Summary
ESA’s FLEX Earth Explorer satellite and the Copernicus Sentinel-3C satellite have reached orbit after launching together on a Vega-C rocket from French Guiana. FLEX will measure plant fluorescence linked to photosynthesis, while Sentinel-3C will extend monitoring of oceans, land, ice and the atmosphere.
ESA’s FLEX Earth Explorer satellite and the Copernicus Sentinel-3C satellite have been launched together aboard a Vega-C rocket from Europe’s Spaceport in French Guiana. The launch took place on 15 September 2026 at 03:21 CEST, or 14 September at 22:21 local time.
The mission, designated Vega-C flight VV30, placed the two Earth-observation spacecraft into their required orbits. After separate deployments, ESA’s European Space Operations Centre received the first signal from each satellite, confirming that both had been released safely and had established contact with ground control.
One launch, two Earth-observation missions
A new launch adapter called Vespa enabled the satellites to be stacked inside Vega-C’s fairing. Sentinel-3C was positioned on top and injected into orbit first, followed by FLEX approximately one hour later.
The arrangement demonstrates Vega-C’s ability to deploy two Earth-observation missions with different orbital requirements on a single flight. The rocket can place up to 2,300 kg into low-Earth orbit. It uses three solid-propellant stages before a fourth, liquid-propellant stage performs the precise final placement of satellites.
FLEX is ESA’s first satellite designed specifically to measure photosynthetic activity from space. Its Fluorescence Imaging Spectrometer will detect the extremely faint fluorescence emitted by plants as they absorb sunlight during photosynthesis. This signal is invisible to the human eye. In biological terms, photosynthesis uses light energy to help plants convert carbon dioxide and water into chemical energy; the fluorescence measured by FLEX provides an indication of how efficiently vegetation is performing that process.
The resulting observations are intended to help scientists assess plant health and ecosystem productivity, as well as examine how vegetation responds to environmental stress and climate change. FLEX was developed within ESA’s FutureEO programme as a research mission.
Sentinel-3C is the third satellite in the Copernicus Sentinel-3 series. Its instruments will continue systematic observations of oceans, land, ice and the atmosphere, including ocean and land-surface temperatures, ocean colour, sea and ice conditions, vegetation and inland-water levels.
The mission is designed to provide near-real-time information for ocean forecasting, climate monitoring, environmental management and scientific research. Sentinel-3C forms part of Copernicus, the Earth-observation component of the European Union’s Space programme.
Combining fluorescence with environmental measurements
The two missions will contribute different types of information. FLEX will measure the faint light associated directly with photosynthetic activity, while Sentinel-3 observations will provide environmental context, including clouds, aerosols, water vapour, land-surface temperature, land-cover type and additional vegetation parameters.
Initially, FLEX will orbit in tandem with Sentinel-3A. Later, Sentinel-3C will be moved to replace Sentinel-3A in that formation. Flying in tandem will allow FLEX measurements to be combined with near-simultaneous Sentinel-3 observations, helping scientists relate plant activity to atmospheric and surface conditions.
ESA says this combination will provide a more detailed view of the health and functioning of vegetation around the world than either type of measurement could provide alone.
Both satellites have now entered the launch and early orbit phase. Mission controllers will spend the next stage checking spacecraft health and performance and confirming that the systems are functioning as expected. After commissioning, Eumetsat will assume responsibility for routine Sentinel-3C spacecraft operations and the delivery of marine and near-real-time atmospheric data, while ESA will continue to control FLEX and provide Sentinel-3 land, cryosphere, inland-water and offline atmospheric products.