The low-frequency environment of the Murchison Widefield Array: radio-frequency interference analysis and mitigation

TL;DR

This paper analyzes the radio-frequency interference environment of the Murchison Widefield Array, presents an automated RFI detection method, and offers recommendations to improve RFI mitigation for future radio telescopes like the SKA.

Contribution

It introduces an automated RFI detection strategy for the MWA, provides RFI statistics, and offers design recommendations for RFI mitigation in next-generation telescopes.

Findings

RFI detection removes 1.1% of data

Digital TV RFI occurs 3% of the time

MWA's remote location results in a cleaner RFI environment

Abstract

The Murchison Widefield Array (MWA) is a new low-frequency interferometric radio telescope built in Western Australia at one of the locations of the future Square Kilometre Array (SKA). We describe the automated radio-frequency interference (RFI) detection strategy implemented for the MWA, which is based on the AOFlagger platform, and present 72-231-MHz RFI statistics from 10 observing nights. RFI detection removes 1.1% of the data. RFI from digital TV (DTV) is observed 3% of the time due to occasional ionospheric or atmospheric propagation. After RFI detection and excision, almost all data can be calibrated and imaged without further RFI mitigation efforts, including observations within the FM and DTV bands. The results are compared to a previously published Low-Frequency Array (LOFAR) RFI survey. The remote location of the MWA results in a substantially cleaner RFI environment compared to LOFAR's radio environment, but adequate detection of RFI is still required before data can be analysed. We include specific recommendations designed to make the SKA more robust to RFI, including: the availability of sufficient computing power for RFI detection; accounting for RFI in the receiver design; a smooth band-pass response; and the capability of RFI detection at high time and frequency resolution (second and kHz-scale respectively).