Climate change and photosynthesis: ESA Flex satellite measures changes in plant activity

Drought, climate change, pollution: you often only see harmful effects on the plant world when it is too late. A new satellite of the ESA registers changes in plant activity much earlier. And he didn't start alone. When plants carry out photosynthesis, the process in which, among other things, the oxygen that is so vital for us is produced, they emit a very weak light signal.

This fluorescence is invisible to the human eye, but it can be an important indicator of the health of the plant. World map of photosynthesis Now these signals are to be measured from space and an earth-spanning map of photosynthesis is to be created. Flex (Fluorescence Explorer) is the name of the specially designed satellite that the European Space Agency (ESA) launched into space on Tuesday. His data should help to better assess the effects of climate change and environmental stress on plant activity and the Earth's biosphere.

"Plants are exposed to various stressors," explains Thorsten Fehr, Head of the Department of Geosciences at ESA, on the sidelines of a press event at the ESOC space control center in Darmstadt. From there, the Flex mission is controlled. Green and still sick The scientist lists drought and heat, but also environmental influences, pest infestation or overfertilization. The special feature of fluorescence: It indicates changes in photosynthesis long before possible damage becomes visible.

“The plant can be beautifully green and still be stressed." So a kind of early warning system. In order to be able to measure this at an altitude of 814 kilometres, Flex has a highly sensitive device on board, the FLORIS imaging spectrometer (FLuorescence Imaging Spectrometer). It detects light radiation in the infrared range from 680 to 760 nanometers. "This light is created by the chemical processes in the plant," Fehr explains.

Smooth launch in a double pack The launch from the Kourou spaceport in French Guiana went smoothly. He expected nothing else, flirts ESOC chief Rolf Densing and praises the teams involved, but admits that most of the mission participants present had little sleep. Understandable given the start time of 3:21 am CEST. What makes this launch special: the Vega-C rocket launched two satellites.

In addition to Flex, Sentinel-3-C, another satellite from the European Commission's Copernicus Earth observation program, was also on board. A kind of cosmic carpool. With Vespa in pairs into space A Vespa adapter made it possible to accommodate both satellites in the payload bay of the Vega-C. They were exposed to space about an hour apart.

Shortly thereafter, the first signal was received on Earth, and the control center in Darmstadt took over further control. The Sentinel-3 satellites collect data on the oceans, land and ice masses, and the atmosphere. And they are an integral part of the Flex mission. Because they help to take into account the influence of temperature or clouds on fluorescence in the measurements.

Satellite tandem for better data "We want to know: What if the aerosols weren't there," explains scientist Fehr. “Or what's the temperature on the leaves? That's why we need Sentinel 3, and that's why we fly so close together." At a distance of just 40 to 100 kilometres, Flex and a Sentinel 3 satellite will fly over the earth as a tandem. This results in a time interval of six to ten seconds.

This near-simultaneity makes it possible to correctly classify the detected fluorescence values and to draw valid conclusions about the photosynthesis activity. What is photosynthesis? In photosynthesis, plants produce sugars from water and carbon dioxide (CO2). The energy source is the sunlight, which is absorbed by the green chlorophyll in the leaves.

Oxygen is separated as a "by-product". Photosynthesis therefore plays an important role in the absorption of carbon dioxide from the atmosphere. Every 27 days, the team flies over the same region and measures with an accuracy of about 300 by 300 meters. In this way, large-scale developments can be identified during the three-and-a-half-year mission.

But even then, according to Fehr, the measured values do not simply expire. "These are reference data sets that can be used for years." Drought year also in Hesse This year has shown what consequences heatwaves and dry spells can have, also for us in Hesse. "Farmers fear crop losses", "Drought is increasing in Hesse" or "Animal feed is becoming scarce in Hesse" were just a few of the headlines on hessenschau.de. So will Hessen's farmers also benefit from the Flex data?

"The data is global," says Fehr. "But with great certainty, scientists in Germany will also use them to improve the knowledge about the vegetation in the regions." This should also benefit agriculture and forestry. This would be particularly useful for Hessen's large forest population. Critical early phase In the coming days, the mission teams at ESOC will be working on the so-called Launch And Early Orbit Phase (LEOP).

The satellites are checked in detail for their condition and functionality. It is still considered critical. Thereafter, the operational operation of Sentinel-3-C will be taken over by Eumetsat, an intergovernmental operator of Earth observation satellites. It is also based in Darmstadt, not far from the ESOC.

The control of Flex remains with the ESA.