Carbon dioxide (CO2) is a main driver of the anthropogenic greenhouse effect in the Earth’s atmosphere. In the 2015 Paris agreement, the world community reached a consensus to limit global warming to 2°C above preindustrial values. Four years later, in 2019, this was substantiated for Europe by the European Green Deal. One key element within the Paris Agreement is the global stock take which is foreseen every five years, starting in 2023, to assess the progress towards the ambitious reduction goals. This requires a reliable global observation system in order to independently monitor CO2 emissions on a global scale. The EU’s planned CO2M (Copernicus Anthropogenic Carbon Dioxide Monitoring) mission will be a core component for assessing the efficiency of the mitigation measures. CO2M shall map CO2 emissions from anthropogenic sources globally on regional or national scales.
About 30% of the current CO2 emissions from fossil sources originate from coal-fired power plants. The retirement of such facilities in Europe is offset by increasing capacities in China and India. Planned satellite missions like CO2M will be able to detect about a quarter of these emissions, namely those from the largest power plants. A recent study from the Institute of Atmospheric Physics now shows that DLR’s demonstrator mission CO2Image would be able to detect 90% of the emissions.
CO2Image is currently in mission phase A, competing with another payload. Scientists from several DLR institutes (Atmospheric Physics, Optical Sensor Systems, Remote Sensing Technology) are working in close collaboration with the University of Heidelberg to integrate the sensor system into the satellite bus “CompactSat”, whose development is led by the DLR institute of Space Systems.
While the proposed concept of the instrument is based on technologies similar to other greenhouse gas missions, the strategy of the mission is complementary. CO2Image is solely dedicated to the survey of localized sources like coal-fired power plants. The sensor is based on a grating spectrometer with comparatively low spectral resolution, which in turn offers high spatial resolution. With a footprint of down to ~50m on the ground, this system has a key advantage for detecting emissions from CO2 point sources: excess concentrations per ground pixel are much higher, because the CO2 signal is averaged over a smaller area and therefore much easier to measure.
If finally selected, CO2Image is scheduled for a launch in 2024 or 2026. Accompanying the European CO2M mission, CO2Image shall provide zooming capabilities to allow for a closer look at emissions from coal-fired power plants. After successful demonstration of the mission concept, this compact and cost-efficient instrument design could be deployed as secondary payload or in constellations of smallsats, making an important step towards the independent monitoring of CO2 emissions in the future, helping to control the efficiency of the pursued mitigation measures.
Left: Global distribution of estimated annual CO2 emissions from power plants (CARMA database). Right: Cumulative distribution of the emissions shown on the left panel. About 64% of the CO2 emissions are from medium-sized power plants (1-10Mt per year). (Graphics: Strandgren et al.)