Adaptive Optics & Interferometry: Structures & Vocabulary

Adaptive optics and interferometry are two different techniques for improving angular detail. Adaptive optics corrects rapidly changing wavefront distortions from Earth's atmosphere, while interferometry combines signals from separated apertures to synthesize the resolving power of a much larger baseline.

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.

An adaptive-optics loop contains a reference source, wavefront sensor, high-speed computer, and deformable mirror. Natural guide stars or laser guide stars provide wavefront references. An interferometer has at least two collecting elements, delay control, beam combination or electronic correlation, and baseline geometry. The field of correction, sky coverage, coherence time, wavelength, and baseline sampling determine what each system can reconstruct.