Murchison Widefield Array (MWA) -- Low Frequency Demonstrator (LFD)

The Murchison Widefield Array (MWA) is an innovative widefield low-frequency radio telescope sited in radio-quiet Western Australia. Operating in the frequency range from 80 MHz to 300 MHz, key projects are 21cm cosmology during the Epoch of Reionization, transient radio sources, and ionospheric and heliospheric studies. The instrument is versatile, and many other studies in Galactic and extragalactic radio astronomy are anticipated.

MIT/MKI is a founding member of the MWA Consortium, made up of institutions in the United States, Australia, India, and New Zealand. The U.S. archive for sky-imaging data, with a focus on enabling 21cm cosmology, is located at MKI. The MWA is currently being commissioned, and early operations will commence in July 2013.

The goal of the Murchison Widefield Array (MWA), formerly known as the Mileura Widefield Array, is to develop powerful new capabilities for radio astronomy and heliospheric science at frequencies from 80 to 300 MHz, optimized for extremely wide fields of view and unprecedented sensitivity at those frequencies. The MWA has specific scientific goals , and is underway as an international project led by the MIT Haystack Observatory with strong collaboration from the MIT Kavli Institute for Astrophysics and Space Science, the Harvard-Smithsonian Center for Astrophysics, a number of Australian universities and research institutions, and the Raman Research Institute in India.

MWA characteristics -- The MWA will consist of 8000 dual-polarization dipole antennas optimized for the 80-300 MHz frequency range, arranged as 512 "tiles", each a 4x4 array of dipoles. An illustration of the planned array deployment is shown above together with a photograph of one of the tiles.

The array will have no moving parts, and all telescope functions including pointing will be performed by electronic manipulation of dipole signals, each of which contains information from ~4 steradians of sky centered on the zenith. Each tile will perform an analog beamforming operation, narrowing the field of view to a fully steerable ~25 degrees at 150 MHz. The majority of the tiles (496) will be scattered across a roughly 1.5 km core region, forming an array with very high imaging quality, and a field of view of several hundred square degrees at a resolution of several arcminutes. The remaining 16 tiles will be placed at locations outside the core, yielding baseline distances of about 3 km to allow higher angular resolution for solar burst measurements. FPGA-based massively parallel digital hardware will select and condition a 32 MHz instantaneous bandwidth, and perform cross-correlation and digital array beamforming. Software for array calibration, as well as to support specific scientific goals, will be developed. Summaries of the MWA specifications and technical design is provided under Technical Design.

MWA science -- There are two driving science goals of the MWA. First, the MWA is designed to detect and characterize redshifted 21cm emission from the Epoch of Reionization. Such a result would be of profound cosmological significance and broad interest. Second, the MWA will allow high-precision remote sensing the heliosphere via measurement of radio propagation effects such as Faraday rotation and interplanetary scintillations, and it offers the prospect of constraining the magnetic field properties of coronal mass ejections, with associated benefits for space weather prediction.

As a third stated science goal to be sought on a best effort basis, the MWA will conduct a search for transient radio emission that is 6 orders of magnitude more sensitive than any previous work, yielding a variety of scientific opportunities. In addition, as a recent outgrowth of interest in the science community, the MWA will be able to make observations that contribute to pulsar research, measurement of interstellar medium properties, and the study of radio recombination lines. Moreover, by virtue of the need to calibrate the array for ionospheric effects, the MWA is expected to yield interesting and useful information about the Earth’s ionosphere on short time scales and small spatial scales.

The above science objectives are outlined under MWA Science. In order to promote, coordinate and facilitate the achievement of these science objectives and engage as broad a community involvement as possible, science collaborations associated with the major MWA science applications have been formed. References can be found under each of the MWA science topics.

MWA Location -- The sensitive observations that need to be made by the MWA to accomplish its science objectives require deployment of the array in a region where radio frequency interference (RFI) is mostly absent. This is the primary reason that the MWA is being constructed in the sparsely populated outback of Western Australia which was identified to be an exceptionally radio quiet area based on RFI measurements conducted at the Mileura station in the Shire of Murchison Preserving this radio quiet environment for the MWA also drove the decision in 2007 to move the array site roughly 80 km to the southwest from Mileura, within the Murchison Radio Observatory. Activity from the transport of ore from nearby mines would have jeopardized the radio quiet environment for the MWA at Mileura.

MWA linkages -- The MWA, a $10M-class instrument, will share site infrastructure in Murchison and array signal processing technology with the Australian Square Kilometer Array Pathfinder (ASKAP). The MWA itself is also considered a pathfinder for the international SKA effort, concentrating on the low frequency range of the SKA specifications. In the long term, consideration is being given to linking the MWA and ASKAP under one operational umbrella, but the near-term goal for MWA is to demonstrate the array technology at 80-300 MHz and accomplish the important science goals. The current phase of the MWA development covers the four-year time period from June 2006, when the project was formally initiated, to June 2010. Support for the MWA development comes from federal sources and institutional partners within the US, Australia and India.