Sentinel-4 spectrometer

Sentinel-4 provides air quality observations every 60 minutes covering Europe and part of north Africa.

The UVN instrument is an ‘imaging spectrometer’: it takes images of the scene below the satellite. For each image pixel the instrument acquires a spectrum that resolves the colour (or wavelength) of the incoming light.

To see in colour, the human eye relies on three types of cone cells. The Sentinel-4 UVN instrument, however, can distinguish between around 1000 more colours than the human eye.

It measures solar light reflected by Earth in the ultraviolet, visible and near infrared, in the following bands: ultraviolet (305–400 nm), visible (400–500 nm), and near-infrared (750 –775 nm).

The video shows how the mirror mechanism works to scan Earth’s atmosphere to provide critical data on the composition of the atmosphere at a spatial resolution of 8 km x 8 km.

Sentinel-4 scanner
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The Sentinel-4 mission is the latest in a long line of spectrometers to measure atmospheric properties from space. They include:

• the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) instrument on ESA’s Envisat mission, which operated between 2002 and 2012, and measured atmospheric trace gases.

• the Global Ozone Monitoring Experiment (GOME) on ESA’s ERS-2 satellite, which operated between 1995 and 2011, and the GOME-2 instruments on the MetOp series of satellites, launched in 2006, 2012 and 2018.

• the Ozone Monitoring Instrument on NASA’s Aura.

• the Tropospheric Ozone Monitoring instrument on the Copernicus Sentinel-5P satellite, which provide air quality data.