Analysis Of UV Limb Data From Low Earth Orbit

D. J. Strickland; R. P. Barnes; R. J. Cox; D. E. Anderson Jr.; J. F. Carbary; C. I. Meng

doi:10.1117/12.962531

28 December 1989 Analysis Of UV Limb Data From Low Earth Orbit

D. J. Strickland, R. P. Barnes, R. J. Cox, D. E. Anderson Jr., J. F. Carbary, C. I. Meng

Proceedings Volume 1158, Ultraviolet Technology III; (1989) https://doi.org/10.1117/12.962531
Event: 33rd Annual Technical Symposium, 1989, San Diego, United States

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.

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D. J. Strickland, R. P. Barnes, R. J. Cox, D. E. Anderson Jr., J. F. Carbary, and C. I. Meng "Analysis Of UV Limb Data From Low Earth Orbit", Proc. SPIE 1158, Ultraviolet Technology III, (28 December 1989); https://doi.org/10.1117/12.962531

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