Sentinel-3C

Sentinel-3C carries FLEX as a co-passenger, pairing the constellation's ocean-and-land surface monitoring data with a new measurement capability: solar-induced chlorophyll fluorescence, the faint light emitted by vegetation during photosynthesis. The two spacecraft are designed to work in tandem: FLEX orbits approximately 100 km ahead of Sentinel-3C, allowing both to overfly the same ground strip within seconds of each other and combine their data into a picture of global plant health and photosynthetic activity.