Water leaving reflectance that an ocean color mission (such as pace) measures is inherently bidirectional, i.e., IT varies with the position of sun and the viewing direction. This variation, expressed…

This is a $563,293 cooperative agreement awarded by the National Aeronautics and Space Administration (NASA) to the University of Southern Mississippi (USM) to develop a method for improving the Bidirectional Reflectance Distribution Function (BRDF) correction for the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission's Ocean Color Instrument (OCI). The project aims to utilize data from PACE's multi-angle polarimeters, HARP2 and SPEXone, to better understand the natural variability of the volume scattering function's backward shape factor (called the "ch factor") and its impact on remote sensing reflectance. This work is intended to improve the accuracy of BRDF corrections for the OCI, a key component of the PACE mission. The award is not a set-aside contract. USM, a public research university, has a strong track record of providing scientific research, technical services, and support to federal agencies.

Water leaving reflectance that an ocean color mission (such as pace) measures is inherently bidirectional, i.e., IT varies with the position of sun and the viewing direction. This variation, expressed as bidirectional reflectance distribution function (brdf) is ultimately determined by the volume scattering function (VSF), and in particular its backward shape (called CH factor). Previous studes investigating brdf have used the vsfs that evidently underestimate the natural variability of CH factor and could lead to errorshat are greater than the 30% target of retrieving remote sensing reflectance from the pace mission. On the other hand, the two multiangle polarimeters (HARP2 and spexone) that the pace will deploy along with the hyperspectral OCI sensor offer an opportunity to measure CH factor. Taking advantage of this opportunity, we propose to develop a method using multi-angle polarimetry data to derive chactor and improve the brdf correction for pace s OCI remote sensing reflectance (RRS). The proposed work is based on insight and knowledge that we have gained during past decade in studying the natural variability of the volume scattering function and its impact on ocean color. Specifically, we propose to achieve three objectives. (1) improve our understanding of natural variability of the chactor and its impact on bidirectional remote sensing reflectance. Because of the essential role played by the CH factor in determinig the brdf effect, addressing this objective will allows US to develop a mechanistic understanding on the source of variability in brdf. (2) utilize zaneveld s theoretical derivation that explicitly includes VSF in RRS formula to retrieve CH factor from the multi-ngle RRS observation. (3) explore a multi-sensor capability to constrain the brdf correction for the hyperspectral OCI using CH factr retrieved from the multi-angle HARP2 and/or spexone. In additional to improving brdf correction, our method will also retrieve chactor, which as an important inherent optical property, contains critical information on the composition and structure of the particle assemblages in the oceans. Therefore, IT also has potential to derive additional biogeochemical products from the pace mission.