Multispectral photometric properties of the Martian surface at the Mars Exploration Rover landing sites

Mars Exploration Rover (MER) Panoramic Camera (Pancam) observations include multispectral data sets designed to support photometric analysis of Martian surface materials. This dissertation describes the numerical inversion of Pancam radiance on sensor data to determine the optimum spectral bidirectional reflectance model parameter configuration for the surfaces at the MER landing sites. The optimized reflectance models provide constraints on surface properties and allow the scattering characteristics of the materials at each landing site to be directly compared.; Radiance on sensor forward models are calculated using a customized implementation of the multiple scattering Discrete Ordinate Radiative Transfer (DISORT) package. The DISORT implementation includes a plane-parallel model of the Martian atmosphere developed from landed and orbital atmospheric observations and is capable of modeling all radiative processes that contribute to the observed radiance. The reflectance of the lower boundary in the DISORT implementation is specified by the Hapke bidirectional reflectance function in conjunction with a two parameter Henyey-Greenstein scattering phase function. The integration of the Hapke bidirectional reflectance with DISORT allows synthetic Pancam radiance on sensor images to be generated given an atmospheric and surface bidirectional reflectance model configuration and the observation geometry.; For each Pancam image in the photometric data set, a multidimensional radiance lookup table is generated that spans the requisite geometric and model parameter space. Optimization of the bidirectional reflectance model parameter set is conducted with a Levenberg-Marquardt nonlinear least squares algorithm where the iterative radiance forward models are calculated by multilinear interpolation within the appropriate model radiance hypercube.; Modeling results show that the single scattering albedo monotonically increases with wavelength (435, 600, 750, 1005 nm) at both landing sites, with the MER-A surface significantly brighter than the MER-B surface at all but the shortest visible wavelengths. With the exception of the MER-A 435 nm data both surface reflectance models have backscattering phase functions at all sampled wavelengths. The MER-A scattering phase functions exhibit larger backscattering lobes while the MER-B phase functions show greater asymmetry. The spectral variability of the model MER-B surface roughness is an indication of the coupled textural and compositional heterogeneity of the surface at the MER-B landing site.