The new Copernicus Sentinel-4 satellite mission has achieved its goal, sending its first set of visual data to Earth. These first high-resolution images, acquired from geostationary orbit, highlight atmospheric concentrations of pollutants such as sulfur dioxide, ozone and, above all, nitrogen dioxide. Based on initial measurements from October 8, 2025, the maps show clear “hot spots” of tropospheric nitrogen dioxide along the Mediterranean coast and, particularly clearly, over the Po Valley.
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Sentinel-4, the geostationary eye for air quality
The provision of these first images by Sentinel-4 is an achievement. This new instrument, positioned in geostationary orbit 36,000 kilometers above Earth on 1 July, is destined to become one of the pillars of Europe’s capacity to monitor air quality in near real time. The initial images clearly reveal the atmospheric concentrations of several critical pollutants, providing information for their environmental and health management.
Nitrogen dioxide: sources and risks
The focus is in particular on precisely tracked nitrogen dioxide (NO2), a major air pollutant. It is released in large quantities following the combustion of fossil fuels, a process that occurs daily in various sources, such as vehicle engines, power plants and heating systems. Its concentrations, in line with the nature of the emission sources, can vary extremely rapidly.
Nitrogen dioxide is not only toxic in itself, but is also a key precursor for the formation of secondary pollutants. In fact, it contributes to the genesis of ozone at ground level and particulate matter. Both of these secondary formations are known to have serious repercussions on human health and the environment, exacerbating respiratory problems and general ecological impacts.
Although the current dataset is still preliminary, these first acquisitions from Sentinel-4 represent a real milestone for Europe. The ability to continuously monitor the composition of the atmosphere from geostationary orbit will provide essential tools to better understand the evolution of pollution and implement more effective mitigation strategies.
