Isoplanatic degradation of tilt correction and short-term imaging systems

An MTF is derived that includes isoplanatic effects of tilt correction or short-term imaging systems. By means of the MTF, degradation in Strehl ratio or resolution due to tilt decorrelation on offset paths is predicted for long horizontal paths through constant turbulence, and for space-to-earth paths through a path-dependent structure constant. It is shown that to limit the loss in performance to 10%, the range times the offset angle, divided by diameter, must be less than 0.1-0.5, depending on the ratio of aperture diameter to Yura's phase coherence length.