Aperture synthesis

Aperture synthesis combines signals from multiple antennas to create images with the angular resolution of a telescope as large as the array’s maximum separation.

Radio interferometry: An observing method that combines signals from separated radio telescopes to measure astronomical sources. Aperture synthesis is the imaging form of radio interferometry.
Angular resolution: The smallest angular separation at which an imaging system can distinguish two sources. The array’s longest baselines set its finest attainable angular detail.
Very Long Baseline Interferometry: Radio interferometry that combines telescopes separated by continental or intercontinental distances. Its exceptionally long baselines provide extremely fine angular resolution.
Single-dish radio astronomy: Radio astronomy performed with one dish that collects radiation across a single continuous aperture. A single dish provides continuous sensitivity to broad structures that an interferometer may miss.
Martin Ryle: A British radio astronomer who developed interferometric techniques and received the 1974 Nobel Prize in Physics. Ryle’s work established practical synthesis methods for radio astronomy.
Visibility (radio astronomy): A complex measurement of sky brightness made by correlating signals from a pair of antennas. Each antenna pair in an array samples a visibility used to construct the image.
Spatial frequency: The rate at which a pattern varies across space, often measured in cycles per unit distance. Baselines sample spatial frequencies that correspond to structure at different angular scales.
Event Horizon Telescope: A global radio telescope array that used very long baseline interferometry to image the surroundings of black holes. Its black-hole images depend on aperture synthesis across a planet-scale array.
Optical interferometry: Interferometry at visible or near-infrared wavelengths, where optical path differences must be controlled precisely. It shares the use of separated apertures but faces different coherence and signal-combination constraints.
Cambridge radio astronomy: The research tradition at Cambridge that developed influential radio telescopes and interferometric methods. Cambridge groups built early instruments that demonstrated synthesis imaging.

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