Fraunhofer IOF Team Delivers Optical Assembly for Emissions Monitoring Mission

A team of researchers led by the Fraunhofer Institute for Applied Optics and Precision Engineering IOF (Fraunhofer IOF) have delivered an optical assembly for the spectrometers on board the satellites for the European Space Agency (ESA)’s Copernicus Anthropogenic Carbon Dioxide Monitoring (CO2M) mission. Starting in 2026, the mission will use a constellation of satellites equipped with IR spectrometers to carry out high-resolution spectral measurements of atmospheric CO₂ to accurately map emissions from cities, countries, and large industrial areas.

Fraunhofer IOF researchers delivered the disperser instrument, which consists of two prisms and a grating. According to Thomas Höing, project manager at Fraunhofer IOF, the apparatus very precisely splits the light reflected from Earth into its spectral colors to enable high-precision measurements of CO₂ content in Earth's atmosphere. The CO2M satellites will be able to determine the carbon dioxide content of Earth's atmosphere at any location on the planet with an accuracy of <100 CO₂ particles per billion molecules of air. Combined with a high spatial resolution, the satellites can analyze on a global level very precisely in which region and by which sources the most emissions are released.

“The nanostructured gratings have a particularly high efficiency of more than 90% and a low degree of polarization of less than 10%,” Höing said, of the disperser's principal components. Further, said Stefan Risse, head of Fraunhofer IOF’s Department of Precision Optical Components and Systems, the gratings design features grating grooves that are filled with a highly refractive material. The grooves are then interlayer-free, Risse said, and a covalent bonding process is used to join the gratings to the prisms. “Additively manufactured lightweight housings, various coatings and a light-scattering surface roughened with a laser also serve to minimize stray light. In this way, the spectrometer's signal-to-noise ratio is optimized,” Risse said.

A disperser element delivered by a team from Fraunhofer IOF to the European Space Agency's Copernicus Anthropogenic Carbon Dioxide Monitoring (CO2M) mission the light reflected from the earth, using a sophisticated optical design. Shown here is the disperser for the SWIR 2 channel. Courtesy of Fraunhofer IOF.

The CO2M mission is part of the European Copernicus program. It is one of six extension missions developed to expand the Earth observation capabilities of the Copernicus program. The series of missions is being implemented by ESA on behalf of the European Union.