Exploration of a Polarized Surface Bidirectional Reflectance Model Using the Ground-Based Multiangle SpectroPolarimetric Imager

Atmosphere

David J. Diner³  Feng Xu³  John V. Martonchik³  Brian E. Rheingans³  Sven Geier³  Veljko M. Jovanovic³  Ab Davis²  Russell A. Chipman¹ 

[1] College of Optical Sciences, University of Arizona, 1630 East University Boulevard, Tucson, AZ 85721, USA; E-Mails:;Center for Space Research, University of Texas, 3925 W. Braker Lane, Suite 200, Austin, TX 78759, USA; E-Mail:;Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA; E-Mails:

关键词: aerosols;    remote sensing;    polarization;    underlying surface reflectance;   

DOI  :  10.3390/atmos3040591

来源: mdpi

【 摘 要 】

Accurate characterization of surface reflection is essential for retrieval of aerosols using downward-looking remote sensors. In this paper, observations from the Ground-based Multiangle SpectroPolarimetric Imager (GroundMSPI) are used to evaluate a surface polarized bidirectional reflectance distribution function (PBRDF) model. GroundMSPI is an eight-band spectropolarimetric camera mounted on a rotating gimbal to acquire pushbroom imagery of outdoor landscapes. The camera uses a very accurate photoelastic-modulator-based polarimetric imaging technique to acquire Stokes vector measurements in three of the instrument’s bands (470, 660, and 865 nm). A description of the instrument is presented, and observations of selected targets within a scene acquired on 6 January 2010 are analyzed. Data collected during the course of the day as the Sun moved across the sky provided a range of illumination geometries that facilitated evaluation of the surface model, which is comprised of a volumetric reflection term represented by the modified Rahman-Pinty-Verstraete function plus a specular reflection term generated by a randomly oriented array of Fresnel-reflecting microfacets. While the model is fairly successful in predicting the polarized reflection from two grass targets in the scene, it does a poorer job for two manmade targets (a parking lot and a truck roof), possibly due to their greater degree of geometric organization. Several empirical adjustments to the model are explored and lead to improved fits to the data. For all targets, the data support the notion of spectral invariance in the angular shape of the unpolarized and polarized surface reflection. As noted by others, this behavior provides valuable constraints on the aerosol retrieval problem, and highlights the importance of multiangle observations.

【 授权许可】

CC BY   
© 2012 by the authors; licensee MDPI, Basel, Switzerland.