A new and potentially serious optical-system beam degradation is discussed. The degradation, which we define here as centroid anisoplanatism, deals with the errors and corresponding on-axis intensity reduction that are obtained when centroid or wave-front gradient tracking systems are employed to determine the overall atmospheric-turbulence-induced tilt in short-term imaging and/or laser transmitting systems. The error between overall tilt and centroid measurements becomes more important both at shorter wavelengths and for large-diameter optics. It is also exacerbated by point-ahead limitations and scintillation. Specifically, it is shown that a Strehl ratio of less than 3 × 10−2 results for D/r0 ≳ 100, where D is the optics aperture diameter and r0 is the turbulence-induced lateral coherence length.
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Yura et al. (1985) studied this question.