Updates to the Polarization Version of SPIRITS," J. A. Conant, F. J. Iannarilli, D. C. Robertson, 12th SPIRITS User Group Meeting, Hanscom AFB, MA, 12-16 May, 2008.

SPIRITS has been extended previously to compute polarized target body radiances, in an unofficial version. In this paper we report on updates on the model. This version of polarized SPIRITS is based on the latest non-polarized version (AC2r2). The model uses a polarized reflectance-emittance sub-model which combines the Sandford-Robertson approach (used in the standard SPIRITS) with the Fresnel/Mueller equations, resulting in a model which includes the most important polarization properties, is easy to use, and gives total radiances identical to those of version AC2r2. The polarized SPIRITS also utilizes recent additions, including improved handling of wide glint lobe reflections, and plume reflections off of the body. We also present a polarized version of MODTRAN™4 which we propose to integrate into SPIRITS, as it will impact the SPIRITS computations in the Visible and SWIR regions.