DECOMPOSITION OF AVIRIS SPECTRA - EXTRACTION OF SURFACE-REFLECTANCE, ATMOSPHERIC, AND INSTRUMENTAL COMPONENTS

We present techniques that use only information contained within a raw , high-spectral-resolution, hyperspectral Airborne Visible/Infrared Im aging Spectrometer (AVIRIS) scene to estimate and remove additive comp onents (atmospheric scattering and instrument dark current), These tec hniques allow normalization of multiplicative components (instrument g ain, topography, atmospheric transmission) and enhancement, extraction , and identification of relative-reflectance information related to su rface composition and mineralogy, Our derivation of additive component s from raw AVIRIS data is based on an adaptation of Crippen's ''regres sion intersection method (RIM).'' As does RIM, we use pairs of surface units that are spectrally homogeneous, spatially extensive, and locat ed in rugged terrain, However, our technique utilizes the long-wavelen gth spectral data of AVIRIS to derive and remove atmospheric scatterin g components for each unit. AVIRIS data from the Kelso Dunes and Grani te Mountain areas of southern California served as spectrally contrast ing, topographically modulated surfaces for illustration of this techn ique. For a given site and wavelength pair, subtraction of the wavelen gth-dependent additive component from individual bands will remove top ographic shading in both sites in band-to-band ratio images, Normaliza tion of all spectra in the scene to the average scene spectrum results in cancellation of multiplicative components and produces a relative reflectance scene. Absorption features due to mineral absorptions that depart from the average spectrum can be identified in the relative-re flectance AVIRIS product, The validity of these techniques is demonstr ated by comparisons between relative-reflectance AVIRIS spectra derive d from application of this technique and those derived by using the st andard calibration techniques of JPL. Calibrated spectra were extracte d from an AVIRIS scene of the Upheaval Dome area of Canyonlands Nation al Park, UT, Results show that surface-reflectance information can be extracted and interpreted in terms of surface mineralogy after applica tion of these techniques to AVIRIS data.