| Status | In development |
| Launch | 2025 |
| Space organisation | ESA |
| Type | UV / visible / NIR / SWIR (270 – 2385 nm) |
| Orbit | Geocentric (835 km altitude) |
| SRON contribution | Sentinel-5 |
Daily global coverage
To keep track of how human and natural activities affect the Earth’s atmosphere, it is necessary to monitor it. Daily global monitoring is only possible from space. While TROPOMI has been taking care of this since 2017, Sentinel-5 assures us of this long-term overview. Between 2025 and 2039, three copies will be launched one after another, at intervals of about eight years.
Gases in the atmosphere
Sentinel-5 monitors the gases nitrogen dioxide, ozone, sulfur dioxide, carbon monoxide and methane, among others. The latter is the second most important greenhouse gas after CO2, and one-third responsible for global warming. The largest methane leaks have a climate impact comparable to the order of magnitude of total Dutch traffic. Sentinel-5 tracks these anywhere in the world within a day at most, as long as cloud cover allows. Carbon monoxide is an air pollutant and an important indicator of CO2 emissions. In fact, CO2 emissions are often accompanied by carbon monoxide emissions. CO2 is more difficult to measure because there is much more of it in the atmosphere, so there is little contrast. For carbon monoxide, this is not true.
United Nations and CAMS
Every week, our scientists publish a world map of all major methane sources based on TROPOMI. Sentinel-5 will continue to do this until 2046. That data goes to the United Nations and the Copernicus Atmospheric Monitoring Service (CAMS). The United Nations then alerts responsible governments and companies to their emissions. They do this, for example, through their Methane Alert and Response System. After several months, they publish information on measured emissions, which gives the responsible party time to fix the problem.
Spectrometer
Sentinel-5 is a spectrometer sensitive to ultraviolet, visible light, near-infrared and short-wave infrared (SWIR). In that wavelength range are the main fingerprints of the substances nitrogen dioxide, ozone, sulfur dioxide, carbon monoxide and methane. As sunlight reflects off the Earth’s surface, it makes its way back through the atmosphere, on its way to Sentinel-5. The above gases then leave their fingerprints in sunlight by absorbing specific colors. This creates a barcode of black lines in the spectrum measured by the instrument.
Immersed grating
SRON has developed an “immersed grating” for the SWIR detector, which measures methane and carbon monoxide, among other things. A grating breaks down incident sunlight into colors to create a spectrum. SRON engineers have etched lines into a silicon disk-a wafer-that behave like a lattice in such a compact manner. To redirect the incoming light even more strongly, this “recessed lattice” is pressed onto a silicon prism. This grating-prism combination disperses the colors more strongly than a conventional grating, making the instrument more compact. SRON developed an earlier version of a recessed grating for the TROPOMI instrument on the Sentinel-5p satellite in the 2010s. That one consists of one part, in which the grating is recessed directly into the prism.
