The Fluorescence Explorer (FLEX) Mission: From Spectral Measurements to High-Level Science Products

The Fluorescence Explorer (FLEX) mission was selected in 2015, by the European Space Agency (ESA), as an Earth Explorer mission, with a launch planned for 2024. The key scientific objective of the mission is the quantitative global mapping of actual photosynthetic activity of terrestrial ecosystems, as a function of variable vegetation health status and environmental stress conditions. The measurements will have a spatial resolution of 300 m, adequate to resolve land surface processes associated to vegetation dynamics at a global scale. To be able to accomplish such objective, the FLEX mission carries the FLORIS spectrometer, specially optimized to map vegetation fluorescence with a spectral sampling of 0.1 nm, and is designed to fly in tandem with Copernicus Sentinel-3. Together with FLORIS, the OLCI and SLSTR instruments on Sentinel-3 provide all the necessary information to retrieve the emitted fluorescence, and to allow proper interpretation of the spatial and temporal dynamics of vegetation photosynthesis from such global measurements.