HR: 0800h
AN: P21A-0199    [Abstracts]
TI: Radiative Transfer Photometric Analysis of Surface Materials at the Mars Exploration Rover Landing Sites
AU: * Seelos, F P
EM: seelos@wunder.wustl.edu
AF: Washington University, Department of Earth and Planetary Sciences, Campus Box 1169, One Brookings Drive, St. Louis, MO 63130 United States
AU: Arvidson, R E
AF: Washington University, Department of Earth and Planetary Sciences, Campus Box 1169, One Brookings Drive, St. Louis, MO 63130 United States
AU: Guinness, E A
AF: Washington University, Department of Earth and Planetary Sciences, Campus Box 1169, One Brookings Drive, St. Louis, MO 63130 United States
AU: Wolff, M J
AF: Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301 United States
AB: The Mars Exploration Rover (MER) Panoramic Camera (Pancam) observation strategy included the acquisition of multispectral data sets specifically designed to support the photometric analysis of Martian surface materials (J. R. Johnson, this conference). We report on the numerical inversion of observed Pancam radiance-on-sensor data to determine the best-fit surface bidirectional reflectance parameters as defined by Hapke theory. The model bidirectional reflectance parameters for the Martian surface provide constraints on physical and material properties and allow for the direct comparison of Pancam and orbital data sets. The parameter optimization procedure consists of a spatial multigridding strategy driving a Levenberg-Marquardt nonlinear least squares optimization engine. The forward radiance models and partial derivatives (via finite-difference approximation) are calculated using an implementation of the DIScrete Ordinate Radiative Transfer (DISORT) algorithm with the four-parameter Hapke bidirectional reflectance function and the two-parameter Henyey-Greenstein phase function defining the lower boundary. The DISORT implementation includes a plane-parallel model of the Martian atmosphere derived from a combination of Thermal Emission Spectrometer (TES), Pancam, and Mini-TES atmospheric data acquired near in time to the surface observations. This model accounts for bidirectional illumination from the attenuated solar beam and hemispherical-directional skylight illumination. The initial investigation was limited to treating the materials surrounding the rover as a single surface type, consistent with the spatial resolution of orbital observations. For more detailed analyses the observation geometry can be calculated from the correlation of Pancam stereo pairs (J. M. Soderblom et al., this conference). With improved geometric control, the radiance inversion can be applied to constituent surface material classes such as ripple and dune forms in addition to the soils on the Meridiani plain. Under the assumption of a Henyey-Greenstein phase function, initial results for the Opportunity site suggest a single scattering albedo on the order of 0.25 and a Henyey-Greenstein forward fraction approaching unity at an effective wavelength of 753 nm. As an extension of the photometric modeling, the radiance inversion also provides a means of calculating surface reflectance independent of the radiometric calibration target. This method for determining observed reflectance will provide an additional constraint on the dust deposition model for the calibration target.
DE: 5464 Remote sensing
DE: 5470 Surface materials and properties
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting