The MWA Site in Western Australia

The MWA is located within the Murchison Radioastronomy Observatory (MRO), defined as a region within a 70 km radius circle in the Shire of Murchison in Western Australia (WA). The above-referenced URL of the University of Western Australia also contains panoramic images of the MRO site. An illustrative photograph of the site that typifies the area is given here.

The MWA site is over 200 km inland from the western Australian coast, and approximately 300 km from the small coastal city of Geraldton which lies a few hundred kilometers north of Perth. The target region is extremely sparsely populated, and is characterized by fairly flat, sparsely vegetated, semi-arid terrain criss-crossed by shallow washes and watercourses. The ground is rough in places, but readily workable. The necessary dedicated infrastructure is under development by Australian institutions and governmental agencies to support the astronomical projects.

Particular strengths of the Murchison area for siting the MWA include:

• Excellent sky access, with the Galactic Center and the Magellanic Clouds reaching high elevations.
• Extremely low levels of RFI, with excellent prospects for maintenance of these low levels in the long term, through the establishment of a radio-quiet zone.
• Planned dedicated infrastructure for radio astronomical arrays, with the attendant expectation of low, predictable operational costs.
• Reasonable flexibility on the location of the tiles offering good prospects for configuration optimization. This is a consequence of the negligible population density and lack of physical impediments such as mountains or bodies of water.

Radio Frequency Environment

The MRO will be protected from developments that may cause radio interference through a combination of special WA State legislation and exiting Federal legislation administered by the Australian Communications and Media Authority. In addition to the MWA, the MRO will be home to the Australian SKA Pathfinder (ASKAP) and is the proposed Australian site for the international Square Kilometer Array (SKA). The RFI conditions are anticipated to be similar to those found at Mileura where a survey was previously conducted at various frequencies within the MWA band [110-250 MHz and 90-110 MHz (FM-band)].

Relevant measurements were also made across the MWA band from experiments conducted with MWA prototype tiles during an early deployment phase at the Mileura station (Bowman et al. 2007). Additional RFI level measurements are on-going and are expected to yield similar results.

Examples of the RFI measurements made during the early deployment prototype experiments using the MWA tiles are shown below. The left panel shows the received power in four frequency bands, each spanning 4 MHz, with an integration time of 1 hour. The spectra are exceptionally quiet with no significant external sources or self-generated RFI, including in the FM band at 102 MHz. The right panel presents the power at 187 MHz after a deep integration of 10 hours, showing that the power follows the expected t½ slope and indicating the absence of instrumental systematic errors.