Mapping natural and human influenced acid sulfate weathering near Reno, NV using the SEBASS hyperspectral instrument

The region near Reno, Nevada, provides a unique opportunity to compare acid rock weathering from a natural source with exposures that occur primarily from anthropogenic activities. The initial phase of the study focuses on mapping the presence and abundance of sulfate minerals using a new hyperspectral thermal infrared airborne sensor SEBASS (Spatially Enhanced Broadband Array Spectrograph System), developed and flown by Aerospace Corporation. In a group shoot in Fall of 1999 the Arthur Brant Exploration group at LTNR obtained 3 flights over Virginia City, Geiger Grade and Steamboat Springs. The instrument measures 128 spectral channels from 7.8 to 13.5 μm with a ground spatial resolution of 2 m and a signal to noise of 2000:1. The ground \´swath of each flight is 128 pixels or approximately 256 m. For initial comparisons the data were corrected to radiance using the "In the Scene Atmospheric Correction" QSAQ routine provided by Aerospace Corporation. This approach corrects for absorption by atmospheric gasses and the surface reflection of sky radiance to reduce the measured radiance to that emitted by the surface. This radiance value is then, divided by a Planck curve to remove the wavelength dependence of radiance on temperature. The resulting values are then surface emissivity which can be directly \´compared with library and laboratory mineral spectra