Optical EngineeringConformal phased array aero-optical modeling and compensation
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The effect of subsonic turbulent boundary layer aero-optical disturbances on a conformal phased array for laser beam projection operating on a high-speed aircraft is considered. We employ a basic model for subsonic boundary layer disturbances developed by Cress et al. which is governed by the displacement thickness δ ∗ to bound the magnitude of the problem, to determine the basic phenomenology affecting phased array performance, and to quantify requirements for compensation of these disturbances in the array subapertures. We used δ ∗ =15 mm as a baseline value in quantifying phased array effects on a 7-aperture hexagonal array with 10 cm subapertures. Boundary layer piston and tilt disturbances dominate array effects, but higher-order disturbances are similar in magnitude to the differential piston over the array and 2× greater in magnitude than an upper bound on free-stream turbulence. Adaptive optics compensation of turbulent boundary layer disturbances in such a phased array requires error rejection bandwidths <1 kHz for high-fidelity array performance.