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We have recently demonstrated in peer-reviewed publications how polarimetry can deliver measurements of the ocean surface refractive index. The method exploited observations from the NASA GISS Research Scanning Polarimeter (RSP) within the sunglint region, where the degree of linear polarization is determined by the fundamental Fresnel laws of specular reflection, regardless of the windspeed. At short-wave infrared wavelength, essentially unaffected by atmospheric scattering, the degree of polarization is therefore a direct function of the surface refractive index.

We intend to extend the method to PACE observations from the HARP-2 and SPEXone sensors. Although such instruments lack polarized channels in the SWIR similar to those of RSP, the method can be applied to the NIR wavelengths provided corrections to the aerosol contributions are applied. We will therefore (ii) perform advanced inversions of RSP polarimetric data using the NIR wavelengths in place of the SWIR; (ii) simulate PACE observations of the ocean surface under a range of conditions, and analyze their information content via a rigorous assessment of the uncertainties; and (iii) create a novel "ocean surface refractive index"-type of product for every HARP2 pixel within the sunglint region. We anticipate the results to be useful for investigations of processes involving the ocean surface, and for the detection of oil spills (specifically mentioned in the solicitation) and other contaminants. The study will also help recovering the significant portion of pixels otherwise discarded from PACE imagery as “sunglint- contaminated”, by turning them into a useful resource for new products associated with the retrieval of the ocean surface refractive index.