Estimation of turbulent degradation and required spatial resolution of adaptive systems

Vladimir P. Lukin; Boris V. Fortes

doi:10.1117/12.332418

7 December 1998 Estimation of turbulent degradation and required spatial resolution of adaptive systems

Vladimir P. Lukin, Boris V. Fortes

Proceedings Volume 3494, Atmospheric Propagation, Adaptive Systems, and Lidar Techniques for Remote Sensing II; (1998) https://doi.org/10.1117/12.332418
Event: Remote Sensing, 1998, Barcelona, Spain

Abstract

A laser beam propagating in the atmosphere are influenced simultaneously by thermal blooming and turbulence that result in aberrations of a focal spot. Turbulent aberrations prevail at large speed of scanning, from this point of view they are more important. On the contrary, effectiveness of correction for turbulent aberrations decreases when the object velocity increases. Turbulent aberrations do not depend on sped of angular scanning but in the case of a moving object the requirements to the adaptive system bandwidth are higher than that for a motionless target. The stated above is also true for the low atmosphere paths when a source is placed on the earth and an object altitude is a few kilometers. In this case the influence of thermal blooming is less comparing with turbulence because the coefficient of atmospheric absorption decreases more abruptly than intensity of turbulent aberrations. Additional factor of thermal blooming decreasing is angular scanning. Even when the turbulent and nonlinear aberrations are of the same order, correction for thermal blooming is easier because scales of thermal aberrations are greater and frequencies lower. The only exception is a homogeneous path in the absence of scanning. In this case the strong thermal lens which appears near the beam focus may induce instability and decrease of control efficiency. For a moving object this effect can be disregarded.

Citation Download Citation

Vladimir P. Lukin and Boris V. Fortes "Estimation of turbulent degradation and required spatial resolution of adaptive systems", Proc. SPIE 3494, Atmospheric Propagation, Adaptive Systems, and Lidar Techniques for Remote Sensing II, (7 December 1998); https://doi.org/10.1117/12.332418

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