EFFECT OF A FINITE SPATIAL-COHERENCE OUTER SCALE ON THE COVARIANCES OF ANGLE-OF-ARRIVAL FLUCTUATIONS

The transverse and longitudinal covariances of the angle-of-arrival fluctuations are theoretically calculated, taking into account the effect of a finite outer scale for the spatial coherence of the wavefronts perturbed by the atmospheric turbulence described successively by the Kolmogorov-Tatarski model and the Von Karman model. Estimations of this outer scale can thus be deduced from simultaneous measurements of these covariances and Fried's parameter r0. A numerical simulation supports this statement. The effect of a finite outer scale on differential seeing measurements is estimated for typical experimental conditions. For long baseline interferometry the statistical analysis of angle-of-arrival fluctuations appears to be a very efficient way to obtain the necessary information, as well for site testing as during the observations.