Calibrated pCO2 in air and surface ocean Sensor for ASVs (CaPASOS)

Department Name: Science and Technology


The human emission of carbon dioxide, largely from fossil fuel burning, will continue for the foreseeable future to be the most important cause of climate change. Only about half of our emissions are remaining in the atmosphere however. The other half is being absorbed, it is believed, in approximately equal amounts by vegetation on land and uptake by the ocean. These "natural sinks" of CO2 are consequently of huge value to us, since they slow the progress of climate change, so their present operation, and possible changes future uptake of CO2, are a focus of intense research. The sink of CO2 into the ocean is today being observed by measurements of atmospheric and sea surface pCO2, the partial pressure of CO2 at the surface of the ocean. This controls the rate at which CO2 exchanges between the ocean and atmosphere, and which for this reason has been designated an "essential ocean variable" by the Global Ocean Observing System. These observations are usually made from commercial vessels, and where there are busy shipping routes, for example in much of the Atlantic and North Pacific Oceans, there are sufficient observations to describe the air-sea flux. However, there are other very large regions (the Indian, South Pacific and Southern Oceans for example) where we have woefully insufficient data.

In the future, this need could be met by autonomous surface vehicles (ASVs) making pCO2 measurements, and our proposal is to develop a pCO2 sensor specifically designed for ASVs. It will follow protocols that have been established by international bodies for the highest quality measurements suited to calculating the air-sea flux of carbon dioxide in the open ocean. The technical challenge is to adapt the successful principles of the instruments mounted in ships or on large buoys, where space and power are not limiting factors, to achieve the same high accuracy with small space and power footprint, resistance to violent motion, and long endurance, necessary on an ASV. We will achieve this by bringing together the extensive experience that the Exeter University group has in operating ship-based CO2 systems over 20 years, with improvements in engineering, utilising the experience and expertise of the NOC Technology and Engineering groups. We will use the basic measurement technique that has been well tested on the large instruments (equilibration of water with gas, and measurement of CO2 in gas by non-dispersive infra-red detection). However, we will use miniaturised components having small volumes and low flow rates of gas, enabling even a small instrument to carry on-board calibration gases. The specifications of the final instrument will include: endurance of up to a year and with frequency of measurements (both surface water and atmosphere) sufficient to define daily cycles, regular calibration using on-board calibration gases stored in miniature compressed gas cylinders, and measurement of CO2 in dried air which has equilibrated with surface water by direct contact. The instrument will also conform to data standards and integration protocols to enable the ready integration and exchange of sensors into autonomous platforms.

A laboratory prototype exists, built by U. Exeter. To achieve our main objective, our sub-objectives are: 1) Development of second generation and deployment alongside a shipboard instrument and testing at coastal sites (2) modification and deployment on a mooring at the Western Channel Observatory for an extended period (3) Construction of third generation with attention to each component of the system to optimise performance and robustness, (4) integration into an ASV, (5) extensive sea testing (e.g. on the "MASSMO" exercises, experimental missions of autonomous marine vehicles conducted regularly around UK waters, and on research cruises.

Planned Impact

The societal and economic impacts of the project will include, in the short to medium term the production of a product, "CaPASOS" which will be ready for licensing or other commercialisation route within 1 year of the end of the project. Product launch is expected to occur in 2021-22 with conservative expected sales exceeding 30 units by year 2 and a total 5 years sales total of 200 units (CAG of 30%). This will deliver jobs and income for the UK even if licensing is chosen over company launch, and the licensing company is non-UK, as it will stimulate services and measurement capability in the UK, and will return license income to the inventors and their institutions. We have interest in the potential commercialisation of the product from partners RS Aqua, illustrating a healthy engagement from the commercial sector. CaPASOS will be deployable on a wide range of USV MAS platforms, and will therefore support the growth of MAS observation systems. This will stimulate economic activity (e.g. business for MAS platform, sensors, systems and services companies). In the medium to longer term, the data returned from widespread CaPASOS enabled MAS will provide data directly to carbon flux assessments and data bases, particularly in areas where there are significant data gaps. This data will also inform biogeochemical models and process studies. This understanding will improve our knowledge of the ocean carbon sink and biogeochemical processes with impact on the UK's and global management of climate change and marine resources. Therefore this data will assist evidence based decision by decision makers to manage the oceans and climate change.


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Description This project has developed new prototype sensor for measuring carbon dioxide in water and the atmosphere at the surface of the ocean. This enables the amount of carbon dioxide being taken up by the oceans to be measured, even from small autonomous surface vessels (robot ships). The also enables study the effects of climate and environmental change on natural processes and the carbonate (carbon dioxide in water) system to be studied without needing to collect samples and take them to a laboratory for analysis. We have integrated and applied these sensors in autonomous vehicles which enables more data to be collected in both space and time as well as reducing cost, and carbon expended for each measurement point.
Exploitation Route The sensors developed, and the integration with autonomous vehicles can be used by the wider marine science and offshore industry sectors to measure and understand changes in water chemistry.
Sectors Aerospace

Defence and Marine


Food and Drink


Digital/Communication/Information Technologies (including Software)





Democracy and Justice


including Industrial Biotechology

Description GEORGE - Next generation multiplatform Ocean observing technologies for research infrastructures
Amount € 9,997,437 (EUR)
Funding ID 101094716 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 01/2023 
End 06/2027
Description MISSION (Mid- Infrared Silicon Photonic Sensors for Healthcare and Environmental Monitoring)
Amount £5,757,814 (GBP)
Funding ID EP/V047663/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 06/2021 
End 06/2026