Two Air Force Special Weapons Center NC-135 jet aircraft, one carrying a laser transmitter and the other a receiver, were used in an airborne laser-beam scintillation experiment in order to measure high-altitude values of the index-of-refraction structure parameter, Cn2. Measurements were made at a wavelength of 0.6328 μm. Transmitter–receiver spacings of 0.5, 1.0, 1.5, 2.0, and 3.0 km were used. Altitude values ranged from 1.5 to 10.5 km in approximately 1.5-km steps. Computed log-irradiance scintillation parameters included probability distribution function, cumulative probability, variance, and temporal power-spectral density. Irradiance fluctuations were typically log-normal and temporal power spectra agreed reasonably well with theory. Measured values of Cn2 were consistently larger than expected at high altitudes. Some contribution to the measured values of Cn2 may have come from boundary-layer turbulence near the transmitting aircraft. However, this contribution was small. On the average, the upper atmosphere is more turbulent than current models predicted it to be.
© 1973 Optical Society of AmericaFull Article | PDF Article
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