Real-Time Calibration of the Murchison Widefield Array

TL;DR

This paper presents a real-time calibration and imaging system for the Murchison Widefield Array, demonstrating its effectiveness with simulated data and scalability for future low-frequency radio arrays.

Contribution

It introduces a real-time peeling-based calibration method for the MWA, capable of handling high data rates and various ionospheric conditions, scalable to larger arrays.

Findings

The algorithm works with strong galactic emission.

It performs well under different ionospheric conditions.

It scales efficiently with increasing number of antennas.

Abstract

The interferometric technique known as peeling addresses many of the challenges faced when observing with low-frequency radio arrays, and is a promising tool for the associated calibration systems. We investigate a real-time peeling implementation for next-generation radio interferometers such as the Murchison Widefield Array (MWA). The MWA is being built in Australia and will observe the radio sky between 80 and 300 MHz. The data rate produced by the correlator is just over 19 GB/s (a few Peta-Bytes/day). It is impractical to store data generated at this rate, and software is currently being developed to calibrate and form images in real time. The software will run on-site on a high-throughput real-time computing cluster at several tera-flops, and a complete cycle of calibration and imaging will be completed every 8 seconds. Various properties of the implementation are investigated using simulated data. The algorithm is seen to work in the presence of strong galactic emission and with various ionospheric conditions. It is also shown to scale well as the number of antennas increases, which is essential for many upcoming instuments. Lessons from MWA pipeline development and processing of simulated data may be applied to future low-frequency fixed dipole arrays.