The Murchison Widefield Array: From Commissioning to Observing

The Murchison Widefield Array: From Commissioning to ObservingD. Oberoi1,2, I. H. Cairns3, L. D. Matthews2 and L. Benkevitch2 on behalf of the MWA Collaboration

1 National Centre for Radio Astrophysics, TIFR, India2 MIT Haystack Observatory, USA3 School of Physics, Univ. of Sydney, Australia OutlineMurchison Widefield Array An introductionCurrent status and near term plansSome recent results from the MWAThe Murchison Widefield ArrayLow radio frequency interferometer (80-300 MHz)Key Design ConsiderationsExploit the advances in Digital Signal Processing and affordability of computing.Emphasis on quality calibrationOptimize the design for carefully chosen science targetsSimplify the problem to the extent possibleKey Design FeaturesLarge N (no. of interferometer elements)Compact footprint (max baseline ~3 km)Operation at higher end of the low radio frequency rangeRadio quiet location - Western Australian OutbackHumans ~ 4x10-3 humans km-2

3MWA: Key Science ProjectsEpoch of Reionization21cm hyperfine transition line of neutral hydrogen, red-shifted to frequencies below 200 MHzFlagship science application, but very challengingGalactic and Extra-galactic ScienceConfusion limited all-sky survey with full polarimetry and good spectral resolutionTime domain astrophysicsKnown and not yet known transientsSolar, Heliospheric and Ionospheric ScienceSpectroscopic solar imagingIPS and Faraday rotation studies of the HeliosphereIonospheric propagation effects

AOGS, Brisbane, June 2013

This should give people a good idea of the overall structure of the array. It basically builds up the array from the dipoles to the tiles to the nodes and the entire array. Though the array design here does not show it, the array will include 16 tiles outside the 1.5 km dia circle. The primary motivation for these tiles is to increase the resolution of the array to make it more useful for solar imaging. It might be worth mentioning it to this audience. BTW, to give you a feel for the background picture, the breakaway you see is almost aligned NS and is ~260m in length. The MWA site is due East of the breakaway and the region being considered for core is probably a little outside the edge of the image.5

X Axis spans 30.72 MHz (~140-170 MHz); Y Axis spans ~10 minMWA: uv coverage

Very Large ArrayNM, USA

351 baselines27 elements

8128 baselines128 elementsMWA: Current StatusInstrument re-scoped to 128 tiles (~early 2011)

Status as of June 2012Site infrastructure Site survey for marking tile locations and trench paths Trenching Laying power and optical fiber cables Building receiver pads Hardware installation Tiles - all 128 Beamformers all 128AOGS-AGU Joint Assembly, Singapore August 2012Aug. 2012, AOGSMWA: Current StatusCommissioning Period (June 2012 June 2013) Test and commission the array in 5 groups of 32 tiles each (June 12 Dec 12) Install the 128T correlator to run the entire array as a single instrument Commission the 128T as a single instrument Commissioning report accepted on June 20, 2013 at MWA Project meeting in Seattle, WA.Formal end of the commissioning periodOne year period of shared risk observing starts Jul 2013Jul-Dec 2013 Open only to MWA Project membersJan-Jun 2014 Significant amount of Open Skies observing time

AOGS, Brisbane, June 2012MWA: Solar Observations ProposalLead by Cairns and Oberoi Unbiased solar observingIn-depth investigations concentrate disproportionately on what is deemed to be interesting.Exploring new phase space discovery potential avoid application of any a-priori bias 30 hours (19 TB)1 hr/day for a month, at the same UT slotSame observing mode (12 chunks of 2.56 MHz distributed from 80 to 300 MHz); 1s, 40 kHz resolutionObservations for Interplanetary Scintillation (IPS), Ionospheric Scintillation, satellite radio beacons all require high time resolution data (~20ms) voltage beamformer to provide this is currently under development expect to conduct proof-of-principle observations using Directors Discretionary Time

GRANTEDCommissioning Highlights

Andrea Offringa (ANU) and the MWA Commissioning Team Commissioning HighlightsSouthern Galactic Plane Mosaic Ben McKinley (ANU), Natasha Hurley-Walker (Curtin), Randall Wayth (Curtin) and the MWA Science Commissioning Team

Commissioning Highlights: Solar Imaging

16 May, 201304:15:02 UT

0=153.905 MHz=640 kHz

t=1 second

Imaging Dynamic Range ~1500

Radio Movie

16 May, 201304:11:04 04:16:00 UT

0=153.905 MHz=640 kHz

t=1 second

Imaging Dynamic Range ~1500

Spatial Variability of Radio Emission

20%70%250%600%15ConclusionsCommissioning successfully completed on schedule.Shared risk observing commences next month.MWA is exceptionally well suited for solar imaging - represents the state-of-the-art for the high dynamic range, high fidelity imaging at low radio frequencies.

Open Skies policy - observing proposals from the community are invited for period starting Jan 2014.Visit http://www.mwatelescope.org for more information

If you would like to get involved div@ncra.tifr.res.in (Divya Oberoi)Baselines and u-v plane

The u-v plane, except that units on the axes should have been , not lengthNBaselines = N(N-1)/2(uij, vij)(-uij,-vij)u () v ()17

25 Sep, 201104:08:50 04:18:47 UT

0=152.3 MHz=80 kHz

t=1 second

Imaging Dynamic Range ~5500