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Proceedings Paper

Ground-To-Satellite Laser Beam Irradiance Due To Diffraction, Turbulence, And Adaptive Optics
Author(s): George W. Sutton
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Paper Abstract

This paper reports the results of calculations on the wavelength sensitivity of the irradiance of a laser beam due to the combined effects of diffraction and atmospheric turbulence, for propagation through the earth's atmosphere to an orbiting satellite. In particular, the issue of the optimum wavelength selection which minimizes the effective beam spread is determined for the following effects: wavelength, from 0.5 μm to 10 μm; long time turbulence; short time turbulence (perfect tilt correction); non-isoplanaticity, since the satellite is in motion; perfect higher order corrections, various zenith angles; and large aperture diameters. The new results differ from the results of previous studies in several aspects. First, the transmitter is located on a mountain as opposed to sea level to reduce the effects of atmospheric turbulence and extinction. Numerical evaluations are presented of the mean-square tilt angular pointing error for non-isoplanatic effects for both zenith and off-zenith angles. The resulting mean-square pointing error scales very closely to the -2.11 power of aperture diameter, and -1.75 power of the cosine of the zenith angle for a lead angle of 52 microradians, based on the profile of Barletti, et al. The results, for 3 to 4 meter diameter apertures, indicate that the minimum beam spread is always in the infrared, for all zenith angles. In the infrared, the beam spread angle can be decreased by 50% with tilt correction, with the spread at 10.6 μm wavelength smaller than that for 3.8 μm, although the beam spread angle is relatively insensitive to the infrared wavelength. Still smaller beam spreads can be achieved at the short wavelength end of the infrared spectrum only by using higher order adaptive optics to compensate for atmospheric turbulence; while the longer wavelengths can benefit from still larger diameters without the necessity for the use of higher order turbulence corrections.

Paper Details

Date Published: 19 December 1979
PDF: 7 pages
Proc. SPIE 0195, Atmospheric Effects on Radiative Transfer, (19 December 1979); doi: 10.1117/12.957939
Show Author Affiliations
George W. Sutton, Avco Everett Research Laboratory, Inc. (United States)

Published in SPIE Proceedings Vol. 0195:
Atmospheric Effects on Radiative Transfer
Claus B. Ludwig, Editor(s)

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