This animation shows how the Copernicus Sentinel-4 ultraviolet, visible, and near-infrared (UVN) spectrometer, mounted on the Meteosat Third Generation Sounder satellite (MTG-S1), is able to observe nitrogen dioxide over Europe and northern Africa (NO2 data kindly provided by CAMS).

Nitrogen dioxide is a trace gas that forms in our atmosphere when fossil fuels are burned.

The UVN spectrometer, on board MTG-S1, orbits Earth in a geostationary orbit. It is the first mission to monitor European air quality from this orbit, which means it maintains its position – at 36 000 km from Earth’s surface – over the equator as the Earth rotates. 

The instrument measures sunlight reflected by Earth’s surface and atmosphere, as well as light arriving both directly from the Sun. When light passes through the atmosphere, trace gases leave a signature, or ‘fingerprint’, on the light arriving at the satellite. These signatures are resolved by the UVN spectrometer and are exploited to estimate the amount of the trace gases present in the atmosphere.