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Proceedings Paper

Profiling of atmospheric turbulence along a path using two beacons and a Hartmann turbulence sensor
Author(s): Santasri R. Bose-Pillai; Jack E. McCrae Jr.; Matthew D. Wilson; Andrew L. Back; Christopher A. Rice; Steven T. Fiorino
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Paper Abstract

The Hartmann Turbulence Sensor (HTS) is an optical system capable of estimating several atmospheric turbulence parameters, such as Greenwood frequency, Fried’s coherence diameter and inner scale of turbulence. It primarily comprises of a 40 cm Meade telescope, a 32 x 32 Shack- Hartmann lenslet array, and a high-speed camera. The HTS estimates the turbulence parameters by measuring the local tilts of the aberrated wavefront coming from a laser source and incident at the pupil plane of the telescope. At the Air Force Institute of Technology (AFIT), a technique has been developed to measure the distribution of turbulence along an experimental path using the HTS and two laser sources of the same wavelength. By measuring the variances of the difference in wavefront tilts due to the two sources sensed by a pair of Hartmann subapertures with varying separations, turbulence information along the path can be extracted. The method relies on deriving a set of weighting functions, each weighting function dipping to zero at a range where the two sensing paths from the beacons to the subapertures intersect, thus canceling out the effect of turbulence at this location on the differential tilt signal. The analytical expression for the path weighting functions has been derived here. The technique has been applied to experimental data collected over a 500 m grassy path and the profiling results have been compared to a co-located scintillometer. This work will eventually aid in obtaining a better understanding of turbulence in the lower atmosphere and how it varies with height.

Paper Details

Date Published: 18 September 2018
PDF: 12 pages
Proc. SPIE 10772, Unconventional and Indirect Imaging, Image Reconstruction, and Wavefront Sensing 2018, 107720C (18 September 2018); doi: 10.1117/12.2321719
Show Author Affiliations
Santasri R. Bose-Pillai, Air Force Institute of Technology (United States)
Applied Research Solutions (United States)
Jack E. McCrae Jr., Air Force Institute of Technology (United States)
Matthew D. Wilson, Air Force Institute of Technology (United States)
Applied Research Solutions (United States)
Wright State Univ. (United States)
Andrew L. Back, Air Force Institute of Technology (United States)
Applied Research Solutions (United States)
Miami Univ. (United States)
Christopher A. Rice, Air Force Institute of Technology (United States)
Steven T. Fiorino, Air Force Institute of Technology (United States)


Published in SPIE Proceedings Vol. 10772:
Unconventional and Indirect Imaging, Image Reconstruction, and Wavefront Sensing 2018
Jean J. Dolne; Philip J. Bones, Editor(s)

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