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Proceedings Paper

Analysis Of UV Limb Data From Low Earth Orbit
Author(s): D. J. Strickland; R. P. Barnes; R. J. Cox; D. E. Anderson Jr.; J. F. Carbary; C. I. Meng
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Paper Abstract

A first-principles optical backgrounds model is applied to the analysis of UV backgrounds data obtained in 1988 from low earth orbit. The basic forms of the data are spectral matrices versus wavelength and tangent altitude (point of closest approach to the Earth's surface along the line of sight). Matrices were obtained in the far UV (FUV), middle UV (MUV), near UV (NUV) and visible spectral regions from about 250 to 0 km tangent altitude. Observing periods include noon, dusk, dawn and midnight. This paper will examine selected MUV and NUV data from the noon period for which the solar zenith angle was about 50°. We have two different interests in the analysis of these data. The first is to better understand optical backgrounds for discrimination purposes. In this case, our interest is on overall approximate behavior of backgrounds and how well our model describes this behavior. This will be the subject of the present paper. Our second interest is a scientific one where the emphasis is on what can be learned from the data about excitation mechanisms and composition. Analysis along these lines will be reported at a later time. From the present analysis, we generally observe agreement to better than 50% between theory and data for Rayleigh scattering of sunlight in both the MUV and NUV regions. This indicates good calibration of the instruments and that the model can be used with confidence to predict this component of the background. Less satisfactory agreement is achieved for the dayglow. While good overall agreement is seen at MUV wavelengths in spectral structure, the data frequently lie above the calculations by factors of two or more. Agreement is worse at NUV wavelengths. We are presently investigating possible sources of the disagreement which include model uncertainties and imperfect off-axis rejection of light by the instruments.

Paper Details

Date Published: 28 December 1989
PDF: 10 pages
Proc. SPIE 1158, Ultraviolet Technology III, (28 December 1989); doi: 10.1117/12.962531
Show Author Affiliations
D. J. Strickland, Computational Physics, Inc. (United States)
R. P. Barnes, Computational Physics, Inc. (United States)
R. J. Cox, Computational Physics, Inc. (United States)
D. E. Anderson Jr., E.O. Hulburt Center for Space Research (United States)
J. F. Carbary, Johns Hopkins University (United States)
C. I. Meng, Johns Hopkins University (United States)

Published in SPIE Proceedings Vol. 1158:
Ultraviolet Technology III
Robert E. Huffman, Editor(s)

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