<title>Airborne laser experiment (ABLEX): theory and simulations</title>

Abstract

A series of experiments was conducted in January, 1993, in which a pulsed laser beam was propagated from one aircraft to a receiver on board another aircraft. At the receiver, the resulting turbulence induced scintillation patterns across an 80 cm aperture were recorded. The measured irradiance patterns were used to infer the fundamental performance limits imposed by turbulence induced amplitude scintillation on imaging systems and laser transmitters employing adaptive optics to perform phase only compensation. From the data, point and aperture averaged scintillation statistics and amplitude correlation functions were also obtained.We describe the theoretical basis for the measurements. A theoretical analysis, applicable in the weak scintillation regime, is presented. Predictions based on wave optics computer simulations are also presented, and comparisons of the empirical results with the analysis and simulation predictions are shown. The methodology used to analyze the data recorded during the ABLEX tests is also detailed. A description of the experiment and a discussion of the results obtained are presented in a companion paper1.

Flight Measurements of Aero-Optical Distortions from a Flat-Windowed Turret on the Airborne Aero-Optics Laboratory (AAOL)

“…With new more powerful lasers came the ability to deliver more laser energy onto a target and an increased range. However, the shorter wavelength (1-1.5 μm) of new lasers increased the detrimental effects that inhomogeneous refractive mediums [2][3][4] have on the ability of optical systems to focus a laser beam in the farfield.…”

Statistics of time-averaged atmospheric scintillation

“…As an example, suppose we were doing a 3 second illumination of a target from an airplane moving at 240 m/s, and we calculate that for the particular propagation path the expected scintillation Strehl is 0.75. The estimate of the variance of the instantaneous relative intensity from Eq [1] is 0.368. For a 3 second illumination at 240 m/s, the propagation path traverses a distance X of 720 meters.…”

“…The variance of the instantaneous relative intensity for the 63 ABLEX series with at least 90 seconds duration, as a function of the series Strehl. The fit of Eq[1] is shown as the solid line.…”

Statistics of intermediate duration averages of atmospheric scintillation

“…Beginning in January 1993, Phillips Laboratory carried out a series of measurements of scintillation for propagation across long paths through the atmosphere [1][2][3][4] . In the experiment, a laser was emitted from one airplane (Harp), and the intensity profile was measured in a pupil plane scintillometer on a second airplane (the modified NC135 Argus).…”