FLEX and Sentinel-3C sealed within Vega-C fairing

At Europe's Spaceport in French Guiana, preparations are in final stages for one of the year's most anticipated Earth-observation launches. FLEX and Copernicus Sentinel-3C have been enclosed within the protective fairing of the Vega-C rocket, with liftoff scheduled for 15 September at 03:21 CEST (14 September 22:21 local time).

Encapsulation followed more than six weeks of preparations and involved delicate handling. FLEX was first placed in the lower part of the Vespa secondary payload adapter, which allows multiple satellites on a single launch; Sentinel-3C was then mated to the upper part, so it will be deployed first. The two fairing halves were then sealed, protecting the payload stack from acoustic noise, vibrations, and aerodynamic forces during ascent.

FLEX, or Fluorescence Explorer, is ESA's next Earth Explorer mission. Its Fluorescence Imaging Spectrometer will detect the faint fluorescence emitted by plants during photosynthesis, which varies with plant health and environmental conditions. The mission will produce global maps of vegetation fluorescence at 300 × 300 metre resolution, offering new insights into photosynthetic activity, vegetation stress, and how carbon and water move through ecosystems.

Copernicus Sentinel-3C is the third satellite in the Sentinel-3 series. Its instruments will continue systematic monitoring of Earth's oceans, land, ice, and atmosphere, measuring parameters such as sea-surface temperature, ocean colour, sea level, and sea-ice characteristics.