Is adaptive optics the solution to daytime optical downlink communication? This is the question that NASA is hoping to answer at their Optical Ground Stations in California and Hawaii.
  
Adaptive optics on telescopes is not a new idea and has been used in astronomy for decades, providing major observatories with near diffraction-limit conditions over an ever-increasing field of view. Astronomers, however, have a relatively easy job as they operate in nighttime conditions when the atmospheric turbulence is relatively quiet. Optical communication between a satellite and the ground, on the other hand, must be performed at any hour of the day when the turbulence can be significantly stronger.
 
In this paper, the authors describe their approach to this challenge, and detail the hardware and software necessary to meet their 50% coupling efficiency requirement. The correction of the atmospheric turbulence is done by two deformable mirrors and a tip-tilt mirror each responsible for a different range of frequencies and amplitudes of the aberrations. The paper shows the great care needed at the sub system level to maintain the coupling efficiency between the telescope and fiber and demonstrates the feasibility of high-bandwidth laser communications using adaptive optics.

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