MicroCarb satellite tracks carbon dioxide from space
If you have ever looked at a climate promise and wondered how anyone checks it, MicroCarb is part of the answer. The UK Space Agency says the satellite is the first European mission built to characterise greenhouse gas fluxes at Earth’s surface and to estimate how much carbon is being absorbed by oceans and forests, the planet’s two biggest natural sinks. MicroCarb is a joint mission between the French space agency CNES and the UK Space Agency. It launched in July 2025 and released its first images in September 2025. Since then, teams have been fine-tuning calibration and data-processing algorithms, which is a useful reminder that a launch is only the beginning; a satellite also has to learn how to read Earth well.
To see why this matters, it helps to slow the story down. Carbon dioxide is one of the greenhouse gases that traps heat in the atmosphere. Some carbon is released by natural processes, and much more is added by human activity such as burning fossil fuels. At the same time, forests and oceans absorb part of that carbon. **What this means:** climate change is not only about how much CO2 we produce. It is also about how much of it stays in the air, how much is taken in by the natural world, and how those patterns change over time. Better measurements give us a clearer starting point.
According to the government case study, MicroCarb adds to earlier CO2 missions and will join an international network of greenhouse gas satellites. Its job is not simply to gather more numbers, but to gather more precise ones. That helps scientists improve maps of the carbon cycle and separate natural absorption from emissions linked to people, industry and transport. That precision also matters politically. Countries signed up to the Paris Agreement to limit global surface warming, but targets only mean something if the data behind them can be checked. A mission like MicroCarb helps us compare what is being promised with what the atmosphere is actually showing.
One of the most practical parts of the mission is its city-scan mode. MicroCarb can map atmospheric CO2 over cities, which could give local leaders better evidence when they are planning housing, transport, heating systems or greener public spaces. When people talk about smart cities, this is the sort of information that can make the phrase mean something real. The wider value goes beyond town halls. Watching greenhouse gas patterns more closely should help us judge how forests, coastlines, farms and communities may respond to a warming planet, and where action to cut damage could make the biggest difference.
MicroCarb circles Earth at an altitude of 650km and repeats its observation cycle every 21 days. On board is an infrared spectrometer that measures oxygen and carbon dioxide in sunlight reflected from Earth. The instrument looks at four spectral bands: 0.76μm, 1.27μm, 1.6μm and 2μm. If that sounds technical, here is the simple version. Different gases leave different fingerprints in light. By reading those fingerprints very carefully, the satellite can work out how much O2 and CO2 are present in the air above a given place.
The mission is also built for very fine measurement. CO2 concentrations are expected to be measured at around 1 part per million, with a pixel size of 4.5 by 9km. In its city-scanning mode, resolution tightens to 2 by 2 square kilometres. That does not mean the satellite can see every chimney or traffic jam, but it does mean it can pick up patterns at a scale cities can use. MicroCarb will also retrieve Solar Induced Fluorescence, often shortened to SIF. This is a signal linked to photosynthetic activity, so it gives scientists another way to judge how actively plants are taking in carbon. **Why you should care:** a greener-looking area is not always a stronger carbon sink, and SIF helps tell the difference.
The UK has put £15 million into the mission, and that funding has given British scientists and companies a strong role in the work. The UK Space Agency says Thales Alenia Space UK handled assembly, integration and testing at STFC RAL Space in Harwell, Oxfordshire, while STFC RAL Space designed the pointing and calibration system that lets MicroCarb take measurements at chosen locations. Other parts of the project sit with the National Physical Laboratory, which provided the ground calibration facility and is helping develop algorithms and quality checks. Professor Paul Palmer, working through the National Centre for Earth Observation and the University of Edinburgh, is turning CO2 observations into maps of carbon absorption and emissions. Dr Rob Parker is part of the NCEO team delivering the mission’s SIF retrieval algorithm, drawing on work from the University of Leicester, while GMV UK is helping build and assure the processing systems behind several CO2 data products.
All of this points to a simple lesson. Climate reporting is often treated as a story of arguments, targets and political rows, but it is also a story about measurement. Before we can judge whether a policy is working, or whether a city is cutting emissions, we need trusted evidence. MicroCarb will not stop global warming on its own. What it can do is give us a sharper picture of where carbon is coming from, where it is being absorbed, and how quickly those balances are shifting. For students, teachers and anyone trying to read climate news more carefully, that makes this satellite worth watching.