Measuring the spatial detail between samples and satellite pixels

Regulatory and research programmes commonly combine discrete sampling, flow-through systems, and satellite observations. These methods work at different spatial and temporal scales. A satellite views the water through roughly 100 km of atmosphere, which can account for up to 90% of the signal recorded at the sensor, while shipboard sampling leaves wider intervals between individual observations.

A LIF lidar supplies its own light and can therefore operate during the day or at night. From a vessel or small aircraft, the LIFL-11 records a 48-band spectrum in about fifteen seconds at a station or measures four selected bands at up to 10 Hz underway. At 10 kn, that rate places about 20 observations within one 10 × 10 m Sentinel-2 pixel. When the survey is timed to an overpass, active LIF and passive Rrs measurements can be paired with the corresponding satellite observation.

OQOMETHI, funded by France 2030 through ADEME's Innov'Eau call, is developing a network of up to 1,000 micro-observatories for French lakes, rivers, and coastal lagoons. SubseaLIF applies related fluorescence methods within the water column for the detection of organic contamination before it reaches the surface. LIFeLiDAR's responsibility in both programmes is instrument development. The measurements address established needs under the Water Framework Directive, the Marine Strategy Framework Directive, and Copernicus cal/val work.