PARIS, 20 September 2026 — Europe has placed two new Earth-observation satellites into orbit, including the first ESA mission designed specifically to measure photosynthetic activity from space. FLEX and Copernicus Sentinel-3C launched together on 15 September and both established contact with mission control after deployment.
What launched on Vega-C?
A Vega-C rocket lifted off from Europe’s Spaceport in French Guiana at 03:21 CEST on 15 September. The launcher released Sentinel-3C first and FLEX about an hour later into its required orbit. ESA’s operations centre in Germany received the first signals from both spacecraft, confirming safe separation and initial contact.
The successful launch begins—not completes—the missions. Controllers must now commission the spacecraft and instruments before routine science and operational data can flow.
What will FLEX actually measure?
FLEX, short for Fluorescence Explorer, will detect the extremely faint light emitted by plants during photosynthesis. That fluorescence is invisible to human eyes but changes with plant condition and environmental stress. ESA says the measurements should give researchers a more direct view of how efficiently vegetation converts sunlight and carbon dioxide into energy.
The mission is designed to improve understanding of plant health, ecosystem productivity and the movement of carbon and water between vegetation and the atmosphere. It does not diagnose individual crops or predict harvests on its own.
What does Sentinel-3C add?
Sentinel-3C is the third spacecraft in the Sentinel-3 series for Copernicus, the European Union’s Earth-observation programme. Its instruments will measure ocean and land-surface temperatures, ocean colour, sea and ice conditions, vegetation, inland-water levels and atmospheric properties. The wider series supports ocean forecasting, climate monitoring, environmental management and research.
Why will the satellites work in tandem?
FLEX will initially orbit in tandem with Sentinel-3A. Later, Sentinel-3C is due to replace Sentinel-3A in that formation. Near-simultaneous Sentinel observations can describe clouds, aerosols, water vapour, land cover and surface temperature around the same areas where FLEX detects plant fluorescence. Combining the datasets should help scientists separate a plant signal from atmospheric and surface effects.
When will useful data become available?
ESA has not presented first contact as the start of an instant public service. The launch-and-early-orbit phase checks spacecraft health, followed by instrument commissioning and data validation. Sentinel-3C will ultimately be operated by Eumetsat for routine marine and near-real-time atmospheric products, while ESA will remain responsible for FLEX. Researchers should wait for calibrated releases before drawing conclusions from the new measurements.
Primary sources: ESA’s launch report; ESA’s FLEX mission page.
Illustrative image: Photo by Dan Meyers on Unsplash. Reporting basis: official material available on 20 September 2026.