Sentinel-3C and FLEX satellites launch to study Earth

Two European satellites with major UK contributions have successfully launched into orbit. They will monitor the planet’s health and better understand climate change

Sentinel-3C and the European Space Agency’s FLEX (FLuorescence EXplorer) mission launched together aboard a Vega-C rocket from the European Spaceport in French Guiana at 2:21 am UK time on 15 September 2026.

A new view of the planet

Sentinel-3C is the latest addition to the European Union’s Copernicus Earth observation program. The satellite will monitor key features of Earth’s land and oceans, including sea and land surface temperatures, ocean and land color, and sea surface topography.

The Sentinel-3 satellites provide data for a wide range of applications, from weather and ocean forecasting to wildfire detection and water quality monitoring.

One example is the monitoring of algal blooms. By observing changes in ocean color, Sentinel-3 can help scientists detect and track blooms that can harm marine ecosystems, contaminate seafood, and affect coastal water and air quality.

The satellite will also help monitor extreme weather events. Sentinel-3 observations have already been used to assess land surface temperatures during heatwaves, providing information that can help authorities understand the effects of extreme heat.

Measuring the health of plants

FLEX has a different focus. The mission is designed to study vegetation by detecting the faint fluorescence plants emit during photosynthesis.

This light provides scientists with information about how efficiently plants convert sunlight into energy. It can also reveal how vegetation responds to environmental stresses such as heat, drought and disease.

The information could improve understanding of how ecosystems respond to a changing climate and provide valuable data for areas such as agriculture, food security, and environmental management.

FLEX will operate in tandem with Sentinel-3C, allowing data from the two missions to be combined. While FLEX measures plant photosynthesis directly, Sentinel-3C provides information about atmospheric conditions, temperature and the surrounding land surface.

UK expertise behind both missions

The UK has played an important role in developing both satellites.

For FLEX, Thales Alenia Space UK completed assembly, integration and testing of the satellite platform in Belfast. Other UK companies also contributed, including Teledyne e2v, which supplied detector hardware for the FLORIS instrument, ABSL, which provided spacecraft batteries, and Nammo Westcott, which supplied propulsion hardware.

UK expertise also contributed to Sentinel-3C. Scientists and engineers at STFC RAL Space and Airbus Defense and Space helped design and develop the Sea and Land Surface Temperature Radiometer.

Teledyne e2v and ABSL also contributed hardware to the Sentinel-3C mission.

Continuing long-term Earth observation

Sentinel-3C joins Sentinel-3A and Sentinel-3B, which launched in 2016 and 2018 respectively. Sentinel-3C is expected to eventually replace Sentinel-3A, while Sentinel-3D is planned for launch in 2028.

Maintaining this sequence of satellites is important because scientists need consistent, long-term observations to identify environmental trends and understand how the planet is changing.