A survey of spatially and temporally resolved radio frequency interference in the FM band at the Murchison Radio-astronomy Observatory

TL;DR

This survey provides a detailed, spatially and temporally resolved analysis of FM band radio frequency interference at the Murchison Radio-astronomy Observatory, crucial for future SKA observations.

Contribution

It is the first to categorize and analyze RFI signals at MRO with high temporal and spatial resolution, including reflections from aircraft, orbiting objects, and meteor trails.

Findings

Detected approximately forty thousand RFI events.

Categorized RFI sources including direct transmitters, aircraft reflections, and meteor trails.

Provided detailed RFI environment profile for the SKA site.

Abstract

We present the first survey of radio frequency interference (RFI) at the future site of the low frequency Square Kilometre Array (SKA), the Murchison Radio-astronomy Observatory (MRO), that both temporally and spatially resolves the RFI. The survey is conducted in a 1 MHz frequency range within the FM band, designed to encompass the closest and strongest FM transmitters to the MRO (located in Geraldton, approximately 300 km distant). Conducted over approximately three days using the second iteration of the Engineering Development Array in an all-sky imaging mode, we find a range of RFI signals. We are able to categorise the signals into: those received directly from the transmitters, from their horizon locations; reflections from aircraft (occupying approximately 13% of the observation duration); reflections from objects in Earth orbit; and reflections from meteor ionisation trails. In total we analyse 33,994 images at 7.92 s time resolution in both polarisations with angular resolution of approximately 3.5 deg., detecting approximately forty thousand RFI events. This detailed breakdown of RFI in the MRO environment will enable future detailed analyses of the likely impacts of RFI on key science at low radio frequencies with the SKA.