From Space to Shore. Tracing Ship Emissions to Their Source

By Jean Joy, Earth Observation Consultant, Satellite Applications Catapult

Satellites can now see pollution from ships across Europe’s busiest shipping lanes. The question that regulators and business want to understand is which ship caused it. Ships carry more than 80% of world trade by volume and produce around 3% of global greenhouse gas emissions according to UNCTAD’s Review of Maritime Transport,¹ along with nitrogen oxides and sulphur dioxide that affect air quality in port cities. To mitigate the impact caused by these emissions, the International Maritime Organization (IMO) has set industry a target of net zero by or around 2050, with cuts of at least 20% by 2030 and 70% by 2040 against 2008 levels.²

Those targets now come with a price. Since 2024, shipping companies have had to buy allowances under the EU Emissions Trading System for voyages to and from European ports,³ and since July 2026 the UK scheme has also covered domestic shipping over 5,000 gross tonnage and above.⁴ When emissions cost money, independent evidence of where they come from is worth paying for. That is a commercial opportunity for UK companies that can supply that evidence from space.

On 23 September, Satellite Applications Catapult hosted a webinar with speakers from the European Space Agency (ESA), Spanish space technology group GMV, Ocean OS, GHGSat, the French climate research laboratory LSCE (Laboratoire des Sciences du Climat et de l’Environnement) and Science Partners Research Cooperative. They presented two projects that tackle the problem from opposite ends. EO4SEM (Earth Observation for Ship Emission Monitoring), funded by ESA and led by GMV, is testing whether satellites can measure ship emissions across European waters reliably enough to support regulation. EMMA, a UK project led by Ocean OS, works at the scale of a single port, combining satellite data, ship tracking and sensors on shore to work out which vessels are behind pollution events in Plymouth Sound. Between them, they cover the chain from spotting emissions at sea to evidence a port or regulator can act on.

From Pilot to Paying Customer

Together, the two projects show the chain taking shape. More data from new missions, methods that a European regulator is helping to test, and UK software that turns observations into evidence for a single port. The next step is proving it works well enough for customers to pay for it. EMMA’s next phase will test how reliable its matches are, with more validation, longer data records and additional satellite sources. EO4SEM will continue its work with EMSA towards routine monitoring of shipping emissions in Europe.

Satellite data can track emissions along shipping routes, in ports and around the coast. ©EO4SEM – Geospatial Explorer

Estimates Are Not Evidence

Most shipping emissions figures are estimates. They are calculated from ship movements, engine types and fuel models, and depend on what operators report. These methods are essential, but they carry uncertainty and are hard to verify independently. Once emissions carry a price, that uncertainty costs business money.

Satellites offer a second, independent source of evidence. They measure pollutants and greenhouse gases across open sea, shipping lanes and ports. Combined with ship tracking, weather data and atmospheric models, they show where emissions occur and, increasingly, which ships they came from. That lets ports, regulators and operators check reported figures against what is in the air.

More Data are on the Way

Opening the webinar, Antony Delavois of ESA explained why ESA backs projects such as EO4SEM: to turn satellite data into evidence that environmental policy can rely on. Two new Copernicus missions launched in 2025 will add hourly pollution monitoring over Europe and daily global coverage. Copernicus’ data sets are free to use, so each new mission gives UK companies more raw material for commercial services.

From Shipping Lanes to a Single Port

EO4SEM is testing whether satellites can track nitrogen oxides, carbon dioxide and methane from shipping well enough to support EU regulation, and the European Maritime Safety Agency (EMSA) is helping to test the method. Today’s instruments can already map emissions along Europe’s main shipping lanes, but their pixels are kilometres across: fine for a shipping lane, too coarse to tell one ship from another in a crowded port.

EMMA works at the other end of the chain. Led by Ocean OS with Satellite Applications Catapult, B4T Group and the University of Plymouth, it uses Plymouth Sound as a testbed to work out which vessels are behind pollution events. The University of Plymouth describes the goal as a weather forecast for maritime emissions.

Closing the Resolution Gap

That leaves the hardest part. Spotting raised pollution levels is one thing. Proving which ship caused them is another, and it is the answer ports and regulators will pay for.

Satellite Applications Catapult is testing whether Sentinel-2, a satellite built to map land in pixels tens of metres across, can pick out nitrogen dioxide plumes in a busy port, and is feeding the results into EMMA as another line of evidence. Satellite data alone cannot prove which ship caused a pollution event. Combined with ship tracking, weather data and ground sensors, they narrow the field. That is the first step towards evidence that can stand up in a compliance check.

Sentinel-2 processing shows how higher-resolution observations could help identify emission sources. (Contains modified Copernicus Sentinel data 2025, processed by SAC.)

Ocean OS: Turning Evidence into a Product

This is where the pieces come together. Ocean OS’s platform combines satellite data, ship movements, weather, air-quality readings and atmospheric modelling. Using machine learning and source-apportionment techniques, it estimates which maritime activities are most likely behind a pollution event, and how confident it is in each match.

For a port, that means knowing which ships are behind pollution spikes near the waterfront. For a regulator, it is a way to check reported emissions and for an operator, it is evidence of compliance.

Satellite Applications Catapult is a technical partner in EMMA. We help UK companies such as Ocean OS test their services with real users and find routes to market. Jean leads the Earth observation strand of EMMA at the Satellite Applications Catapult, using satellite data to detect ship emissions around UK ports. Their work adapts and validates published nitrogen dioxide detection methods, with early demonstration work at Plymouth Sound.

Work with us. If you run a port, regulate shipping or operate ships and want to test what this evidence could do for you, contact Catapult’s Mission Intervention Manager, Sarah Cheesbrough at sarah.cheesbrough@sa.catapult.org.uk. If you are a UK company with maritime emissions data or analytics, we would like to hear from you too.

Missed the webinar? Watch the full recording to hear from ESA, GMV, GHGSat, Ocean OS and the other speakers.

References

1. UNCTAD (2023) Review of Maritime Transport 2023: Towards a green and just transition. Geneva: United Nations.

2. International Maritime Organization (2023) 2023 IMO Strategy on Reduction of GHG Emissions from Ships.

3. European Commission, Reducing emissions from the shipping sector.

4. UK ETS Authority, UK ETS scope expansion: domestic maritime – main Authority response. GOV.UK.

5. Varon, D. J. et al. (2024) Quantifying NOx point sources with Landsat and Sentinel-2 satellite observations of NO2 plumes. Proceedings of the National Academy of Sciences (PNAS).