Very Long Baseline Interferometry

Very Long Baseline Interferometry (VLBI) combines radio signals recorded at widely separated telescopes to synthesize a telescope with extremely high angular resolution.

Radio interferometry: A method that combines radio waves received at separate antennas to measure their interference and improve angular resolution. VLBI is a form of radio interferometry that extends baselines across large distances.
Event Horizon Telescope: A global array of radio observatories that uses VLBI to image emission near black holes. Its observations combined stations worldwide to resolve the shadows of M87* and Sagittarius A*.
Radio astronomy: The study of celestial objects and phenomena through their radio emissions. VLBI is a radio-astronomy technique that combines observations across separated sites.
Connected-element interferometer: An interferometer whose antennas are linked by cables or dedicated communications links for coordinated signal processing. Unlike VLBI, connected arrays can combine signals in real time over their local network.
Interferometer: An instrument that combines waves from multiple paths to measure their interference. VLBI uses interferometric principles to extract spatial information from radio signals.
Radio astrometry: The measurement of celestial positions and motions using radio observations. VLBI provides highly precise positions for compact radio sources.
Angular resolution: The ability of an instrument to distinguish two nearby points in angle on the sky. VLBI's exceptionally long baselines produce its defining fine angular resolution.
Aperture synthesis: A method that reconstructs an image from measurements made with different interferometer baselines. VLBI relies on aperture synthesis to turn sparse baseline data into radio images.
Radio telescope: An instrument that detects radio waves from astronomical sources. Each VLBI station records radio waves with its own telescope.
International Celestial Reference Frame: A celestial coordinate system realized by the measured positions of distant extragalactic radio sources. VLBI observations establish and maintain its most accurate realizations.

Linked from 39 pages