Deriving an estimate for the Fried parameter in mobile optical transmission scenarios.

Measuring the Fried parameter r(0) (atmospheric optical coherence length) in optical link scenarios is crucial to estimate a receiver's telescope performance or to dimension atmospheric mitigation techniques, such as in adaptive optics. The task of measuring r(0) is aggravated in mobile scenarios, when the receiver itself is prone to mechanical vibrations (e.g., when mounted on a moving platform) or when the receiver telescope has to track a fast-moving signal source, such as, in our case, a laser transmitter on board a satellite or aircraft. We have derived a method for estimating r(0) that avoids the influence of angle-of-arrival errors by only using short-term tilt-removed focal intensity speckle patterns.