TURBULENCE CHARACTERIZATION BY STUDYING LASER BEAM WANDERING IN A DIFFERENTIAL TRACKING MOTION SETUP

D. G. PÉREZ, L. ZUNINO, D. GULICH, G. FUNES, AND M. GARAVAGLIA

Berlín, Alemania

Conferencia; XII Optics in Atmospheric Propagation and Adaptive Systems; 2009

SPIE (Society of Photographic Instrumentation Engineers) is the international society for optics and photonics.

The Differential Image Motion Monitor (DIMM) is a standard and widely used instrument for astronomical seeing measurements. The seeing values are estimated from the variance of the differential image motion over two equal small pupils some distance apart. The twin pupils are usually cut in a mask on the entrance pupil of the telescope. As a differential method, it has the advantage of being immune to tracking errors, eliminating erratic motion of the telescope. The Differential Laser Tracking Motion (DLTM) is introduced here inspired by the same idea. Two identical laser beams are propagated through a path of air in turbulent motion, at the end of it their wander is registered by two position sensitive detectors-at a count of 800 samples per second. Time series generated from the difference of the pair of centroid laser beam coordinates is then analyzed using the multifractal detrended fluctuation analysis. Measurements were performed at the laboratory with synthetic turbulence: changing the relative separation of the beams for different turbulent regimes. The dependence, with respect to these parameters, and the robustness of our estimators is compared with the non-differential method. This method is an improvement with respect to previous approaches that study the beam wandering.