Europe is preparing to launch a new satellite
Diana Parkhouse, Unsplash
Sentinel-4, Europe's first geostationary air quality monitoring mission, will be launched in 2025 as part of the Copernicus programme. The satellite will provide hourly high-resolution data on the concentrations of key pollutants such as ozone (O₃), nitrogen dioxide (NO₂), formaldehyde (HCHO) and sulphur dioxide (SO₂). This will be a significant step forward in atmospheric tracking and emission forecasting, supporting EU environmental policy and measures to reduce public health risks.
Air pollution remains one of the most pressing environmental and societal problems in Europe. According to the WHO, it causes around 600,000 premature deaths in Europe each year. In major cities such as Milan, PM10 levels often exceed safe limits, forcing residents to wear masks. Eastern Europe has also seen pollution thresholds regularly exceeded, sparking public protests. Major sources of pollution include transport, industrial emissions and the burning of fossil fuels. Natural factors such as sandstorms and forest fires also exacerbate the situation by adding fine particles and smoke to the atmosphere.
Unlike previous satellites, Sentinel-4 will be geostationary, allowing it to update data hourly throughout daylight hours across Europe. This will ensure continuous monitoring of diurnal changes in air quality, including peak-hour emission spikes, industrial emissions and transboundary transport of pollutants.
The satellite will be based on the MTG-S (Meteosat Third Generation - Sounder) and will be equipped with an ultraviolet visible near infrared (UVN) spectrometer capable of measuring ozone, nitrogen dioxide, formaldehyde, sulphur dioxide and aerosols with high accuracy. Sentinel-4 will work in conjunction with the Infrared Sounder (IRS) to provide synchronised monitoring of meteorological and atmospheric data.
Most current air quality monitoring systems in Europe rely on ground stations and polar-orbiting satellites, which provide only a few images per day. This makes it difficult to track fast-changing phenomena such as peak-hour emissions or transboundary pollution.
Sentinel-4 will provide hourly updates in real time, which will enable rapid response to pollution spikes and timely inform the public about declining air quality. It will also help in decision-making on urban planning, traffic management and industrial emissions control.
Sentinel-4 will be an important tool to support European air quality and pollution reduction policies. The EU Ambient Air Directive sets legally binding limits for pollutants such as nitrogen dioxide (NO₂), sulphur dioxide (SO₂) and particulate matter (PM10, PM2.5). However, monitoring compliance with these standards remains a challenge, especially in regions with high industrialisation and heavy traffic.
Sentinel-4 will provide continuous and standardised data tracking to help identify pollution hotspots, improve forecast accuracy and take timely action to reduce emissions. The satellite will also support the Zero Pollution Action Plan, which aims to reduce pollution-related deaths by 55 per cent by 2030.
Sentinel-4 is scheduled for launch in the summer of 2025. The satellite will work in conjunction with MTG-S (Meteosat Third Generation - Sounder) to provide synchronised monitoring of atmospheric and meteorological data. After launch, the satellite will provide hourly data on air pollution in Europe, helping to shape better environmental policies and ensure public health.
