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[1] Interpretation of surface radiation characteristics by overhead hyperspectral imagery often requires a compensation of the measured radiance data for the absorption and emission effects of the intervening atmosphere. We describe a procedure that accounts for these effects by direct use of the hyperspectral radiance data without recourse to ancillary meteorological data or atmospheric modeling. This in-scene atmospheric compensation (ISAC) procedure is applicable to a broad class of problems. The present work concerns terrestrial surface characterization by remote sensing in the 8-13 mm atmospheric window band. A complete ISAC analysis is carried out in two steps. In the first step, unscaled atmospheric compensation spectra (transmittance and upwelling radiance) are extracted from the data. The step is carried out by application of a specially designed, line-fitting procedure to a scatterplot constructed from the hyperspectral data. The compensation spectra are defined in terms of the slope and intercept parameters of the line. In the second step, these unscaled compensation spectra are scaled to quantitative compensation spectra. Here, this step is carried out using the strength of absorption in the 11.7-mm water band. The compensation procedure is demonstrated by application to hyperspectral imagery obtained with the Aerospace Corporation's Spatially Enhanced Broadband Array Spectrograph System (SEBASS) hyperspectral imaging sensor at the Department of Energy's (DOE) Atmospheric Radiation Measurement (ARM) facility. Example applications demonstrate the ability of the method to remove atmospheric spectral structure from the observed data and reveal the spectral structure intrinsic to the underlying surface. This removal is demonstrated both for near-blackbody surfaces composed of grass and for surfaces containing limestone gravel and Red Clay soil.

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We present intermediate-resolution (j/*j B 60) spectra of 21 ultracompact H II regions in the spectral range from 3 to 13 km. The 9.7 km silicate feature is seen in absorption, and the 12.8 km [Ne II] Ðne structure line is seen in emission toward most of the observed nebulae. The strengths of both features vary enormously from nebula to nebula, suggesting large variations in the column densities of both Ne II and silicates toward these objects. Near-IR features attributed to polycyclic aromatic hydrocarbons (PAHs) are detected in six of the sources.Spherically symmetric dust shell models were calculated to obtain the best Ðts to those nebulae for which distances are known, and spectral energy distributions are available in the range of 1 mm to 1 km. The models are used to infer properties of the dust cocoon such as the distribution of density and temperature with radius, shell thickness, outer shell radius, and dust abundances. Our results are consistent with previous models that predict large dust cocoons with central cavities, sharp temperature gradients, and approximately constant density in the outer regions.