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2611055 
Journal Article 
Continuous outdoor operation of an all-sky polarization imager 
Shaw, JA; Pust, NJ; Staal, B; Johnson, J; Dahlberg, AR 
2010 
Unk 
Proceedings of SPIE
ISSN: 0277-786X
EISSN: 1996-756X 
Proceedings of SPIE 
7672 
WOS:000285627100010 
With the increasing use of polarization as an added dimension in imagery for a variety of scientific, defense, and civilian applications comes a need for better understanding of how the natural environment affects polarization signatures. In the visible and near-infrared spectral range, the most important environmental component is polarized skylight. To provide data to help improve understanding of how atmospheric polarization varies with aerosols, clouds, and surface reflectance, an all-sky polarization imager has been designed, built, calibrated, and operated in a variety of field experiments. This paper describes modifications made to that instrument to enable continuous, unattended outdoor operation. The primary modifications were development of a weather-proof housing and an automated sun occulter incorporating an on-board microcontroller that continually calculates solar position and moves an occulting disk on a thin metal band to prevent direct sunlight from falling on the polarimeter lens. This occulter is designed to not obstruct the principal scattering plane, defined as the plane containing the zenith, the Sun, and the observer. 
Polarization imaging; polarization signatures; clouds; aerosols; atmospheric polarization; skylight