FLEX mission: NPL responsible for SI-traceable validation of vegetation measurements from orbit
On 16 September 2026 the UK’s National Physical Laboratory reported that it validates the surface reflectance and at-surface irradiance products of the European Space Agency’s FLEX mission. The satellite was launched on 15 September on a Vega-C rocket together with Sentinel-3C.
- FLEX is ESA’s first mission dedicated to measuring vegetation fluorescence; the FLORIS imaging spectrometer measures sunlight reflected from vegetation and the extremely faint fluorescence emitted by plants during photosynthesis, in the visible and near-infrared range.
- Working within the FLEX DISC cluster, NPL validates the surface reflectance and at-surface irradiance products and advises on uncertainty estimation for the products themselves and for their validation.
- SI-traceable validation rests on the HYPERNETS and INSIF reference site networks; NPL recently installed a new HYPERNETS site in a grass field at Wytham Woods in Oxford.
- Throughout the mission NPL will produce the operational validation reports; FLEX flies in tandem with the Sentinel-3 satellites, combining FLORIS measurements with data on reflectance, land surface temperature and the atmosphere.
Source: National Physical Laboratory — Monitoring Earth’s photosynthesis from space