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Proceedings Paper

Implications of measured differences in the spectroradiometric sensitivity of SBUV/2 instruments in air and vacuum on long-term measurements of stratospheric ozone and solar irradiance variations
Author(s): William K. Fowler; Kevin W. Kelly; Donald F. Heath
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Paper Abstract

In recent years, the consistency of ultraviolet solar spectral irradiance measurements has improved to the extent that broad band averages of solar irradiances agree to within a few percent over ranges of a few hundred nanometers. Over spectral ranges from tens to tenths of nanometers significantly larger disagreements in spectral irradiances are observed. Some well known factors which contribute to measurement uncertainties over smaller wavelength intervals are wavelength calibration errors, uncertainties in radiometric standards especially in the transition region from one standard to another, and differences and uncertainties in slit scattering function between instruments. Extensive pre-launch radiometric calibration of SBUV-2 ozone monitoring instruments in air and vacuum have indicated new sources of radiometric calibration uncertainties. These are effects of Woods anomalies in grating efficiency and wavelength dependent changes (sometimes with significant structure) in the reflectance of MgF2 overcoated aluminum surfaces which seems to be associated with the absorption and desorption of water vapor by the MgF2 thin film. These effects combine to produce wavelength dependent radiometric calibration differences between air and vacuum conditions of as much as 10 percent or more. These results indicate that one should not assume that an accurate radiometric calibration in air is valid in space for the wavelength region of 200 - 400 nm.

Paper Details

Date Published: 8 November 1996
PDF: 15 pages
Proc. SPIE 2815, Optical Radiation Measurements III, (8 November 1996); doi: 10.1117/12.257143
Show Author Affiliations
William K. Fowler, Ball Aerospace & Technologies Corp. (United States)
Kevin W. Kelly, Ball Aerospace & Technologies Corp. (United States)
Donald F. Heath, Research Support Instruments, Inc. (United States)

Published in SPIE Proceedings Vol. 2815:
Optical Radiation Measurements III
James M. Palmer, Editor(s)

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