Detector perturbation of ocean radiance measurements

The effect of a detector on the ocean radiance field being measured has been investigated - first, in a simple model which accounts for perturbations in the radiance field introduced by the detector shadow and by light reflecting from the detector, and second, by a complete three-dimensional solution of the radiation transfer equation which calculates the perturbations by using a computer model of a 4π radiance detection system (RADS2) with sky and ocean parameter choices to match California coastal water. Results show that the presence of the detector has little influence on downwelling measurements nor do changes in detector reflectance. There is a substantial change due to the detector of upwelling radiance values. This may cause measured values to be reduced by as much as 30% below the unperturbed radiance for systems of the size of RADS (0.5 m) for light coming from the region of the detector shadow. The upwelling irradiance for this case is reduced 10%. Results are given for sensors 0.S m high and having diameters from 0.125 m to 2 m.