title: Analysis of multiwavelength observations of optical scintillation.
abstract: Results are presented from an experimental study of the effects of wavelength, range, and thermal turbulence intensity on the laser scintillation magnitude, represented by the log-intensity standard deviation, sigma. During the first phase of the study, intensity fluctuations at 0.6328 microm were measured over a nearground horizontal path for six ranges out to 7.6 km. Similar measurements were made during the second phase at four ranges out to 2.5 km for three wavelengths: 0.4880 microm, 0.6328 microm, and 1.064 microm. A 5-mm diam receiver aperture was used in all cases. During both phases, concurrent measurements of the refractive-index-structure function C(n) were obtained. It was observed that the measured scintillation (sigma(m)) at 0.6328 microm reached a mean maximum of 1.05 when the theoretical Tatarski value (sigma(t)) was 2.5 and then decreased at larger sigma(t) to a value about 0.5, where the scintillation showed evidence of leveling off. The mean maximum scintillation at 0.4880 microm is 1.09, and at 1.064 microm it is 0.82; the ratios of the maxima are well approximated by the minus seven-twelfths power of the wavelength. At large sigma(t) values, the scintillation depends only slightly on wavelength.
authors.forename: W F
authors.initials: WF
authors.lastname: Dabberdt
authors.forename: W B
authors.initials: WB
authors.lastname: Johnson