Finnish Meteorological Institute helps ESA yield information about photosynthesis from space

Photosynthesis drives plant growth and plays a central role in the exchange of carbon between the land and the atmosphere. ESA’s Fluorescence Explorer (FLEX) mission will measure solar-induced chlorophyll fluorescence, or SIF – a very weak glow emitted by plants when they absorb sunlight and closely linked to photosynthetic activity.

While satellites have monitored the extent and greenness of vegetation for decades, FLEX will provide information more directly related to how plants are functioning. Its FLORIS instrument will measure vegetation fluorescence in much greater detail, complemented by observations from the Sentinel-3 satellite which will fly in tandem with FLEX.

Finnish Meteorological Institute helps separate the vegetation signal from the atmospheric contribution

Measuring plant fluorescence from space is challenging because the weak signal from plants is hidden within the Earth’s atmospheric contribution. Earth’s atmosphere changes, and so does the light we observe from the satellite.

“It's a bit like trying to spot a distant candle in daylight: the plant signal is very faint compared to all the sunlight. Our task is to characterize these atmospheric effects accurately so that reliable information about vegetation and photosynthetic activity can be derived from the observations,” says Neus Sabater, Senior Scientist at the Finnish Meteorological Institute.

Over several years of ESA project work, the Finnish Meteorological Institute has developed methods for characterizing atmospheric effects and separating them from the signal originating at the Earth’s surface. This atmospheric correction is essential for deriving accurate estimates of vegetation fluorescence and photosynthetic activity from FLEX observations.

The Finnish Meteorological Institute will also contribute to validating FLEX observations once the satellite becomes operational. The Sodankylä Supersite in northern Finland, jointly developed by ESA and the Finnish Meteorological Institute for satellite calibration and validation, will provide independent ground-based reference measurements.

New information on vegetation and the carbon cycle

More accurate observations of photosynthetic activity can improve understanding of how vegetation responds to drought, heat and other environmental stresses. The observations are relevant to research on climate change, the carbon cycle, ecosystem health and food production.

FLEX can also improve understanding of how much carbon terrestrial ecosystems take up from the atmosphere and support the development and evaluation of climate and carbon-cycle models. This can help scientists understand both how vegetation responds to a changing climate and how it influences the climate through the carbon cycle.