The first on-sky demonstration of intensity-based angular phase estimation

Area of Science:

• Optical engineering
• Astronomy
• Atmospheric physics

Background:

• High data-rate ground-to-satellite optical links face signal attenuation due to atmospheric turbulence.
• Existing adaptive optics (AO) systems using downlink correction are limited by phase anisoplanatism, especially with the point-ahead angle (PAA).

Purpose of the Study:

• To demonstrate the first on-sky application of a model-based AO estimator for uplink turbulence pre-compensation.
• To validate a method optimizing pre-compensation phase at the PAA using downlink data and turbulence priors.

Main Methods:

• Utilized close visual binary stars (30 μrad separation) for on-sky testing.
• Employed an open-loop Shack-Hartmann wavefront sensor.
• Applied a model-based estimator incorporating downlink phase, intensity, and turbulence statistical priors.

Main Results:

• Achieved up to a 28% reduction in anisoplanatic tip errors compared to traditional phase-only estimation.
• Demonstrated agreement between experimental results and theoretical predictions.
• Validated the effectiveness of the model-based approach in mitigating uplink turbulence effects.

Conclusions:

• The model-based AO estimator is effective for on-sky pre-compensation of uplink turbulence.
• This method offers a significant improvement over existing techniques for ground-to-satellite optical links.
• Successful demonstration paves the way for more robust and reliable free-space optical communication systems.