HR: 0800h
AN: P21A-0196    [Abstracts]
TI: Pancam Photometric Observations at the Mars Exploration Rover Landing Sites
AU: * Johnson, J R
EM: jrjohnson@usgs.gov
AF: USGS, 2255 N. Gemini, Flagstaff, AZ 86001
AU: Team, A S
EM: jpl.nasa.gov
AF: MER Mission, JPL, Pasadena, ca 00000
AB: The Panoramic Cameras (Pancam) on the Spirit and Opportunity Mars Exploration Rovers have made dedicated multispectral reflectance observations of rocks and soils at different incidence, emission, and phase angles that will be used for photometric modeling of surface materials. Pancam filters normally used for these observations were 432, 601, 753, and 1003 nm. Spirit has made observations at four locations in the Gusev plains pointed along the antisunset and antisunrise directions (photometric equator) at 2-3 times per day. On two occasions these data sets were complemented by additional measurements pointed in orthogonal directions. At the rim of "Bonneville" crater, observations of the crater rim and interior were made at 5 times of day and are supplemented by images acquired as part of panoramas at 4 other times of day. At the Opportunity landing site, three sets of measurements were acquired along the photometric equator within the confines of "Eagle" crater, encompassing both dark soils and outcrop materials. These were supplemented by two near-field, targeted observations of regions containing many hematite-rich spheroidal granules. Additional images were acquired in the plains between "Eagle" and "Endurance" craters at 4 times of day along the photometric equator and at orthogonal directions. Stereo images acquired as part of these sequences are being used to construct surface normal maps from which incidence, emission, and phase angle images are derived for local surface facets (Soderblom et al., this issue). This will improve corrections for diffuse vs. direct sunlight and the derivation of photometric functions and Hapke parameters for rock and soil surfaces. Phase angle coverage at both sites extends from 0 deg to 155 deg. Preliminary analysis of these data reveals increasing reflectance at low phase angles associated with the opposition effect, and increasing reflectance at high phase angles (forward-scattering), particularly for smooth rock facets, fine-grained drift materials, and spherules. These findings are consistent with the results from the Viking and Mars Pathfinder lander cameras. Photometric imaging sequences during the Extended Mission will include the outcrops at the Columbia Hills (Spirit) and the dunes in the interior of "Endurance" crater (Opportunity), acquired during lower atmospheric opacity conditions.
DE: 5460 Physical properties of materials
DE: 5464 Remote sensing
DE: 5470 Surface materials and properties
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting