An improved spectral calibration requirement for AVIRIS

AN IMPROVED SPECTRAL CALIBRATION REQUIREMENT FOR AVIRISRobert O. GreenJet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109andUniversity of California, Santa Barbara, CA 931061. INTRODUCTIONThe Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) measures spectra from 400 to 2500nm through 224 contiguous spectral channels. These spectra are used to identify and determine theabundances of constituents of the Earth's surface and atmosphere through the analysis of spectral molecularabsorptions and scattering properties of materials. Spectral calibration of the AVIRIS is required to pursuethese determinations, which are based on these fundamental spectral characteristics.The spectral calibration of AVIRIS consists of a description of the spectral response function foreach of the 224 spectral channels. The spectral response function of AVIRIS channels was measured in thelaboratory and shown to be Gaussian in shape (Chrien et al. 1990). Figure 1 shows a subset of nine AVIRISspectral channels with channel centers at 10 nm intervals and channel shapes of Gaussian form with 10 nmfull width and half maximum (FWHM). For AVIRIS the spectral calibration is described by the spectralcenter and FWHM of a Gaussian function for each channel. Uncertainty in the determination of the spectralcenter and FWHM for each channel are also reported.This paper presents results from an investigation of the sensitivity of AVIRIS-measured upwellingradiance to errors in spectral calibration. Based on this sensitivity analysis in conjunction with earlier work(Green et al., 1990), an improved spectral calibration requirement for AVIRIS is proposed.2. AVIRIS MEASURED RADIANCEAVIRIS measures the upwelling spectral radiance from the sun that was reflected by the surface aswell as absorbed and scattered by the intervening atmosphere. To investigate the effect of spectralcalibration on measurement of the upwelling radiance, a high resolution spectrum of the radiance arriving at