Space

Sentinel-5A: first images of ozone and air pollution

The mission provides observations of key air pollutants, essential climate variables and stratospheric ozone, the protective layer that shields life on Earth from harmful ultraviolet radiation

by Davide Madeddu

27 November 2025

3' min read

Translated by AI

Versione italiana

3' min read

Translated by AI

Versione italiana

From the ozone hole to nitrogen dioxide over the Middle East and South Africa, continuing with formaldehyde over parts of Africa to sulphur dioxide emissions from an active volcano in Russia.

These are the first images sent by the Copernicus Sentinel-5A satellite, an advanced imaging spectrometer, embarked on the first second-generation MetOp meteorological satellite (MetOp-SG-A1), launched into polar orbit in August 2025 to map gases and air pollutants as part of the European Commission and European Space Agency's Copernicus Earth observation programme.

The images were released at the Esa Ministerial Conference in Bremen. The mission provides observations of key air pollutants, essential climate variables and stratospheric ozone, the protective layer that shields life on Earth from harmful ultraviolet radiation. "Due to its long lifetime," emphasises Ben Veihelmann, ESA mission scientist, Sentinel-5 will be crucial for monitoring greenhouse gases, ozone layer recovery and air pollution trends."

The global ozone map

The first image of a global ozone map was acquired on 13 October. "The hole in the stratospheric ozone layer over Antarctica is clearly visible, with column density values of less than 220 Dobson Units," Esa emphasised in a note. "Although the use of ozone-depleting substances, such as halogenated hydrocarbons, was banned by the Montreal Protocol in 1989, their long persistence in the atmosphere means that the complete recovery of the ozone layer has been gradual. Evidence of this recovery has only begun to appear in recent years.

The Sentinel-5 observations will expand and strengthen the long-term record of ozone monitoring, helping scientists to monitor the continued recovery of this vital protective layer'.

Nitrogen dioxide

A second image "shows the vertical column density of nitrogen dioxide on 13 October 2025 over the Middle East, where higher concentrations are visible around major cities and above oil and gas refineries, power plants and smelters".

'High concentrations are also evident over the densely populated Nile Valley in Egypt,' Esa further points out. 'The third image also shows nitrogen dioxide on 13 October 2025, but over South Africa. High concentrations are visible in the Highveld region, probably due to coil power plants'.

Then there is a fourth image showing the density of the vertical column of formaldehyde on 13 October 2025. 'Elevated concentrations along the northwest coast of Angola are related to emissions from forest fires,' Esa further writes, 'while higher levels over the Central African Republic result from a combination of fire activity and biogenic emissions.

There are two more images on the roll call: one showing a 'sulphur dioxide plume' emitted by the Klyuchevskaya volcano on the Kamchatka peninsula in the far east of Russia.

'It is one of the most active volcanoes in the world, with more than 50 eruptions since 1700, and is characterised by smoke rising continuously above its summit,' it further reads. The last image presents data on the Earth's radiance from 5 to 6 October 2025. The map shows landmasses, oceans and clouds and was mainly used to check the health of the satellite instrument in flight'.

Two more Sentinel-5 spectrometers, Sentinel-5A and Sentinel-5B, will be launched in the future. "We are very proud to contribute to this important mission, working closely with our key partners: the European Commission, Eumetsat and our dedicated industrial teams," stresses Simonetta Cheli, Director of ESA's Earth Observation Programmes. This result really highlights the power of collaboration. The mission is still in the commissioning phase, but these first results clearly show that everything is working well. These first insights are extremely encouraging. We look forward to Copernicus Sentinel-5 becoming fully operational in the coming months".