Geothermal Exploration with Visible through Long Wave Infrared Imaging Spectrometers
G.J. Scherer, D.N. Riley, W.A. Peppin, D.M. Tratt, C. Wright, K.L. Jones
The Aerospace Corporation, US
Keywords: Geothermal, Exploration, Imaging, Spectrometers, Visible, Short wave, Infrared, Long wave
Abstract:Surface minerals of active geothermal systems have been mapped using visible-short wave infrared and mid wave and long wave imaging spectrometers separately. May and June 2008, the Prospectir sensor and SEBASS (Spatially Enhanced Broadband Array Spectrograph System) were located on together on a roll compensated mount viewing through the same camera port in a Twin Otter. These two imaging spectrometers have similar Instantaneous Fields of View (IFOV) and together collect over 600 channels of spectral information from the visible to the long wave infrared. Prospectir collects 357 channels of information in the visible-short wave infrared to map minerals at the surface such as kaolinite, illite, montmorillonite, halloysite, alunite, jarosite, chlorite, calcite, amorphous silica, and travertine. SEBASS collects 256 spectral channels of information, 128 channels in the mid wave and 128 in the long wave infrared. Minerals such as quartz, albite, adularia, orthoclase, kaolinite, Na- and Ca-montmorillonite, opal, chalcedony, alunite, gypsum, jarosite, calcite, and other sulfates can be mapped on the surface using the LWIR. Many of the aforementioned minerals have absorption features that overlap each other in other parts of the electromagnetic spectrum. Mineral mapping for geothermal exploration using combined system allows for the complimentary nature of these combined sensors to effective map the surface and reduce costs by only using one aircraft. Mineral mapping opal and chalcedony at the surface is important for differentiating between ancient sinter deposits and active geothermal systems.