From 26 to 28 May the team worked the coastal waters off Boulogne-sur-Mer and out into the eastern English Channel aboard the Sépia II, in collaboration with the Laboratoire d’Océanologie et de Géosciences (LOG), whose marine station at Wimereux operates the vessel and sits on the same coast. The full instrument suite went out together, the LIFL-11 and two mFL-12 lidars putting laser light into the water and the mHR-2 radiometer reading the surface passively beside them.
The water was clear across the three days, and what mattered was the change along the transect rather than any single condition. Coastal water gives way to open-Channel water off Boulogne, and the suite read that shift from close inshore out into the Channel.
The instruments read the same water by active and passive means at once, the lidars measuring the fluorescence of what is dissolved and suspended in the water and the radiometer estimating the reflectance an ocean-colour satellite sees from orbit, with conventional sampling taken alongside as the reference the instruments are checked against.
Our thanks to the Laboratoire d’Océanologie et de Géosciences and to Cédric Jamet, and to the crew of the Sépia II who took us out and back over the three days.