Continuous outdoor operation of an all-sky polarization imager

Shaw, Joseph A.; Pust, Nathan J.; Staal, Benjamin; Johnson, Jennifer E.; Dahlberg, Andrew R.

doi:10.1117/12.851374

Cited by 10 publications

(9 citation statements)

References 16 publications

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“…[2][3][4][5][6][7]32,34 This is a division-of-time imaging polarimeter that uses liquid crystal variable retarders (LCVRs) to tune rapidly through four polarization states rapidly enough to minimize adverse effects of cloud motion. All-sky images are acquired at each of the four polarization states and used in a system-matrix-inversion approach 1 to recover a 4-element Stokes vector at each pixel.…”

Section: All-sky Polarization Imagermentioning

confidence: 99%

“…Because of the difficulty of planning for smoke or any other specific set of atmospheric conditions, we developed an all-sky polarization imager that operates outdoors continually. 34 Included in the multi-year data record from this instrument are numerous measurements of sky polarization with overhead smoke layers that have been transported from distant and regional wildfires. However, in August 2012 we obtained measurements before, during, and after a local wildfire that created a smoke plume that rose into the sky almost directly south of our instrument location on the Montana State University campus (45.662ºN, 111.045ºW) in Bozeman, Montana, USA, and spread out so that within approximately twelve hours it had filled the local valley with thick smoke.…”

Section: Introductionmentioning

confidence: 99%

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Effects of wildfire smoke on atmospheric polarization

Shaw¹,

Pust

Forbes

2014

SPIE Proceedings

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A continuously operating all-sky polarization imager recorded the skylight polarization pattern as conditions transitioned from clear and clean to extremely smoky. This transition included a period when a local wildfire plume filled part of the sky with smoke, creating a highly asymmetric distribution of aerosols. Multiple scattering in the smoke plume strongly reduced the degree of polarization in the smoky region of the sky. Once the smoke plume spread out to cover the entire local sky, the degree of polarization was strongly reduced everywhere. However, this example differed from previously observed smoke events because, even though the usual skylight polarization pattern generally persisted throughout the event, this time the smoke-covered sky exhibited a spatially asymmetric profile along the band of maximum polarization. This pattern of reduced polarization toward the horizon is hypothesized to be a result of an optically thick but physically thin smoke layer. The skylight polarization observations are supplemented with optical depth measurements and aerosol size distribution retrievals from a solar radiometer.

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Section: All-sky Polarization Imagermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of wildfire smoke on atmospheric polarization

Shaw¹,

Pust

Forbes

2014

SPIE Proceedings

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“…Observations generally support this conclusion. [88][89][90][91][92][93][94][95][96] Conditions at twilight with low solar elevations can present some spectral differences.…”

Section: -66mentioning

confidence: 99%

Daytime sky polarization calibration limitations

2016

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The daytime sky has been recently demonstrated as a useful calibration tool for deriving polarization cross-talk properties of large astronomical telescopes. The Daniel K Inouye Solar Telescope (DKIST) and other large telescopes under construction can benefit from precise polarimetric calibration of large mirrors. Several atmospheric phenomena and instrumental errors potentially limit the techniques accuracy. At the 3.67m AEOS telescope on Haleakala, we have performed a large observing campaign with the HiVIS spectropolarimeter to identify limitations and develop algorithms for extracting consistent calibrations. Effective sampling of the telescope optical configurations and filtering of data for several derived parameters provide robustness to the derived Mueller matrix calibrations. Second-order scattering models of the sky show that this method is relatively insensitive to multiple-scattering in the sky provided calibration observations are done in regions of high polarization degree. The technique is also insensitive to assumptions about telescope induced polarization provided the mirror coatings are highly reflective. Zemax-derived polarization models show agreement between the functional dependence of polarization predictions and the corresponding on-sky calibrations.

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“…Aerosols and cloud particles, which are comparable to or larger than the optical wavelength, alter the pure Rayleigh background through scattering processes that do not follow the simple Rayleigh law. Consequently, predicting the polarization pattern observed in the real atmosphere, under conditions other than those leading to pristine Rayleigh scattering, requires careful treatment of the scattering of light by aerosols and cloud particles (Pust and Shaw 2006, 2007, 2009Pust et al , 2009aPust et al , 2009bShaw 2007;Shaw et al 2010). Furthermore, light reflected from the ground mixes with the polarized skylight, generally reducing the net degree of polarization (DoP) observed in the atmosphere .…”

Section: Introductionmentioning

confidence: 99%

Atmospheric Polarization Imaging with Variable Aerosols, Clouds, and Surface Albedo

Shaw¹

2013

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) 7-15-2013 REPORT TYPE Final Technical Report DATES COVERED (From -To)April 2010 -April 2013 TITLE AND SUBTITLEAtmospheric polarization imaging with variable aerosols, 5a. CONTRACT NUMBER Clouds, and surface albedo. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)Montana State University AND ADDRESS(ES) PERFORMING ORGANIZATION REPORT NUMBEROffice of Sponsored Programs 307 Montana Hall Bozeman, MT 59717-0001 SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)Air Force Office of Scientific Research 875 N. Randolph St., Rm. 3112 SPONSOR/MONITOR'S REPORTArlington, VA 22203 NUMBER(S) DISTRIBUTION / AVAILABILITY STATEMENT SUPPLEMENTARY NOTES ABSTRACTAn all-sky polarization spectral imager developed under prior support was deployed along with an atmospheric lidar, a sun-tracking multi-channel solar radiometer, and a variety of groundbased aerosol sensors to study the effect of variable aerosols, clouds, and surface reflectance on skylight polarization in the 450 -780 nm spectral region. The entire sensor suite operated continuously from 2009-2012 except for brief periods of maintenance. This study produced a computer model for predicting clear-sky polarization as a function of aerosol properties and surface reflectance, which was validated with measurements and then used to predict clear-sky polarization spectra for various locations around the world. A surface reflectance with a strong wavelength dependence results in lower skylight degree of polarization at wavelengths with higher surface reflectance. Similarly, changing aerosol types and concentrations lead to spatially and temporally variable skylight polarization. SUBJECT TERMS Executive SummaryEffective prediction and exploitation of polarization signatures in optical remote sensing requires improved understanding of the underlying physical mechanisms and phenomenology. To this end we have developed and deployed an all-sky polarization imager, along with a wide range of atmospheric sensors, to study the influence of aerosols and clouds on skylight polarization in the visible and near-infrared spectral band...

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Continuous outdoor operation of an all-sky polarization imager

Cited by 10 publications

References 16 publications

Effects of wildfire smoke on atmospheric polarization

Effects of wildfire smoke on atmospheric polarization

Daytime sky polarization calibration limitations

Atmospheric Polarization Imaging with Variable Aerosols, Clouds, and Surface Albedo

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