Pratley, L;
Johnston-Hollitt, M;
McEwen, JD;
(2019)
A Fast and Exact w-stacking and w-projection Hybrid Algorithm for Wide-field Interferometric Imaging.
The Astrophysical Journal
, 874
(2)
10.3847/1538-4357/ab0a05.
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Abstract
The standard wide-field imaging technique, the w-projection, allows correction for wide fields of view for non-coplanar radio interferometric arrays. However, calculating exact corrections for each measurement has not been possible due to the amount of computation required at high resolution and with the large number of visibilities from current interferometers. The required accuracy and computational cost of these corrections is one of the largest unsolved challenges facing next-generation radio interferometers such as the Square Kilometre Array. We show that the same calculation can be performed with a radially symmetric w-projection kernel, where we use one-dimensional adaptive quadrature to calculate the resulting Hankel transform, decreasing the computation required for kernel generation by several orders of magnitude, while preserving the accuracy. We confirm that the radial w-projection kernel is accurate to approximately 1% by imaging the zero-spacing with an added w-term. We demonstrate the potential of our radially symmetric w-projection kernel via sparse image reconstruction, using the software package PURIFY. We develop a distributed w-stacking and w-projection hybrid algorithm. We apply this algorithm to individually correct for non-coplanar effects in 17.5 million visibilities over a 25 by 25 degree FoV Murchison Widefield Array observation for image reconstruction. Such a level of accuracy and scalability is not possible with standard w-projection kernel generation methods. This demonstrates that we can scale to a large number of measurements with large image sizes while still maintaining both speed and accuracy.
| Type: | Article |
|---|---|
| Title: | A Fast and Exact w-stacking and w-projection Hybrid Algorithm for Wide-field Interferometric Imaging |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.3847/1538-4357/ab0a05 |
| Publisher version: | http://dx.doi.org/10.3847/1538-4357/ab0a05 |
| Language: | English |
| Additional information: | This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | image processing, techniques: interferometric, methods: data analysis |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10077392 |
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