Mathematics – Logic
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufm.p12b0371k&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #P12B-0371
Mathematics
Logic
5410 Composition, 5464 Remote Sensing, 5470 Surface Materials And Properties, 5494 Instruments And Techniques
Scientific paper
The Melas Chasma trough, in the central complex of Vallis Marineris, provides an ideal site for testing a preliminary approach of deriving surface emissivity from the thermal infrared data produced by the Thermal Emission Imaging System (THEMIS) on the Mars Odyssey spacecraft. Melas Chasma exhibits layered deposits, regional collapse deposits descending from amphitheatres in the walls of the canyon, and various aeolian features. This variety of morphologic features indicates a complex geologic history and a likelihood of compositional heterogeneity in the deposits. The Thermal Emission Spectrometer (TES) on Mars Global Surveyor (MGS) reveals some of the expected spectral variability in this region. However, the 3 km x 6 km pixel resolution of the instrument makes it difficult to associate these variations with geomorphic units visible in the MGS Mars Orbiter Camera (MOC) images or in the THEMIS temperature images. The 100 m pixel size of the THEMIS infrared bands should provide the spatial resolution to associate spectral variability with geomorphology and provide insight into the geologic history of this site. THEMIS data is processed to produce calibrated radiance using the most current calibration model. Camera reflections and other image artifacts are removed or minimized in this process. Geometric corrections of the data are applied to co-register the bands and allow for accurate spectral analysis. Emissivity is produced through a Temperature/Emissivity Separation algorithm. An empirical atmospheric correction using TES derived surface emissivity is used as a proxy for the radiative transfer model atmospheric correction that is not yet available for THEMIS data analysis. Spectral maps are produced from the resulting THEMIS data and the spectral characteristics compared with atmospherically corrected TES and the uncorrected THEMIS data to assess the accuracy of this technique. Evaluation of the nature and composition of these deposits from spectral analysis will follow after a thorough assessment of the accuracy of our emissivity data and atmospheric corrections.
Christensen Per Rex
Knudson Amy T.
Pelkey Shannon M.
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