13 September 2007 All-sky polarization imaging
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We describe measurements of atmospheric polarization made with an all-sky imaging spectro-polarimeter in five 10- nm-wide bands from 450 to 700 nm. The instrument uses two liquid crystal variable retarders and a fixed linear polarizer to measure the Stokes vector in each pixel of a 1 Mpixel image that covers the entire sky dome. Degree of polarization and angle of polarization images are shown for clear, partly cloudy, and smoke-filled conditions. Aerosols and clouds generally reduce the degree of polarization observed throughout the image, even in clear portions of partly cloudy skies. Comparisons of measurements and calculations show that the single-scattering algorithm in the early polarized Modtran (Mod-P) radiative transfer code provide adequate prediction of sky polarization at red and near-infrared wavelengths for low aerosol optical depths (~≤ 0.2), but significantly under-predict the degree of polarization for short wavelengths, especially with higher optical depths and in the vicinity of clouds.
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Nathan J. Pust, Nathan J. Pust, Joseph A. Shaw, Joseph A. Shaw, } "All-sky polarization imaging", Proc. SPIE 6682, Polarization Science and Remote Sensing III, 668204 (13 September 2007); doi: 10.1117/12.736330; https://doi.org/10.1117/12.736330

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