MULTISPECTRAL AND HYPERSPECTRAL THERMAL INFRARED IMAGING FOR MINERAL MAPPING: COMPARISON OF MASTER AND SEBASS

Common rock-forming minerals have abundant spectral absorption features throughout the visible-near infrared (VNIR - 0.4 to 1.0 µm), short-wave infrared (SWIR - 1.0 to 2.5 µm), and thermal infrared (TIR - 8 to 13 µm) wavelength ranges. These features are related to fundamental vibrational frequencies of anion groups such as SiO4, PO4, CO3, and SO4, and are diagnostic, exhibiting measurable variations such as band shifts with cation substitution that permit mineral species identification. Previous work with airborne imagers such as AVIRIS (Airborne Visible-Infrared Imaging Spectrometer), which acquire data in the VNIR/SWIR region, has shown the ability to map minerals remotely. However, in the VNIR/SWIR region alone, common silicate minerals have no spectral absorption features, and there is some overlap between the diagnostic features of mineral groups such as sulfates and clays. In the TIR region sulfate and clay mineral absorptions are clearly separated in wavelength, and can be uniquely identified. In addition, silicates such as quartz and feldspar can be identified and mapped with TIR data.

The MODIS/ASTER airborne simulator (MASTER) was developed jointly by NASA Ames Research Center and the Jet Propulsion Laboratory for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the Terra satellite. MASTER measures radiance in 50 channels between 0.4 and 13 µm with varying ground spatial resolution (5-20 meters) and swath (3.5-14 km), depending on flight altitude. The Spatially Enhanced Broadband Array Spectrograph System (SEBASS) is a new hyperspectral TIR sensor developed and operated by Aerospace Corporation. It is an airborne imaging spectrometer with 128 contiguous bands in both, the 3-5 µm and 8-12 µm atmospheric-window regions, with 2-meter ground spatial resolution and 256-meter swath. SEBASS flight lines over Virginia City and Steamboat Springs, Nevada have been analyzed, and resultant mineral classification maps will be presented and compared to images derived from MASTER data.