Generalized Redundant Calibration of Radio Interferometers

TL;DR

This paper introduces a generalized redundant calibration algorithm for radio interferometers that can handle non-idealities in array configurations, but faces challenges in parameter interpretability.

Contribution

It proposes a new calibration method replacing single gains with multiple gains per antenna, extending redundancy calibration to more realistic array conditions.

Findings

Successfully fits data from approximately redundant arrays with errors

Models parameters are difficult to interpret in terms of physical quantities

Discusses limitations and potential extensions of the algorithm

Abstract

Redundant calibration is a technique in radio astronomy that allows calibration of radio arrays whose antennas lie on a lattice by exploiting the fact that redundant baselines should see the same sky signal. Because the number of measured visibilities scales quadratically with the number of antennas but the number of unknowns describing the individual antenna responses and the available information about the sky scales only linearly with the array size, the problem is always over-constrained as long as the array is big and dense enough. This is true even for non-lattice array configurations. In this work we study a generalized algorithm in which a per-antenna gain is replaced with a number of gains. We show that it can successfully fit data from an approximately redundant array on square lattice with pointing and geometry errors, but that the models parameters are difficult to link to the quantities of interest. We discuss the parameterization, limitations, and possible extensions of this algorithm.