Showing papers by "Brett W. Denevi published in 2007"

Near-infrared optical constants of pyroxene as a function of iron and calcium content

Abstract: [1] We derive the imaginary coefficient of the complex index of refraction (k) from reflectance spectra of 30 pyroxenes using the method of Lucey (1998). We apply the modified Gaussian model of Sunshine et al. (1990) to these k spectra to obtain two continuum parameters and nine Gaussian parameters that describe the 1, 2, and 1.2 μm crystal field absorptions. This method takes advantage of the redundancy in the data and minimizes the number of free parameters, resulting in a compact expression of optical constants that is less susceptible to noise in the data and contamination from terrestrial weathering. Multiple regression results indicate that the continuum and Gaussian parameters are well predicted by pyroxene FeO and CaO contents; thus a complete k spectrum for pyroxene can be derived from arbitrary FeO and CaO concentrations. The uncertainty is highest for the 1.2 μm M1 crystal field absorption in both orthopyroxene and clinopyroxene. These k spectra can be used with radiative transfer theory to produce model reflectance spectra of particulate silicate surfaces at different viewing geometries, particle sizes, levels of space weathering, and mixtures with other minerals.

High-performance Sagnac interferometer using uncooled detectors for infrared hyperspectral applications

Abstract: Results of field testing of a LWIR hyperspectral imager based on a Sagnac interferometer and uncooled microbolometer array are presented. Signal to noise ratios of nearly 1000 are found for 30 bands across the LWIR (8-14 microns) at useful data collection rates (7000 spectra/second). Spectra are compared to those collected simultaneously with a cryogenic LWIR hyperspectral system (U. Hawaii AHI).