Aperture synthesis

aperture synthesis imagingsynthetic apertureinterferometric imagingaperture-synthesis techniquesynthesised aperturesynthesizedsynthetic-aperturesynthetic-aperture imaging
Aperture synthesis or synthesis imaging is a type of interferometry that mixes signals from a collection of telescopes to produce images having the same angular resolution as an instrument the size of the entire collection.wikipedia
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Astronomical interferometer

astronomical interferometryinterferometerinterferometry
Astronomical interferometers are commonly used for high-resolution optical, infrared, submillimetre and radio astronomy observations.
A mathematical signal processing technique called aperture synthesis is used to combine the separate signals to create high-resolution images.

Radio astronomy

radio astronomerradioradioastronomy
Astronomical interferometers are commonly used for high-resolution optical, infrared, submillimetre and radio astronomy observations.
Radio astronomy is conducted using large radio antennas referred to as radio telescopes, that are either used singularly, or with multiple linked telescopes utilizing the techniques of radio interferometry and aperture synthesis.

Martin Ryle

Sir Martin RyleRyleM. Ryle
Aperture synthesis imaging was first developed at radio wavelengths by Martin Ryle and coworkers from the Radio Astronomy Group at Cambridge University.
Sir Martin Ryle (27 September 1918 – 14 October 1984) was an English radio astronomer who developed revolutionary radio telescope systems (see e.g. aperture synthesis) and used them for accurate location and imaging of weak radio sources.

Very Large Array

VLAEVLAD. S. Heeschen
For example, the Very Large Array has 27 telescopes giving 351 independent baselines at once, and can give high quality images.
Using the rail tracks that follow each of these arms—and that, at one point, intersect with U.S. Route 60 at a level crossing—and a specially designed lifting locomotive ("Hein's Trein"), the antennas can be physically relocated to a number of prepared positions, allowing aperture synthesis interferometry with up to 351 independent baselines: in essence, the array acts as a single antenna with a variable diameter.

Angular resolution

spatial resolutionresolutionresolved
Aperture synthesis or synthesis imaging is a type of interferometry that mixes signals from a collection of telescopes to produce images having the same angular resolution as an instrument the size of the entire collection.
In order to perform aperture synthesis imaging, a large number of telescopes are required laid out in a 2-dimensional arrangement with a dimensional precision better than a fraction (0.25x) of the required image resolution.

Mullard Radio Astronomy Observatory

Mullard Radio Astronomy Observatory (MRAO)MullardMullard Observatory
The radio astronomy group in Cambridge went on to found the Mullard Radio Astronomy Observatory near Cambridge in the 1950s.
The Mullard Radio Astronomy Observatory (MRAO) is located near Cambridge, UK and is home to a number of the largest and most advanced aperture synthesis radio telescopes in the world, including the One-Mile Telescope, 5-km Ryle Telescope, and the Arcminute Microkelvin Imager.

Cavendish Astrophysics Group

Radio Astronomy GroupCambridge Radio Astronomy GroupProfessor of Radio Astronomy
Aperture synthesis imaging was first developed at radio wavelengths by Martin Ryle and coworkers from the Radio Astronomy Group at Cambridge University.
Various aperture masking instruments for optical aperture synthesis

One-Mile Telescope

One-MileOne-Mile Radio Telescope
During the late 1960s and early 1970s, as computers (such as the Titan) became capable of handling the computationally intensive Fourier transform inversions required, they used aperture synthesis to create a 'One-Mile' and later a '5 km' effective aperture using the One-Mile and Ryle telescopes, respectively.
The One-Mile Telescope at the Mullard Radio Astronomy Observatory (MRAO), Cambridge, UK is an array of radio telescopes (2 fixed and 1 moveable, fully steerable 60-ft-diameter parabolic reflectors operating simultaneously at 1407 MHz and 408 MHz) designed to perform aperture synthesis interferometry.

Aperture masking interferometry

aperture maskaperture maskingAperture masks
Some instruments use artificial rotation of the interferometer array instead of Earth rotation, such as in aperture masking interferometry.
Non-redundant masks consist of arrays of small holes where no two pairs of holes have the same separation vector (the same baseline – see aperture synthesis).

Synthetic-aperture radar

synthetic aperture radarSARsynthetic aperture
Aperture synthesis is also used by a type of radar system known as synthetic aperture radar, and even in optical telescopes. Synthetic aperture radar (SAR) and Inverse synthetic aperture radar (ISAR)
Rather than discarding the phase data, information can be extracted from it. If two observations of the same terrain from very similar positions are available, aperture synthesis can be performed to provide the resolution performance which would be given by a radar system with dimensions equal to the separation of the two measurements.

Ryle Telescope

Ryle
During the late 1960s and early 1970s, as computers (such as the Titan) became capable of handling the computationally intensive Fourier transform inversions required, they used aperture synthesis to create a 'One-Mile' and later a '5 km' effective aperture using the One-Mile and Ryle telescopes, respectively.
As the telescope was an east-west instrument, most imaging observations involved 12-hour observations in order to fill the synthesised aperture (calibration observations are routinely interleaved).

Interferometry

interferometerinterferometricoptical interferometry
Aperture synthesis or synthesis imaging is a type of interferometry that mixes signals from a collection of telescopes to produce images having the same angular resolution as an instrument the size of the entire collection. Aperture synthesis is also used by a type of radar system known as synthetic aperture radar, and even in optical telescopes.
An astronomical interferometer achieves high-resolution observations using the technique of aperture synthesis, mixing signals from a cluster of comparatively small telescopes rather than a single very expensive monolithic telescope.

Inverse synthetic-aperture radar

inverse synthetic aperture radarinverse SARISAR
Synthetic aperture radar (SAR) and Inverse synthetic aperture radar (ISAR)
This operation is equivalent to (but the inverse of) the generation of a large synthetic aperture phased array antenna formed by the coherent summation of the receiver outputs for varying target / antenna geometries.

Radar

radar stationradarsradar system
Aperture synthesis is also used by a type of radar system known as synthetic aperture radar, and even in optical telescopes.
Phased-array interferometry or aperture synthesis techniques, using an array of separate dishes that are phased into a single effective aperture, are not typical for radar applications, although they are widely used in radio astronomy.

Beamforming

beam formingbeamformerAntenna beamforming
Beamforming
Aperture synthesis

Light field

light fields4D light field4D light fields
Light field
Synthetic aperture photography: By integrating an appropriate 4D subset of the samples in a light field, one can approximate the view that would be captured by a camera having a finite (i.e., non-pinhole) aperture. Such a view has a finite depth of field. By shearing or warping the light field before performing this integration, one can focus on different fronto-parallel (Isaksen 2000) or oblique (Vaish 2005) planes in the scene. If a digital camera was able to capture the light field (Ng 2005), its photographs would allow being refocused after they are taken.

Synthetic-aperture magnetometry

Synthetic aperture magnetometry
Synthetic aperture magnetometry
* Aperture synthesis

Fourier transform

Fouriercontinuous Fourier transformuncertainty principle
At each separation and orientation, the lobe-pattern of the interferometer produces an output which is one component of the Fourier transform of the spatial distribution of the brightness of the observed object.

Visible-light astronomy

optical astronomyopticalvisible
Astronomical interferometers are commonly used for high-resolution optical, infrared, submillimetre and radio astronomy observations.

Infrared astronomy

infraredinfrared radiationJ, H, and K s bands
Astronomical interferometers are commonly used for high-resolution optical, infrared, submillimetre and radio astronomy observations.

Submillimetre astronomy

submillimetersubmillimeter astronomysubmillimetre
Astronomical interferometers are commonly used for high-resolution optical, infrared, submillimetre and radio astronomy observations.

Amplitude

peak-to-peakintensityvolume
Aperture synthesis is possible only if both the amplitude and the phase of the incoming signal are measured by each telescope.

Phase (waves)

phasephase shiftout of phase
Aperture synthesis is possible only if both the amplitude and the phase of the incoming signal are measured by each telescope.

University of Cambridge

CambridgeCambridge UniversityUniversity
Aperture synthesis imaging was first developed at radio wavelengths by Martin Ryle and coworkers from the Radio Astronomy Group at Cambridge University.

Antony Hewish

Tony HewishHewishHewish, Anthony
Martin Ryle and Tony Hewish jointly received a Nobel Prize for this and other contributions to the development of radio interferometry.