Mathematics – Logic
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufm.p22a0401g&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #P22A-0401
Mathematics
Logic
3934 Optical, Infrared, And Raman Spectroscopy
Scientific paper
The 2003 Mars Exploration Rover science strategy is to identify promising targets using the visible/near-infrared imaging Pancam and the thermal infrared spectrometer Mini-TES. The rover would then traverse to those targets for more detailed examination. Team members will select sites using target morphology and color from Pancam, and interpretations of the mineralogy using Mini-TES. This strategy requires low ambiguity, near real-time interpretations of Mini-TES data. Field spectrometer measurements from a rover perspective differ significantly from both laboratory and airborne measurements. Thus field testing using instrumentation similar to the Mini-TES is required to develop and test methods. We will discuss our field testing research toward that end, with a focus on smooth rock coatings. Researchers desire to detect and characterize smooth rock coatings on Mars, if present. In July 2002, we measured field data of a varnished desert pavement, using equipment that measures very similarly to the Mini-TES. Desert varnish may provide information on the environmental conditions, and interests exobiologists because it may be biologically mediated. Downwelling radiance can affect the spectral character by imparting the spectral character of the downwelling radiance onto the measured target spectrum. The contribution differs from the airborne, laboratory, and field perspectives, and with the surface texture. Downwelling radiance is the thermal energy radiated onto a target by all objects in the hemisphere, including surrounding materials and atmospheric gases and aerosols. Smooth (specular) targets reflect light at the angle of incidence (line-sight), while diffuse targets reflect downwelling radiance integrated from the entire hemisphere. Because even smooth rock coatings are not entirely smooth, they have both diffuse and specular components. Typically the diffuse downwelling component is measured using a high reflectance, rough-surfaced target with a known spectral signature. This is then used to compensate the geologic target for the downwelling component. This assumes that both the downwelling target and the geologic material have the same diffuse and line-site reflected downwelling radiance contributions. This works well for diffuse targets. However, smooth targets have a significant specular component, and the measurement and conversion protocols for these materials are currently poorly understood. The 2003 Mars rover does not carry a diffuse, high-reflectance target for Mini-TES. Thus the diffuse downwelling radiance will have to be estimated from line-sight sky measurements. Development and testing of this procedure and an improved understanding of the required measurement protocols and uncertainties will require field testing. We use Fourier transform infrared interferometers (M100). The M100 raster scans in two dimensions at 25 Hz, and it records the viewing angles with the data. The field of view is 20 or 8 mrad (Mini-TES) vs. 9 mrad (M100); spectral sampling interval 10 vs. 2 wavenumbers; spectral range 5-25 vs. 7.5-13.5 microns; and mast height 1.4 vs. 2-3 meters for the Mini-TES vs. M100, respectively.
Greenhagen Benjamin T.
Herr Kenneth C.
Kirkland Laurel Ellyn
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