Evaluation and Demonstration of Gravity Gradiometers

QinetiQ Ltd, Imperial College and the University of Oxford will jointly investigate the use of novel gravity gradiometers to detect buried objects such as pipes, tunnels and sinkholes. We will model the gravitational field of a range of buried targets, and investigate methods to mitigate noise and clutter. We will determine what type of objects are detectable, at what range, and develop some outline Concepts of Operation. We will investigate the applicability of a range of sensors, both high performance "cold atom fountains" and lower-cost MEMS-based devices, configured as gravity gradiometers, and compare them to the performance of commercially available sensors. We will build a single-axis gravity gradiometer based on two existing gravimeters, and use this to validate our models with through short field trials to demonstrate the detection of a buried object.

Economic benefits:
Four million holes are dug in British roads every year, 300,000 of them in London alone. 36% of London traffic delays caused by roadworks, with a total cost to London business is not far short of £1 billion. This is likely to be replicated in cities across the country. According to some estimates, half the holes dug by the water industry are in the wrong place. The ability to sense a buried pipe before starting to dig would greatly reduce unnecessary disruption.
A major benefit of this research will be to inform the National Quantum Programme of expected targets and detection ranges using gravity gradiometers based on the published performance of a range of gravity sensors, including ones being developed by the National Quantum Programme. This information is likely to help guide the parties involved in the development of their devices.

Social impacts:
The UK does not have a sovereign capability in full-tensor gravity gradiometry. The classical-technology Lockheed Martin FTG instrument is ITAR-controlled, and can only be used for a very strictly controlled set of applications. This work would pave the way towards a sovereign capability which could be used for both commercial and military applications without ITAR restrictions.

Environmental impacts:
Stand-off detection of buried objects will have a positive environmental impact, as it will allow remote sensing as opposed to physical investigation and inspection.
Earth and planetary science: though deployment of gradiometers in Earth orbit is being pursued separately with Thales-Alenia UK, some of the technical challenges will require similar approaches. We would therefore anticipate cross benefits from this project to Earth and planetary gravity measurements using compact gradiometers. Such measurements aim to quantify on Earth the effects of climate change through ice-sheet loss and aquifer degradation.

Regional impacts:
Remote detection of dense smuggled material at borders/ports would potentially not only increase security but also reduce delays, supporting the freer movement of goods.