Comparison Of Two Techniques For Determining Atmospheric Seeing

Eaton, Frank D.; Peterson, William A.; Hines, John R.; Drexler, J.; Waldie, Arthur Howard; Soules, David B.

doi:10.1117/12.945791

Cited by 18 publications

(7 citation statements)

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“…The statistical variance in the focal point locations, σ 2 XY , is used with the DIMM hardware parameters, including the operational wavelength, λ, the telescope focal length, f , the distance between the apertures, d, and the diameter of the apertures, D, to calculate the atmospheric coherence length for a given atmospheric path. Equation (5) shows this relationship [5,6].…”

Section: (Formentioning

confidence: 99%

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Laser differential image-motion monitor for characterization of turbulence during free-space optical communication tests

2013

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A laser differential image-motion monitor (DIMM) system was designed and constructed as part of a turbulence characterization suite during the DARPA free-space optical experimental network experiment (FOENEX) program. The developed link measurement system measures the atmospheric coherence length (r0), atmospheric scintillation, and power in the bucket for the 1550 nm band. DIMM measurements are made with two separate apertures coupled to a single InGaAs camera. The angle of arrival (AoA) for the wavefront at each aperture can be calculated based on focal spot movements imaged by the camera. By utilizing a single camera for the simultaneous measurement of the focal spots, the correlation of the variance in the AoA allows a straightforward computation of r0 as in traditional DIMM systems. Standard measurements of scintillation and power in the bucket are made with the same apertures by redirecting a percentage of the incoming signals to InGaAs detectors integrated with logarithmic amplifiers for high sensitivity and high dynamic range. By leveraging two, small apertures, the instrument forms a small size and weight configuration for mounting to actively tracking laser communication terminals for characterizing link performance.

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Section: (Formentioning

confidence: 99%

“…These systems are completely passive, using telescopes and starlight to measure the turbulence levels during astronomical observation [4,5]. DIMM techniques also can be employed for the characterization of turbulence horizontally through the atmosphere, assuming a stable remote source at range can be established [6].…”

Section: Introductionmentioning

confidence: 99%

Laser differential image-motion monitor for characterization of turbulence during free-space optical communication tests

2013

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“…First, the DDTV technique is insensitive to contamination due to gimbal motion, a feature of all differential-tilt techniques [14, 15,16]. Secondly, additive noise contributions to the differential-tilt variances are inherently canceled in the DDTV technique.…”

Section: Properties Of Ddtv Measurementsmentioning

confidence: 99%

<title>Differential-tilt technique for saturation-resistant profiling of atmospheric turbulence</title>

Whiteley

Washburn

Wright

2002

Adaptive Optics Systems and Technology II

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A technique for profiling of C over an atmospheric propagation path is proposed, developed and analyzed. The technique employs differential-tilt measurements to arrive at statistics which have unique weighting functions over the propagation path. These weighting functions are computed theoretically and used to derive a reconstructor matrix for C values throughout the path to be applied to an appropriate set of differential-tilt statistics. A candidate optical system is presented, and the performance of the profile reconstructor is analyzed. This study indicates that the relative error in the C estimates is approximately 5%. The relative error in estimating key atmospheric parameters such as the Fried parameter, isoplanatic angle, and the Rytov parameter from the reconstructed profiles is approximately 3%.

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“…Fermat's principle also applies, and light chooses the path of least time. In 3-D space, the index of refraction (n) may vary in any direction, and the actual schlieren angle (8) can be expressed by 181 = 1 Vn • dL (2) where Vn = the refractive index gradient and L = the arc length considered, dependent on the radius of curvature.…”

Section: Schlieren Systeiumentioning

confidence: 99%

Morphology of atmospheric transparent inhomogeneities

Eaton

Peterson

Hines

et al. 1990

Propagation Engineering: Third in a Series

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Observations are presented displaying the evolution of transparent inhomogeneities in the natural atmosphere. All results are for horizontal paths in the first few meters above ground level. Measurements were taken using both a schlieren optical system capable of sensing fine scale gradients of refractive index and an optical system sensing the fine structure of intensity scintillation over various path lengths. Laser sources were utilized for both systems, and a full description of the two optical systems is included. The schlieren system employs two high quality 10-in-diameter mirrors to produce the illuminated working section. Trade-offs between this and other schlieren optical system configurations are discussed. The intensity scintillation measurements were taken with a collimated laser beam projected on a target board. System characteristics including the CCD camera, sampled frame rates, exposure times, and data processing are discussed.The central problem addressed in this study is to identify the conditions when C. Taylor's "frozen turbulence" hypothesis is justified. The optically derived results are compared to results from previous studies using tower, aircraft, and tethered balloon measurements. Analyses presented include histograms, threedimensional displays, contour maps of features, and frame subtraction schemes.Simultaneous measurements of integrated path and point measurements of the refractive index structure parameter (C2) , and wind , are included in the results.

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Comparison Of Two Techniques For Determining Atmospheric Seeing

Cited by 18 publications

References 0 publications

Laser differential image-motion monitor for characterization of turbulence during free-space optical communication tests

Laser differential image-motion monitor for characterization of turbulence during free-space optical communication tests

<title>Differential-tilt technique for saturation-resistant profiling of atmospheric turbulence</title>

Morphology of atmospheric transparent inhomogeneities

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