Direction Dependent Corrections in Polarimetric Radio Imaging III: A-to-Z Solver -- Modeling the full Jones antenna aperture illumination pattern

Abstract

In this third paper of a series describing direction dependent corrections for polarimetric radio imaging, we present the the A-to-Z solver methodology to model the full Jones antenna aperture illumination pattern (AIP) with Zernike polynomials. In order to achieve thermal noise limited imaging with modern radio interferometers, it is necessary to correct for the instrumental effects of the antenna primary beam (PB) as a function of time, frequency, and polarization. The wideband AW projection algorithm enables those corrections provided an accurate model of the AIP is available. We present the A-to-Z solver as a more versatile algorithm for the modeling of the AIP. It employs the orthonormal circular Zernike polynomial basis to model the measured full Jones AIP. These full Jones models are then used to reconstruct the full Mueller AIP repsonse of an antenna, in principle accounting for all the off-axis leakage effects of the primary beam. The A-to-Z solver is general enough to accomodate any interferometer for which holographic measurements exist, we have successfully modelled the AIP of VLA, MeerKAT and ALMA as a demonstration of its versatility. We show that our models capture the PB morphology to high accuracy within the first 1-2 sidelobes, and show the viability of full Mueller gridding and deconvolution for any telescope given high quality holographic measurements.

arXiv comment16 pages, 12 figures. Accepted for publication in AJ

References in corpus (19)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Astropy: A Community Python Package for Astronomy
• The Expanded Very Large Array -- a New Telescope for New Science
• Ionospheric Calibration of Low Frequency Radio Interferometric Observations using the Peeling Scheme: I. Method Description and First Results
• The non-coplanar baselines effect in radio interferometry: The W-Projection algorithm
• LOFAR facet calibration
• Correcting direction-dependent gains in the deconvolution of radio interferometric images
• Wide-field wide-band interferometric imaging:The WB A-Projection and hybrid algorithms
• Applying full polarization A-Projection to very wide field of view instruments: An imager for LOFAR
• Advances in Calibration and Imaging Techniques in Radio Interferometry
• The Atacama Large Millimeter Array (ALMA)
• Image Domain Gridding: a fast method for convolutional resampling of visibilities
• Calibration and Stokes Imaging with Full Embedded Element Primary Beam Model for the Murchison Widefield Array
• Primary beam effects of radio astronomy antennas -- II. Modelling the MeerKAT L-band beam
• Direction Dependent Corrections in Polarimetric Radio Imaging I : Characterizing the effects of the primary beam on full Stokes imaging
• Deep wideband single pointings and mosaics in radio interferometry - How accurately do we reconstruct intensities and spectral indices of faint sources?
• Direction Dependent Corrections in Polarimetric Radio Imaging II: A-Solver Methodology A low-order solver for the A-Term of the A-Projection algorithm
• Gain and Polarization Properties of a Large Radio Telescope from Calculation and Measurement: The John A. Galt Telescope
• The Pointing Self Calibration algorithm for aperture synthesis radio telescopes

Cited by in corpus (1)

• Tackling the Unique Challenges of Low-frequency Solar Polarimetry with the Square Kilometre Array Low Precursor: The Algorithm