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8 October 2015 Ultimate turbulence experiment: simultaneous measurements of Cn2 near the ground using six devices and eight methods
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We have performed a series of experiments in order to simultaneously validate several devices and methods for measurement of the path-averaged refractive index structure constant ( 𝐶𝑛 2). The experiments were carried out along a horizontal urban path near the ground. Measuring turbulence in this layer is particularly important because of the prospect of using adaptive optics for free-space optical communications in an urban environment. On one hand, several commercial sensors were used: SLS20, a laser scintillometer from Scintec AG, BLS900, a largeaperture scintillometer, also from Scintec, and a 3D sonic anemometer from Thies GmbH. On the other hand, we measured turbulence strength with new approaches and devices developed in-house. Firstly, an LED array combined with a high-speed camera allowed for measurement of 𝐶𝑛 2 from raw- and differential image motion, and secondly a two-part system comprising a laser source, a Shack-Hartmann sensor and a PSF camera recoded turbulent modulation transfer functions, Zernike variances and angle-of-arrival structure functions, yielding three independent estimates of 𝐶𝑛 2. We compare the measured values yielded simultaneously by commercial and in-house developed devices and show very good agreement between 𝐶𝑛 2 values for all the methods. Limitations of each experimental method are also discussed.
© (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Lydia Yatcheva, Rui Barros, Max Segel, Detlev Sprung, Erik Sucher, Christian Eisele, and Szymon Gladysz "Ultimate turbulence experiment: simultaneous measurements of Cn2 near the ground using six devices and eight methods", Proc. SPIE 9641, Optics in Atmospheric Propagation and Adaptive Systems XVIII, 964105 (8 October 2015);

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