Direct Imaging Digital Lens for Transient Radio Source Survey

Daishido, T.; Asuma, K.; Nishibori, K.; Nakajima, Jun; Yano, Motoko; Otobe, Eiichiro; Watanabe, Naoki; Tsuchiya, Akira; Iwase, Seiichiro

doi:10.1017/s0252921100013105

Cited by 2 publications

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“…Direct Fourier transform imagers (Daishido et al 1991;Foster et al 2014) provide another alternative to both of the above approaches. Direct imaging forgoes the calculation of antenna cross products.…”

Section: Introductionmentioning

confidence: 99%

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A real-time, all-sky, high time resolution, direct imager for the long wavelength array

Kent

Dowell

Beardsley

et al. 2019

Monthly Notices of the Royal Astronomical Society

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The future of radio astronomy will require instruments with large collecting areas for higher sensitivity, wide fields of view for faster survey speeds, and efficient computing and data rates relative to current capabilities. We describe the first successful deployment of the E-field Parallel Imaging Correlator (EPIC) on the LWA station in Sevilleta, New Mexico, USA (LWA-SV). EPIC is a solution to the computational problem of large interferometers. By gridding and spatially Fourier transforming channelised electric fields from the antennas in real-time, EPIC removes the explicit cross multiplication of all pairs of antenna voltages to synthesize an aperture, reducing the computational scaling from O(n 2 a ) to O(n g log 2 n g ), where n a is the number of antennas and n g is the number of grid points. Not only does this save computational costs for dense arrays but it produces very high time resolution images in real time. The GPU-based implementation uses existing LWA-SV hardware and the high performance streaming framework, Bifrost. We examine the practical details of the EPIC deployment and verify the imaging performance by detecting a meteor impact on the atmosphere using continuous all-sky imaging at 50 ms time resolution.

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Section: Introductionmentioning

confidence: 99%

“…Previous direct imagers such as Daishido et al (1991);Foster et al (2014) have relied on antennas being on a regular grid, which limits their application from a scientific standpoint. For example, their uniform layouts yield point spread functions that contain periodic grating responses that are not ideal for imaging applications.…”

Section: Introductionmentioning

confidence: 99%

A real-time, all-sky, high time resolution, direct imager for the long wavelength array

Kent

Dowell

Beardsley

et al. 2019

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…This avoids the challenges of full-field imaging with an FX correlator, but with an associated compromise of limited sky coverage. Direct Fourier transform imagers (Daishido et al 1991;Foster et al 2014) provide another alternative to both of the above approaches. Direct imaging forgoes the calculation of antenna cross products.…”

Section: Introductionmentioning

confidence: 99%

“…Previous direct imagers such as Daishido et al (1991); Foster et al (2014), have relied on antennas being on a regular grid, which limits their application from a scientific standpoint.…”

mentioning

confidence: 99%

Interferometric Methods

2005

Shock Waves

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Future radio telescopes promise great advances in resolution and sensitivity. These include the Square Kilometer Array, a two array instrument, in South Africa and Australia. Similarly, the next generation Very Large Array (ngVLA) is being designed for construction in North America. These arrays all promise exceptional advances in sensitivity, angular resolution, and survey speed. The SKA and ngVLA are both specified to have sensitivities at the level of µJy's. The SKA-Low instrument will consist of a huge number of dipoles antennas in Australia which is pushing the bounds of current FX correlator technology with O(n 2 ) scaling, where n is the number of antennas. The design proposals for these instruments include a dense core of antennas, necessitating advances in imaging methods for these very dense cores versus more traditionally sparse instruments.Another ambitious experiment is the Hydrogen Epoch of Reionisation Array (HERA) in South Africa which hopes to make the first direct detection of the Epoch of Reionisation through the red-shifted H signal which is a factor of 10 5 smaller than the thermal-like noise.In this thesis, these problems are tackled by re-examining the underlying principles of interferometry. The first working example of a direct imaging correlator is presented which allows images to be formed directly from the voltages off each antenna in a dense array, without an expensive cross-correlation operation as is typically required. A detailed discussion is given of how standard steps in interferometric imaging differ in this new scheme, including calibration. Additionally the first wide field direct imaging correlator is presented, which allows the problems of non-coplanarity to be dealt with for both sparse and dense arrays in a very efficient manner on modern GPU compute hardware. These are, to the best of the authors knowledge, the only working implementations of a direct imaging correlator for generic arrays with no restrictions on the geometry of the array or homogeneity of constituent receiver elements. These new approaches have been published in the scientific literature as discussed in the Declaration.Moving on from this, the closure phase bispectrum is presented as a way of uncovering the cosmological Epoch of Reionisation signal from the H line. This is using the HERA telescope, which consists of a dense core of parabolic antennas in a highly redundant layout. A data iii reduction and processing pipeline for the HERA telescope is constructed and presented, for use with the bispectrum. Initial results towards a cosmologial limit are reported.The HERA telescope relies on redundancy in its antenna elements for its calibration and measurement strategy. The bispectrum with its unique mathematical propeties, in combination with forward modelling, is shown to be a potent tool for probing departures from the assumed reudundancy. It is shown, through this method, that HERA suffers significant directiondependent non-redundancies in the dataset used for our analysis, which are extremely difficul...

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Direct Imaging Digital Lens for Transient Radio Source Survey

Abstract: FFT based 2D Dygital Lens is discussed comparing with Fourier synthesis. The sensitivity of constructing Large Array will be 50mJy. Precise manipuration of the radiation field is possible in it.

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A real-time, all-sky, high time resolution, direct imager for the long wavelength array

A real-time, all-sky, high time resolution, direct imager for the long wavelength array

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