Adaptive Optics & Interferometry: Observation, Measurement & Evidence

An adaptive-optics system uses a reference source, wavefront sensor, high-speed control computer, and deformable mirror. An interferometer combines light or radio signals from multiple telescopes with accurately known delays and baselines.

Corrected images show narrower point-spread functions and higher Strehl ratios than uncorrected images. Interferometers such as the Very Large Array and ALMA reconstruct images from many baseline measurements and achieve resolution far beyond one dish of comparable diameter.

Adaptive optics measures wavefront errors many times per second and reshapes a mirror to apply the opposite distortion. Interferometry preserves phase information so signals from separated antennas or telescopes interfere coherently, encoding source structure at angular scales set by wavelength divided by baseline.

AO performance is measured with Strehl ratio, corrected point-spread functions, residual wavefront error, and guide-star geometry. Interferometers measure calibrated visibilities and closure phases using reference stars or sources. Earth rotation changes projected baselines and fills the Fourier plane. Reliable imaging requires careful calibration because atmospheric piston, instrument drift, and incomplete baseline coverage can create structure that is not actually present in the source.