The bidirectionality of the marine reflectance, which derives from the anisotropy of the underwater light field, is an important parameter in ocean optics. For ocean color remote sensing, especially for multi sights sensor like geostationary satellite, this parameter is need to correctly interpret data.
A predictive model exists  for case 1 waters, whereas there is presently no model for optically-complex case 2 waters. In both cases, a very few number of in-situ measurement has been done due to the lake of dedicated instrument.
The bidirectionality of the marine reflectance can be expressed as the ratio between the
upwelling irradiance (Eu) and the upwelling radiance (Lu) in a given direction :
Q depends on :
- The sun position (θs) - The observation direction (θv, Δφ)
- Water optical properties (IOPs, in particular - The wavelength (λ)
the Volume Scattering Function)
The radiance camera developed in this project is an underwater multi-spectral instrument characterized by a large-angle optic, a high-sensitivity CMOS and a compact design. It has been developed by the CIMEL companies under the overall supervision of the LOV.
Some characteristic of this instrument are given bellow:
- radiance measurement on a full hemisphere (184° field of view).
- measurements capability of upwelling or downwelling light field.
- multispectral measurements (406, 438, 494, 510, 560 and 628 nm)
- extremely compact
reduce self-shading (Ø96 *
- high sensitive CMOS sensor, 12 bit digitization, HD format (1920 x 1080)
- telecentric, non achromatic, patented fish-eye optics
- auxiliary sensors : compass, depth sensor, tilt sensor, Int. Temp. & humidity
- deployment capability down to 100m depth
View from the rear deck of the R/V “Atalante”
Optics design (patented)
deployed at surface to measure upwelling radiance
Q factor measurement @ 560 nm
From LOV : David Antoine (PI), Edouard Leymarie, André Morel, Bernard Gentili, Francis Louis
From CIMEL : Jean Pierre Buis, Nicolas Buis, Stéphane Victori, Sylvain Meunier, Marius Canini
From CNES : Bertrand Fougnie, Patrice Henry