The upcoming Copernicus Sentinel-4 mission, scheduled for launch no earlier than July 2025, is set to mark a turning point in air quality monitoring across Europe and northern Africa.
Orbiting from a fixed geostationary position 36,000 km above Earth, Sentinel-4 will deliver hourly, high-resolution data on key air pollutants – offering an unprecedented look into the rapidly changing dynamics of our atmosphere.
Unlike its predecessors, Sentinel-4 won’t just offer daily snapshots. Instead, it will provide real-time tracking of pollutants such as nitrogen dioxide, ozone, and other harmful trace gases that fluctuate quickly due to traffic, industrial activity, and weather patterns.
This shift to hourly updates is being hailed as a breakthrough in air quality forecasting, enabling faster, more accurate responses to pollution events.
“Sentinel-4 is a complete game changer for air quality forecasting.” – Ben Veihelmann, Sentinel-4 and Sentinel-5 Mission Scientist at ESA.
Why orbit location matters
Sentinel-4 is unique in that it will operate from a geostationary orbit, enabling continuous surveillance of the same region.
Unlike satellites in low-Earth orbit that only pass over the same location once per day, Sentinel-4 will maintain a constant view of Europe and parts of northern Africa.
This orbit allows the satellite to scan its target region every hour, capturing the fast-moving changes in air pollution driven by human activity and meteorological conditions.
This ability to detect hourly fluctuations is critical for understanding the transport and transformation of pollutants and will be a game-changer for short-term air quality forecasts and public health advisories.
Advanced technology for trace gas detection
At the heart of the mission is a highly sophisticated UVN (ultraviolet, visible, near-infrared) imaging spectrometer capable of detecting minute concentrations of harmful gases and aerosols.
By analysing sunlight that has passed through the atmosphere or reflected off Earth’s surface, Sentinel-4 can identify the spectral “fingerprints” of pollutants and determine their concentrations.
This data will help track the vertical distribution of substances like ozone and sulphur dioxide, offering insights not just into ground-level pollution but also into how pollutants behave throughout the atmosphere.
International collaboration for global impact
The Sentinel-4 mission is a joint effort between the European Space Agency (ESA) and Eumetsat, the European Organisation for the Exploitation of Meteorological Satellites.
Sentinel-4’s instrument will be mounted on the Meteosat Third Generation Sounder (MTG-S), a weather satellite, combining two missions into one platform and maximising efficiency.
The mission is also part of a global air quality monitoring initiative from space. Together with NASA’s TEMPO (for North America) and South Korea’s GEMS (for Asia), Sentinel-4 will contribute to a constellation of geostationary satellites that collectively provide near-continuous coverage of the most densely populated areas in the northern hemisphere.
This international coordination is crucial, as air pollution does not respect national borders.
Turning air quality data into actionable insights
All data generated by Sentinel-4 will be openly accessible and free to use, supporting a wide range of services and stakeholders.
Among the main beneficiaries will be the Copernicus Atmosphere Monitoring Service (CAMS) and the Copernicus Climate Change Service, both of which will integrate the data into operational models and forecasts.
This information will help public agencies issue timely air quality alerts, verify compliance with environmental regulations, and assess progress toward emissions reduction goals.
Beyond governance, Sentinel-4 data will aid scientific research, support the solar power industry, and even inform aviation decisions by tracking volcanic emissions.
Enhancing public health and policy
One of the mission’s most significant impacts will be in the field of public health.
By providing detailed, timely information on pollution levels, Sentinel-4 will help protect vulnerable populations – such as people with respiratory conditions – by enabling health warnings and exposure reduction strategies.
The satellite’s data will also serve policymakers by informing evidence-based decisions and tracking the effectiveness of environmental legislation.
It represents a crucial step in translating scientific capability into real-world action, fostering healthier, more resilient communities.
A game-changer in air quality monitoring
With its advanced instrumentation, unique orbital position, and collaborative foundation, the Sentinel-4 mission promises to redefine the landscape of air quality monitoring.
By offering high-frequency, high-resolution data on atmospheric pollutants it will enhance our understanding of air pollution and strengthen our ability to combat it.
As Europe prepares for the satellite’s launch in mid-2025, anticipation is building within the scientific, environmental, and public health communities.
Sentinel-4 is not just another satellite – it is a powerful tool to help us breathe easier in the years to come.
