Seminar:Path-Resolved Turbulence Diagnostics: Implications for Adaptive Optics Performance
Nov/13/2009 15:00 Filed in: Seminars
Electro-Optics/Physics Seminar
Friday, November 13, 2009
3:00pm CPC 580
All are invited
Friday, November 13, 2009
3:00pm CPC 580
All are invited
Path-Resolved Turbulence Diagnostics: Implications for Adaptive Optics Performance
Matthew R. Whiteley, Ph.D.
Vice-President / Senior Scientist, MZA Associates Corporation
1360 Technology Ct, Suite 200, Dayton, OH 45430
ABSTRACT
Propagation of visible and infrared wavelengths through the atmosphere is greatly affected by optical turbulence arising from naturally-occurring fluctuations in the index-of-fraction. Dimensional analysis of the scalar wave equation for propagation through atmospheric media reveals that the profile of turbulence strength, Cn2(z) along the path is an important scaling parameter of the resulting field. Conventional turbulence diagnostic methods typically give only path-averaged turbulence strength, and do not provided the required information to capture propagation effects which influence the performance of adaptive optics (AO) systems designed to compensate atmospheric turbulence. We have pioneered a technique and tested instrumentation for measuring the turbulence profile over a propagation path. Using recently-collected turbulence profile data, we illustrate the variability of AO compensation performance which would otherwise be undiagnosed by irradiance scintillometry. We demonstrate the effect by use of a WaveTrain™ wave-optics propagation model of a typical AO system. Numerical simulation of propagation through measured turbulence volumes enables inspection of so-called anisoplanatic effects in AO-compensated imagery. These models also provide estimates of the variability of the probability density function (PDF) of irradiance at a receiver to turbulence profile—both uncompensated and with AO on the transmitter. The PDF of irradiance is a primary metric governing the performance of a laser communication link over an atmospheric path.
Matthew R. Whiteley, Ph.D.
Vice-President / Senior Scientist, MZA Associates Corporation
1360 Technology Ct, Suite 200, Dayton, OH 45430
ABSTRACT
Propagation of visible and infrared wavelengths through the atmosphere is greatly affected by optical turbulence arising from naturally-occurring fluctuations in the index-of-fraction. Dimensional analysis of the scalar wave equation for propagation through atmospheric media reveals that the profile of turbulence strength, Cn2(z) along the path is an important scaling parameter of the resulting field. Conventional turbulence diagnostic methods typically give only path-averaged turbulence strength, and do not provided the required information to capture propagation effects which influence the performance of adaptive optics (AO) systems designed to compensate atmospheric turbulence. We have pioneered a technique and tested instrumentation for measuring the turbulence profile over a propagation path. Using recently-collected turbulence profile data, we illustrate the variability of AO compensation performance which would otherwise be undiagnosed by irradiance scintillometry. We demonstrate the effect by use of a WaveTrain™ wave-optics propagation model of a typical AO system. Numerical simulation of propagation through measured turbulence volumes enables inspection of so-called anisoplanatic effects in AO-compensated imagery. These models also provide estimates of the variability of the probability density function (PDF) of irradiance at a receiver to turbulence profile—both uncompensated and with AO on the transmitter. The PDF of irradiance is a primary metric governing the performance of a laser communication link over an atmospheric path.
