ESA’s photosynthesis satellite fuelled

Europe's newest eye on Earth's vegetation has taken another crucial step toward orbit: ESA's FLEX satellite has been fuelled at Europe's Spaceport in French Guiana, ahead of launch on 15 September at 03:21 CEST (14 September 22:21 local time). FLEX, equipped with its Fluorescence Imaging Spectrometer, will measure the faint glow of fluorescence emitted when plants capture light for photosynthesis—a signal invisible to the naked eye that varies with environmental conditions and plant health, enabling early detection of vegetation stress before it is visible on the ground.

The stakes are high because photosynthesis underpins food production and absorbs vast amounts of carbon dioxide, yet scientists lack a full understanding of how vegetation responds to drought, heat, changing rainfall, and other stresses. FLEX will deliver the first global maps of vegetation fluorescence at 300 m × 300 m resolution, improving knowledge of how carbon moves between plants and the atmosphere and how photosynthesis drives the carbon and water cycles.

FLEX arrived in French Guiana in mid-July with the Copernicus Sentinel-3C satellite after a two-week sea voyage from Nice, France. At the spaceport, engineers have been preparing both satellites for liftoff on a Vega-C rocket. For FLEX, the fuelling milestone involved loading 30 kg of highly volatile fuel under strict safety procedures, with all non-essential personnel leaving the cleanroom. This propellant will allow FLEX to perform manoeuvres throughout its planned minimum 3.5-year mission, covering at least three seasonal vegetation cycles in both hemispheres. Launch campaign manager Frank de Bruin said preparations have gone well, and the next steps are installing FLEX on its adapter and encapsulating it in the lower position of the Vega-C fairing.