Direct wide-field radio imaging in real-time at high time resolution using antenna electric fields

James Kent, Adam P. Beardsley, Landman Bester, Steve F. Gull, Bojan Nikolic, Jayce Dowell, Nithyanandan Thyagarajan, Greg B. Taylor, Judd Bowman

Research output: Contribution to journalArticle

Abstract

The recent demonstration of a real-time direct imaging radio interferometry correlator represents a new capability in radio astronomy. However, wide-field imaging with this method is challenging since wide-field effects and array non-coplanarity degrade image quality if not compensated for. Here, we present an alternative direct imaging correlation strategy using a direct Fourier transform (DFT), modelled as a linear operator facilitating a matrix multiplication between the DFT matrix and a vector of the electric fields from each antenna. This offers perfect correction for wide field and non-coplanarity effects. When implemented with data from the Long Wavelength Array (LWA), it offers comparable computational performance to previously demonstrated direct imaging techniques, despite having a theoretically higher floating point cost. It also has additional benefits, such as imaging sparse arrays and control over which sky coordinates are imaged, allowing variable pixel placement across an image. It is in practice a highly flexible and efficient method of direct radio imaging when implemented on suitable arrays. A functioning electric field direct imaging architecture using the DFT is presented, alongside an exploration of techniques for wide-field imaging similar to those in visibility-based imaging, and an explanation of why they do not fit well to imaging directly with the digitized electric field data. The DFT imaging method is demonstrated on real data from the LWA telescope, alongside a detailed performance analysis, as well as an exploration of its applicability to other arrays.

Original languageEnglish (US)
Pages (from-to)254-263
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Volume491
Issue number1
DOIs
StatePublished - Jan 1 2020

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Keywords

  • Instrumentation: interferometers
  • Techniques: image processing
  • Techniques: interferometric

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Kent, J., Beardsley, A. P., Bester, L., Gull, S. F., Nikolic, B., Dowell, J., Thyagarajan, N., Taylor, G. B., & Bowman, J. (2020). Direct wide-field radio imaging in real-time at high time resolution using antenna electric fields. Monthly Notices of the Royal Astronomical Society, 491(1), 254-263. https://doi.org/10.1093/mnras/stz3028