Image processing tools to improve THEMIS-based compositional analysis accessibility

Abstract:

The Thermal Emission Imaging System (THEMIS) on Mars Odyssey includes a 10-band multispectral infrared imager with ~100 m/pixel spatial resolution from ~6.8 to 14.9 µm. THEMIS data provide the planetary science community the ability to study the composition of much of the martian surface. However, THEMIS data have been underutilized for surface spectral analysis due to the lack of a fully automated atmospheric correction tool or surface emissivity products. Here we present the progress of our efforts to develop tools to perform atmospheric correction for THEMIS daytime radiance images. Atmospheric correction of THEMIS images involves correcting for atmospheric emission and atmospheric transmission/absorption from dust and water ice aerosols. This work will provide THEMIS data that have had the atmospheric emission component removed through the PDS (Planetary Data System). However, the correction for atmospheric transmission/absorption requires some user intervention and therefore is only semi-automatic. The semi-automated tool for correcting for atmospheric absorption and transmission is based on TES (Thermal Emission Spectrometer) emissivity. For the correction of atmospheric emission/absorption, a command-line tool is being developed where the user will input a THEMIS image ID and select a continuous area with pre-processed TES pixels that have been selected for quality overlain on the THEMIS image using the Davinci software package (a tool developed and maintained by Arizona State University). Once the region has been collected, this tool will automatically derive the average surface emissivity of the selected TES pixels and the map coordinates. The tool then applies atmospheric correction for a region of the THEMIS image which does not violate quality control assumptions (e.g. large topography changes). The output images are projected and atmospheric corrected with formats following the standards of PDS, which are ready for various studies of surface properties of Mars.