The low-frequency behavior of atmospherically distorted wavefronts is not accurately known at this time. It is expected that the phase delays will be a zero mean random process. A new zero-low-frequency model of spatial PSD of the phase distortions is presented in this paper. This model has a low frequency, called the roll-over frequency, for which the PSD starts to approach zero as the frequency decreases and approaches zero. This roll-over frequency is proportional to the outer-scale of turbulence. To verify the zero-low- frequency model, wavefront slope data was analyzed from the GSM experiment with a nonlinear modelling technique called Robust Orthogonal Search (ROS). One property of ROS is that it can detect frequency components at frequencies lower than the resolution of the discrete Fourier transform. This investigation consistently indicates a lowest frequency in the data for which any lower frequency components have lower power. This results supports the low-frequency model which rolls over and approaches zero for low spatial frequencies.

Date Published: 7 July 2000
PDF: 11 pages
Proc. SPIE 4007, Adaptive Optical Systems Technology, (7 July 2000); doi: 10.1117/12.390365

Published in SPIE Proceedings Vol. 4007:
Adaptive Optical Systems Technology
Peter L. Wizinowich, Editor(s)