From 7 to 9 October the whole instrument suite went to sea together for the first time. In the Venice lagoon we operated the LIFL-11 multi-wavelength LIF lidar, the 1.75 kg mFL-12, and the passive mHR-2 radiometer side by side, as part of the European Space Agency’s PHY2FLEX campaign, with vessel support from Italy’s Consiglio Nazionale delle Ricerche (CNR).
Laboratory performance is not sea performance, and the campaign was there to find the gap. Spray, vessel motion, and shifting light all work against an optical instrument, and all three ran through three days of it and returned clean data.
The pairing is what makes the suite worth carrying. The mHR-2 measures above-water remote-sensing reflectance (Rrs), the same quantity an ocean-colour satellite estimates from orbit, and on 8 October it recorded example Rrs spectra in the lagoon. In the same water at the same time, the active LIF sensors measured what was actually in it. That combination is a satellite match-up: the orbital estimate, and the ground truth for it, taken in one place at one moment. Producing them densely, rather than a handful per cruise, is the point of running the two together.