjunction with the UCL PDRA. A project website will be developed by the UCL PDRA with help from the UCL EEE 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 EEE department. The experimental work in this study will also serve as valuable case studies for the newly-launched Integrated Engineering Programme for EEE undergraduate students at UCL.