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Proceedings Paper

Airborne Imaging Spectrometer-2: Radiometric Spectral Characteristics And Comparison Of Ways To Compensate For The Atmosphere
Author(s): James E. Conel; Robert O. Green; Gregg Vane; Carol J. Bruegge; Ronald E. Alley; Brian J. Curtiss
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Paper Abstract

A field experiment and its results involving AIS-2 data for Rogers Lake, CA are described. The radiometry and spectral calibration of the instrument are critically examined in light of laboratory and field measurements. Three methods of compensating for the atmosphere in the search for ground reflectance are compared. We find, preliminarily, that the laboratory-determined responsivities are 30 to 50% less than expected for conditions of the flight for both short-and long-wavelength observations. The spectral sampling interval is 20 to 30 nm. The combined system-atmosphere-surface signal-to-noise ratio, as indexed by the mean response divided by the standard deviation for selected areas, lies between 40 and 110, depending upon how scene averages are taken, and is 30% less for flight conditions than for the laboratory. Atmospheric and surface variations may contribute to this difference. It is not possible to isolate instrument performance from the present data. As for methods of data reduction, the so-called scene average or log-residual method fails to recover any feature present in the surface reflectance, probably because of the extreme homogeneity of the scene. The empirical line method returns predicted surface reflectances that are systematically high but within a few percent of actual observed values using either calibrated or uncalibrated data. LOWTRAN-6, acting as an approximate theoretical model of the atmosphere for these exercises, predicts reflectance values 30 to 50% below the measured ones, based on the lower than expected radiances under solar illumination given by the instrument. This emphasizes the importance of accurate radiometric calibration in the study of surface or atmospheric properties.

Paper Details

Date Published: 1 January 1987
PDF: 18 pages
Proc. SPIE 0834, Imaging Spectroscopy II, (1 January 1987); doi: 10.1117/12.942294
Show Author Affiliations
James E. Conel, California Institute of Technology (United States)
Robert O. Green, California Institute of Technology (United States)
Gregg Vane, California Institute of Technology (United States)
Carol J. Bruegge, California Institute of Technology (United States)
Ronald E. Alley, California Institute of Technology (United States)
Brian J. Curtiss, University of Colorado (United States)

Published in SPIE Proceedings Vol. 0834:
Imaging Spectroscopy II
Gregg Vane, Editor(s)

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