Modeling a Temporally Evolving Atmosphere with Zernike Polynomials

This paper develops a new, more accurate temporal model of phase screen generation. The long standing Fourier transform (FT) based method assumes the frozen flow hypothesis holds, where large phase screens are generated and then shifted. The result is a statistically correct screen. Realistically however, the phase changes with time especially when the wind velocity is small or non-existent. The temporal evolution method proposed in this paper is based on expanding a random walk algorithm to the Zernike polynomial method that will include not only the perceived shifting of the Kolmogorov FT method, but also a boiling effect that changes the phase as it shifts. This new method of phase screen generation will be validated through a simulated experiment which measures the correlations of tilt as a function of time and compares that to a predicted tilt correlation function derived using both the frozen flow hypothesis and the new model. This validation experiment will show that the frozen flow model alone fails to accurately predict the temporal correlation of optical tilt. Presented at the 13th annual Advanced Maui Optical and Space Surveillance (AMOS) Technologies Conference on September 11-14, 2012 Maui, Hawaii. The original document contains color images.