Sentinel-5A is an advanced imaging spectrometer embarked on the first MetOp Second Generation (MetOp-SG-A1) weather satellite, launched into polar orbit in August 2025.
Another two Sentinel-5 spectrometers, Sentinel-5C and Sentinel-5D, will be launched later, one on MetOp-SG-A2 and one on MetOp-SG-A3, ensuring more than 20 years of operational life for the Sentinel-5 mission.
ESA's Sentinel-5 Mission Scientist, Ben Veihelmann, said, "Sentinel-5 is a very powerful European mission to observe our atmosphere. With its long mission lifetime, Sentinel-5 will be instrumental for monitoring greenhouse gases, ozone layer recovery, and air pollution trends."
The Sentinel-5 mission provides observations of key air pollutants, essential climate variables, and stratospheric ozone-the protective layer shielding life on Earth from harmful ultraviolet radiation.
From an altitude of 832 km in a polar sun-synchronous orbit, Sentinel-5 captures comprehensive data across the entire globe each day. It complements the Sentinel-4 mission, which observes Europe and North Africa hourly from geostationary orbit.
The Sentinel-5 mission's high-resolution imaging spectrometer operates across seven spectral bands spanning the ultraviolet, visible, near-infrared, and shortwave infrared ranges to measure a host of trace gases, including ozone, nitrogen dioxide, sulphur dioxide, formaldehyde, glyoxal, carbon monoxide, and methane, as well as aerosols and UV index.
Sentinel-5A is still in its commissioning phase, but this initial dataset offers a strong indication of what's to come.
Heinrich Bovensmann, from the University of Bremen, noted, "It is exciting to see that an idea we have been working on for more than a decade has come to life."
Ozone plays a dual role in Earth's atmosphere: while stratospheric ozone shields life from harmful UV radiation, ground-level ozone is a harmful air pollutant that affects human health and ecosystems. Observations show the hole in stratospheric ozone above Antarctica remains visible, with column density values falling below 220 Dobson Units. Although ozone-depleting substances were banned under the Montreal Protocol in 1989, their long atmospheric lifetime means recovery has been gradual. Evidence of improvement has begun to appear in recent years. Sentinel-5's measurements will help track the ongoing recovery of this vital protective layer.
Measurements of nitrogen dioxide over the Middle East reveal higher concentrations around major cities and industrial sites such as refineries, power stations, and smelters. Elevated concentrations are also evident over the densely populated Nile Valley in Egypt. Similar data for South Africa highlight strong emissions in the Highveld region, likely resulting from coal-fired power stations.
Nitrogen dioxide is a major air pollutant produced primarily by human activities such as traffic, power generation, industrial processes, cooking, and heating. Cloud cover can obscure parts of these observations, reducing surface visibility.
Data on formaldehyde show elevated concentrations along the northwestern coast of Angola linked to wildfire emissions, while enhanced levels over the Central African Republic result from a mix of fire activity and biogenic sources. Formaldehyde is a carcinogenic air pollutant, and the current dataset is considered preliminary, with further refinements expected to reduce biases caused by partial cloud cover.
A separate dataset revealed a strong sulphur dioxide plume emitted from the Klyuchevskaya Volcano in Russia's Kamchatka Peninsula, one of the most active volcanoes in the world.
ESA's Sentinel-5 Project Manager, Didier Martin, said, "We are extremely pleased to see these first preliminary results, and I would like to thank everyone involved in making this mission a success. Most importantly, the results confirm that the Sentinel-5A imaging spectrometer is performing well, with calibration and data processing progressing as planned. This puts the mission firmly on track to support scientific research, air-quality and UV health alerts, and the monitoring of essential climate variables-ultimately delivering benefits for citizens, the environment, and the economy alike."
ESA's Director of Earth Observation Programmes, Simonetta Cheli, added, "Developed by the European Space Agency for Copernicus, the Earth observation component of the European Union's space programme, Sentinel-5 will play a key role in safeguarding our planet."
Related Links
European Space Agency
Earth Observation News - Suppiliers, Technology and Application
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