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K. E. Herkenhoff, J. R. Johnson (U. S. Geological Survey), M. Lemmon (Texas A&M), P. H. Smith (Univ. of Arizona)
The range of colors and albedos of materials at the Pathfinder landing site is similar to that observed in Viking Orbiter and HST images of Mars, but precise comparisons are hampered by the effects of atmospheric scattering in these data sets and differences in the effective wavelengths of the images. Such comparisons will allow the spectral units observed at the Pathfinder landing site to be placed into a global geologic context, and the composition, physical properties, and origins of Martian surface units to be inferred. We report our progress toward achieving these objectives by calibrating, modeling, and analyzing IMP multispectral observations of various surface materials and comparing them to the color and albedo units observed by the Viking Orbiter cameras, the WF/PC2 on HST, and the MOC wide-angle cameras on MGS.
New digital terrain models (DTMs) have been derived from IMP stereo data, and new multispectral image cubes of IMP panoramas have been assembled using improved ISIS radiometric calibration, geometric registration and mosaicking software. The latest version of the IMP calibration software yields significantly different relative reflectances in some cases, but in general changes are small. We have also calibrated and assembled a mosaic of Insurance Pan images, which were losslessly compressed and taken under different illumination/viewing conditions than Super Pan; these data will be useful in better constraining the photometric and atmospheric models that are critically important to this investigation. Software tools were developed that evaluate and apply the University of Arizona atmospheric radiative transfer model. Scene reflectivity (as seen from orbit, in an arbitrary geometry) was simulated, including both direct and diffuse components to allow shadow brightness to be predicted. Surface normals from the new DTM were used to simulate sky brightness as a function of direction and predict the scene appearance for a given surface reflectivity.
The author(s) of this abstract have provided an email address for comments about the abstract: kherkenhoff@usgs.gov