Fundamental Imaging Limits of Radio Telescope Arrays

TL;DR

This paper develops a mathematical framework to understand the fundamental limits of radio telescope array imaging, considering noise, calibration errors, and source complexity, to guide better array design.

Contribution

It introduces a rigorous, signal processing-based framework to quantify the ultimate imaging performance limits of radio telescope arrays.

Findings

Defines the effective noise floor in radio imaging.

Analyzes the impact of calibration errors on image covariance.

Establishes the maximum number of sources tractable by self-calibration.

Abstract

The fidelity of radio astronomical images is generally assessed by practical experience, i.e. using rules of thumb, although some aspects and cases have been treated rigorously. In this paper we present a mathematical framework capable of describing the fundamental limits of radio astronomical imaging problems. Although the data model assumes a single snapshot observation, i.e. variations in time and frequency are not considered, this framework is sufficiently general to allow extension to synthesis observations. Using tools from statistical signal processing and linear algebra, we discuss the tractability of the imaging and deconvolution problem, the redistribution of noise in the map by the imaging and deconvolution process, the covariance of the image values due to propagation of calibration errors and thermal noise and the upper limit on the number of sources tractable by self calibration. The combination of covariance of the image values and the number of tractable sources determines the effective noise floor achievable in the imaging process. The effective noise provides a better figure of merit than dynamic range since it includes the spatial variations of the noise. Our results provide handles for improving the imaging performance by design of the array.