The European Space Agency (ESA) just took a courageous leap forward in air quality monitoring. In July of 2025, they launched Sentinel-4, a major step forward in this vital discipline. This groundbreaking small satellite is hosted on the ESA-supported first Meteosat Third Generation Sounder satellite. It does this from a geostationary orbit, 36,000 kilometers above Earth. From this unique vantage point, Sentinel-4 will have an uninterrupted view over Europe and northern Africa. It has become essential for measuring and predicting air pollution.
Sentinel-4 uses an ultraviolet–visible–near-infrared spectrometer to detect solar light reflected by Earth’s surface and atmosphere. It’s especially great at distinguishing spectral signatures, or “fingerprints,” of trace gases and aerosols in the atmosphere. This new, stunning capability opens up a wealth of unprecedented insights into pollutants. Although the satellite is still in its commissioning phase, early results look very encouraging.
Initial Findings and Observations
The first images from Sentinel-4 reveal tropospheric nitrogen dioxide concentrations, showcasing distinct pollution hotspots along the Mediterranean coast and over Italy’s Po Valley. The space-based satellite quickly and effectively captures rapid changes in air pollution, including these unprecedented shifts due to COVID-19. For example, just this week it captured a plume rising from Italy’s Mount Etna that wafted southeastward over the Mediterranean Sea.
ESA’s Sentinel-4 Project Manager, Didier Martin, said that he was thrilled by these first preliminary results.
“We are extremely happy to see these first preliminary results, and my thanks go to everyone involved in the mission.” – Didier Martin
Beyond marking the pollutants, the data provided by Sentinel-4 shows the widespread distribution of particulate matter, nitrogen dioxide, and sulfur dioxide in the air. Our calculations confirmed that the Western Balkan countries and Greece have the highest level of pollutant concentration. By comparison, the Baltic Sea region demonstrates a floor. This type of granular, hyper-localized data serves as the foundation for developing meaningful solutions to air quality issues in communities nationwide.
“Firstly, and arguably most importantly, they confirm that Sentinel-4 is healthy, and that the calibration and the data processing chains are on track. This essentially means that it is well on the road to becoming Europe’s first mission dedicated to delivering hourly measurements of air pollutants across the continent.” – Didier Martin
Sentinel-4’s mission is extremely important, as it will drastically improve air quality monitoring and modeling. Its hourly measurements upend the status quo in how we measure air quality. This new capability has a huge, positive impact on air quality forecasting throughout Europe. This new capability will enable more timely responses to episodic air pollution events—which is increasingly important given their immediate and sometimes dire impacts on public health.
The Impact on Air Quality Forecasting
ESA’s Director of Earth Observation Programs, Simonetta Cheli, highlighted the collaborative effort that brought Sentinel-4 to fruition:
Sentinel-4’s ability to detect rapid changes in air pollution will offer essential input for pollution forecasting models. This information will be invaluable to policymakers and public health officials working to develop strategies to mitigate air pollution’s impact on communities.
“We are very proud to contribute to this important mission, together with our key partners—the European Commission and Eumetsat, and our dedicated industrial teams. It truly demonstrates the power of collaboration.” – Simonetta Cheli
With Sentinel-4 finishing its commissioning phase, users from all sectors are looking forward to its full operational capabilities. The satellite’s data processing chains are the longest lead items. This progress provides the foundation for a rich understanding of air quality patterns and trends across Europe.
“The mission is still in its commissioning phase, but these first results clearly show that everything is functioning well. These initial glimpses are extremely encouraging.” – Simonetta Cheli
ESA’s Sentinel-4 Mission Scientist, Ben Veihelmann, remarked on the transformative potential of this satellite:
Future Prospects and Developments
With technology and data collection methods quickly evolving at a rapid pace. Therefore, Sentinel-4 will be key in curbing air pollution worldwide. Its enhanced monitoring capabilities will empower scientists and researchers to devise more effective strategies for improving air quality across Europe.
ESA’s Sentinel-4 Mission Scientist, Ben Veihelmann, remarked on the transformative potential of this satellite:
“Sentinel-4 is the first European mission that will deliver hourly air-quality observations. By capturing fast changes in air pollution, Sentinel-4 is a game-changer for monitoring and forecasting air quality over Europe.” – Ben Veihelmann
With ongoing advancements in technology and data collection methods, Sentinel-4 is set to become an essential tool in combating air pollution. Its enhanced monitoring capabilities will empower scientists and researchers to devise more effective strategies for improving air quality across Europe.