Total And Polarized Radiance From The Ocean Surface From Hyperspectral Polarimetric Imaging

Results are presented for measurements of the total and polarized radiances from the ocean surface by a state-of-the-art snapshot hyperspectral imager, which simultaneously acquires spectra with 4nm spectral resolution in the wavelength range of 450-950nm within a 40 degrees field-of-view. The imager does not require any along track movement and allows the continuous collection of hyperspectral imagery from stationary structures or slow moving platforms such as ships or helicopters. In addition, a computer controlled filter wheel is installed in front of the imager allowing for division-of-time Stokes vector images from the ocean surface. Experiments are aimed at the application of the multi-angular polarimetric measurements for the retrieval of water parameters in addition to the ones retrieved from traditional unpolarized methods. Several sets of measurements used in the analysis were acquired from ocean platform in the NYC area, Duck, NC and from shipborne observations in the Gulf of Mexico and along the Florida coast. Measurements made by the imager are compared with simulations using a vector radiative transfer code showing good agreement. Analysis of pixel-to-pixel variability of the total and polarized above water radiance for the viewing angles of 20 degrees-60 degrees in different wind conditions enable the estimation of uncertainties in measurements of these radiances in un-polarized and polarized modes for the whole spectral range, thus setting requirements for the quality of polarized measurements. Impacts of aerosols on spectral variations of both the radiance and the polarized terms of the Stokes vector are studied.