'FLEX' was a regular topic of conversation during the POLWET survey in the summer. This was one of the final candidates for ESA's 8th earth explorer mission and there were high hopes that it would be selected. FLEX is designed to measure fluorescence worldwide and therefore would obviously be of key interest to OPTIMISE. Fluorescence can give an idea of how well a plant is photosynthesising, so if you can successfully measure fluorescence then you can locate crops under stress almost immediately, rather than waiting for colour changes using the traditional NDVI route when in some cases the damage is already done.
FLEX's successful selection as the 8th earth explorer mission was announced some time ago but a recent post on ESA's LinkedIn page has some good info and images, such as the one I have used here.
Launch in 2022.