UAS-Methane: An unmanned aerial system for the remote sensing of methane flux

The goal of this proof of concept project is to develop and test an integrated new unmanned aerial system (UAS) remote sensing platform for the measurement of 3-dimensional methane concentration fields and emission flux. Our technology approach is to integrate a rotary-hovering UAS with a scanning open-path tuneable-diode-laser absorption spectrometer (TDLAS) and use it to rapidly retrieve time-evolving methane plume concentration fields over local scales (1m to 1 km). A real-time measurement and visualisation of 3D plume advection would facilitate the calculation of hotspot emission flux and serve gas-leak applications - an application relevant to NERC greenhouse-gas source apportionment science with transferability for a range of industries.

There is an urgent technological need to meet this science and impact challenge. National anthropogenic methane inventories and industrial life cycle analyses are at present a best guess of fugitive emissions extrapolated for various component source-types. Natural (biogenic) sources of methane are also poorly characterised by measurement. As agreed at the 21st Conference of the Parties (COP-21) in Paris in 2015, currently estimated anthropogenic methane inventories must now include validation by measurement to meet and monitor ambitious 2050 emissions targets.

UAS-based measurement offers an appropriate technology ripe for development for this purpose. The vertical profiling, manoeuvrability, and viewing geometry of UAS offers unique sampling for local-scale remote sensing applications and site-wide monitoring. This proposal seeks to develop such a capability from concept to prototype and builds on the team's experience in development of UAS for other environmental science applications.

UK expertise and infrastructure in the use of UAS technology for environmental science lags behind an emerging international community that promises to revolutionize understanding of local scale processes across several NERC themes (see Figure 1). We build on our experience in developing and flying in situ UAS measurement systems to develop a new remote sensing UAS TDLAS scanning technology. The project develops a new flux concept and addresses practical challenges in sensor-platform integration. The integration of TDLAS with UAS is commensurate with TRL 3/4 (non-integrated components), while data telemetry and the tomographic inversion algorithms we seek to use to derive flux from concentration measurements are all conceptual (commensurate with TRL 2). We will develop and test this integrated technology to TRL 5/6 criteria (bench test and validation) such that a working prototype platform may be ready for field trial at the conclusion of the project.

To summarise, our concept is to retrieve methane flux by remote sensing on a UAS platform. The technology to address this concept is the development an integrated UAS-TDLAS platform with a scanning gimbal. And the proof required to validate the concept will be a validated dataset, which uses tailored tomographic algorithms to invert concentration measurements for methane flux.

The new technology and concepts developed will create capacity for new directions in environmental science generally and those with specific interests in the measurement of greenhouse gases (and methane gas). It will add to a nascent national and international academic measurement community using UAS as a sampling platform. But just as importantly, this technology has transferability to a range of industrial and emergency end-users. The UK Fire Service are especially interested in our idea as a potential piece of safety equipment that could allow firemen and women to better determine safety (i.e. methane leak detection and concentration) before entering an area.

We shall ensure wide engagement and open access to our designs and concepts through data servers, websites, academic meetings, workshops and peer-reviewed journal articles. We shall also engage other potential end-users and technological developers through existing strong collaborations. To expedite this, we have already approached (or already work with) a very wide range of stakeholders; and the UK Environment Agency are formal project partners.

We have identified specific stakeholders who have expressed interest in our project. The following have expressed interest in a stakeholder workshop in the final month of our project. These comprise:

Industry: - British Petroleum Plc and other oil and gas facility operators - pipeline leak detection and emissions measurement); Cuadrilla Bowland Ltd - fugitive emissions measurement and air quality monitoring; Viridor Waste Solutions Ltd -required to monitor greenhouse gas fluxes from landfill; The Met Office - for the development of point forecasting tools and science understanding of microclimates.

Regulators and Government: UK public bodies are keen to exploit UAS potential for regulatory monitoring work (see letter of support -UK Environment Agency). Other stakeholders include the Department for Energy - tasked with GHG inventory reporting with regard to emissions targets, and DEFRA - tasked with monitoring and reporting of UK air quality.

Sensor developers: SPEC Inc., Alphasense Ltd, CrowCon Ltd, Focal Point Positioning, UAVE Ltd. Picarro Inc, Los Gatos Research Inc., Aerodyne Inc., Droplet Measurement Technologies Inc. These sensor development collaborators have worked closely with UoM academics in the past to drive sensor design in response to scientific needs and have expressed interest in developing sensors for UAS platforms for the research interests we follow in the School of Earth, Atmospheric and Environmental Science (SEAES).

Emergency Services: the UK Fire Service - interested in methane detection for safety of fire crews entering hazardous areas.

We are in contact with national and international academic partners and instrument developers through other collaborations. Our impact will be fertilised by existing lines of communication and by attendance at international conferences and workshops as this project complements many ongoing NERC projects and strategic programmes, with which we are well-integrated. These include the Greenhouse gAs Uk and Global Emissions (GAUGE) consortium, a large project tasked with the quantification of UK GHG emissions. Dr Allen is a co-PI and WP-lead for airborne measurement within GAUGE and sits on the GAUGE project management board. Co-I Hollingsworth is a partner within the Growing Autonomous Mission Management Applications (GAMMA) programme, funded by the UK Department of Business, Innovation and Skills, and Chair of AIAA's Value-Driven Design Programme Committee.

We expect our open designs to form the springboard for further and rapid development of UAS measurement platforms and drive the further adaptation of sensor technology for a wider range of science applications (beyond atmospheric), where autonomy is a key enabler.