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Joined 2026-09-21 Message
Incoming links: Aperture synthesis
Aperture synthesis 2026-10-18
Aperture synthesis reconstructs the sky's brightness from complex visibilities measured at different interferometric baselines. Each measurement constrains a Fourier transform component of the brightness, rather than supplying a little photograph. Combining many such components can distinguish sources that each individual antenna leaves unresolved. The remarkable economy is that changing separations and the rotation of Earth can provide many measurements with only a few physical antennas.
Martin Ryle's Cambridge group made aperture synthesis a practical method of astronomical imaging at the Mullard Radio Astronomy Observatory. Cambridge's institutional history connects that work with the One-Mile Telescope and its larger successors.[ref]
Mullard Radio Astronomy Observatory at Lord’s Bridge by Cavendish Laboratory, University of Cambridge. Cavendish Laboratory, Mullard Radio Astronomy Observatory at Lord’s Bridge, sections Foundation and early development and A centre for radio interferometry
In his 1974 lecture Radio Telescopes of Large Resolving Power, Martin Ryle recalled the problem of distinguishing weak extragalactic sources and resolving their structure. He explained sequential wavefront sampling using one simultaneously observed element as a wave phase reference, and the saving obtained by letting Earth rotate the apparent baseline.[ref]
Radio Telescopes of Large Resolving Power by Martin Ryle. Ryle (1974), Radio Telescopes of Large Resolving Power, pp. 187–192, Figures 1 and 4
The 1974 Nobel Prize in Physics distinguished Martin Ryle's observations and inventions, especially aperture synthesis, from Antony Hewish's role in discovering pulsars. The latter is a separate astronomical discovery, with its own observational history.[ref]
The Nobel Prize in Physics 1974 by Nobel Prize Outreach. Nobel Prize in Physics 1974, award explanation and equal prize shares
Nobel Prize in Physics in 1974 2026-10-18
Awarded in equal shares to Martin Ryle and Antony Hewish for pioneering radio astrophysics: Ryle for observations and inventions, especially aperture synthesis, and Hewish for his decisive role in discovering pulsars.[ref]
The Nobel Prize in Physics 1974 by Nobel Prize Outreach. Individual official summary: equal halves; Ryle aperture synthesis and Hewish decisive pulsar-discovery role distinguished.
Radio astronomy 2026-10-18
Radio astronomy studies celestial sources through their radio waves. The long wavelengths make angular resolution expensive: a filled telescope of diameter has a characteristic diffraction scale of order . Aperture synthesis instead combines measurements from separated antennas, using their separations to measure fine structure while their individual collecting areas determine how much radiation they receive. A kilometre-wide arrangement of small antennas does not collect the power intercepted by a filled kilometre-wide dish.
Radio telescope 2026-10-18
A radio telescope is an astronomical instrument that receives radio waves using an antenna and associated receivers. A single dish measures radiation over its directional sensitivity pattern; separated elements can supply complex visibilities for aperture synthesis.