When the aperture size of a coherent laser radar is much. larger than the turbulence coherence length, the radar's performance is significantly degraded by turbulence-induced beam distortions. This paper addresses the correction of turbulence effects on such large aperture radars by means of adaptive optics. The radar system model is of a ground-based monostatic radar doing angle-angle imaging of a resolved speckle target located high above the earth's atmosphere. The degradation in performance due to turbulence is quantified. A system for correcting the turbulence distortions is then described and its performance analyzed. The turbulence information for wavefront correction is obtained from the target return. Separation of the speckle and turbulence distortions in the target return is necessary in order to improve the spatial resolution. The system transmits multiple wavelengths to achieve this separation, and gives a spatial resolution within 1.2 times diffraction limited.
Naomi E. Zirkind,
Jeffrey H. Shapiro,
"Adaptive Optics For Large Aperture Coherent Laser Radars", Proc. SPIE 0999, Laser Radar III, (18 February 1989); doi: 10.1117/12.960230; https://doi.org/10.1117/12.960230