The Murchison Widefield Array

Realisation of a low frequency SKA Precursor: The Murchison Widefield Array

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Citation Tingay, Steven, et al. "Realisation of a Low Frequency SKA Precursor: The Murchison Widefield Array." Proceedings of Resolving The Sky - Radio Interferometry: Past, Present and Future, 17-20 April, 2012, Manchester, UK, Sissa Medialab, 2012.

Publisher Sissa Medialab

Version Final published version

Citable link http://hdl.handle.net/1721.1/121115

Detailed Terms http://creativecommons.org/licenses/by-nc-nd/4.0/ PoS(RTS2012)036 http://pos.sissa.it/ ayth, M. Waterson , T. Colegate, P.J. Hall, evens ce. ms J. Lonsdale, S.R. University, Perth, Australia University, Perth, Australia nbridge, USA USA ive Commons Attribution-NonCommercial-ShareAlike Licen ∗ [email protected] Copyright owned by the author(s) under the terms of the Creat c CSIRO Astronomy and Space Science, Australia R.J. Cappallo, B.E. Corey, B.B. Kincaid,McWhirter, E. A.E.E. Kratzenberg, Rogers, C. J.E. Salah,MIT A.R. Haystack Whitney Observatory, Westford, USA F. Briggs, B. McKinley The Australian National University, Canberra, Australia J.D. Bunton, L. deSouza, R. Koenig, J. Pathikulangara, J. St E-mail: R. Goeke, J.N. Hewitt, E. Morgan, R.AMIT Remillard, Kavli C.L. Institute for Willia Astrophysics and Space Research, Ca J.D. Bowman Arizona State University, Tempe, USA D. Emrich, S.M. Ord, T. Booler,D. B. Herne, Crosse, M.J. D. Lynch, Pallot, F. W. Schlagenhaufer,International Arcus S. Centre Tremblay, for R.B. Radio W Astronomy Research - Curtin D.A. Mitchell, R.J. Sault, R.L. Webster, J.S.B.The Wyithe University of Melbourne, Melbourne, Australia M.F. Morales, B.J. Hazelton University of Washington, Seattle, USA A. Wicenec, A. Williams ICRAR - University of Western Australia, Perth, Australia D. Barnes Swinburne University of Technology, Melbourne, Australia G. Bernardi, L.J. Greenhill, J.C. Kasper Harvard-Smithsonian Center for Astrophysics, Cambridge, International Centre for Radio Astronomy Research - Curtin S.J. Tingay Realisation of a low frequency SKAMurchison Widefield Precursor: Array The PoS(RTS2012)036 vani, R. ce. SKA Precursor, comprising brief discussion of the as-built w frequency arrays. The MWA rom approximately August 2012 tical completion of the MWA is ionisation; 2) studies of Galactic of the variable radio sky; and 4) n of recent science results from the iameter. The MWA is located at the ightness temperature of the diffuse the instrument, and a brief progress ervatory in the mid-west of Western ted surveys of the full sky visible to onosphere via propagation effects on Future - RTS2012 Wayth, Webster and Wyithe are affiliated with the ARC ive Commons Attribution-NonCommercial-ShareAlike Licen † redshifted 21 cm line of neutraland hydrogen extragalactic from processes the based epoch on of deep, re confusion-limi Australia, the selected home for thescience Phase goals 1 and include: Phase 1) 2 SKA detection lo of fluctuations in the br the array; 3) timesolar domain imaging astrophysics and characterisation through of exploration thebackground heliosphere radio and source i emission.MWA system, This highlighting paper several will novel focus characteristicsreport on of (as a of June 2012)expected in on November the 2012, with final commissioning construction commencingand f phase. operations commencing near Prac mid 2013. AMWA prototype brief instrument descriptio is given. The Murchison Widefield Array is a low frequency (80 - 300extraordinarily MHz) radio quiet Murchison Radioastronomy Obs 128 aperture array elements distributed over an area of 3 km d Speaker. Gaensler, Briggs, McKinsley, Mitchell, Tingay, Tremblay, ∗ † Copyright owned by the author(s) under the terms of the Creat c Centre of Excellence for All-sky Astrophysics (CAASTRO) April 17-20, 2012 Manchester, UK Resolving the Sky - Radio Interferometry: Past, Present and University of Sydney, Sydney, Australia M. Johnston-Hollitt Victoria University of Wellington, New Zealand D.L. Kaplan University of Wisconsin–Milwaukee, Milwaukee, USA D. Oberoi National Centre for Radio Astrophysics, Pune, India Subrahmanyan Raman Research Institute, Bangalore, India B.M. Gaensler A. Deshpande, T. Prabu, A. Roshi, N. Udaya-Shankar, K.S. Sri PoS(RTS2012)036 S.J. Tingay ). MeerKAT 2 ifferent frequency ranges perated, prototype instru- tre Array (SKA: [Dewdney et al. 2010]) ntenna technologies (MWA: er of generations of prototype mber of other instruments have . The MWA is sited at the MRO long with a second SKA Precur- 1 n a candidate SKA site) and are dmap technologies for the SKA et al. (2012)]. ed from the prototype array data eds). The combined MWA and sor is a recognised SKA technol- ompassed by the MWA at the low ern Australia and the Karoo region 008]; [Johnston et al. 2007]).te The t the SKA, the Murchison Radio- tereference in this area of Western ng Test Array (BETA ticular, the MWA explores the so- . The MWA 32 tile array also un- ual underpinnings of the MWA de- Netherlands [van Harlem et al. 2012]. e sky and therefore high sensitivity cess. The most notable of the SKA 2 tile prototype array ceased in late or SKA science [Carilli & Rawlings 2004]. al MWA instrument in early 2012. A radio interferometers and some of the elescope. [Lonsdale et al. (2009)] also ed for the SKA, with large numbers of dware and data processing elements, as der to demonstrate on-sky performance. 2 , a seven antenna array. For the MWA, a 32 tile test array oper- 3 Previously, [Lonsdale et al. (2009)] described the concept The MWA and ASKAP are complementary, in that they operate in d All three of the MWA, ASKAP and MeerKAT are planning, or have o While only three instruments have SKA Precursor status, a nu The Murchison Widefield Array (MWA) is the only Square Kilome http://public.ska.ac.za/meerkat http://www.atnf.csiro.au/projects/askap http://public.ska.ac.za/kat-7 1 2 3 is being preceeded by KAT7 ated for two yearshardware from as 2009, well allowing as the severaldertook assesment trials science-quality of of astronomical a MWA observations, system numb A in integration number or of science[Williams results et have al. been, 2012, or Oberoi et2011, will al. in soon 2011]. preparation be, for Operation report the offull start description the of of 3 the construction MWA science for goals the is fin given by [Bowman sign, the advantages of achallenges large-N, inherent small-D in architecture the for dataprovided processing brief for descriptions this of the type initial of planswell t for as MWA the har science goals for the MWA. due to the extremely low levelsAustralia, of particularly manmade within radio the frequency FM in end band of (87 its - operating 108 frequency range. MHz) enc (MWA: 80 - 300 MHz; ASKAP: 0.7aperture - 1.8 arrays GHz) and (tiles); employ differentASKAP ASKAP: a technology dishes specifications plus almost Phased[Dewdney et fully Array al. sample 2010] Fe at thecalled a roa large-N single and small-D radio array quietsmall concept location. that receiving will elements In be providing utilis par aover large wide fields, field equating of to high view survey on speed, a th key metric f SKA Pathfinder status (SKA technologyalso demonstrator feeding information but into not the o Pathfinders SKA in the design low and frequency regime costing is pro LOFAR, built in The ments. ASKAP is building the six antenna Boolardy Engineeri The Murchison Widefield Array 1. Introduction Precursor telescope at lowogy radio demonstrator frequencies. located An at SKAastronomy one Observatory Precur of (MRO) in the the Murchison two regionof sites of South West that Africa’s Northern will Cape. The hos sor, MWA is the sited at Australian the SKA MRO, a PathfinderMeerKAT (ASKAP: SKA Precursor [Johnston will et be al. located 2 at the South African si PoS(RTS2012)036 re 40 kHz × S.J. Tingay nalog beam- 10 kHz fine channels. A rture plane baseline distri- × d by CSIRO, which we share ed at: ber of design and construction ntenna, approximately a square nals from eight tiles into a single r-cooled equipment racks for our ed, and hence high power usage, oduce real-time calibrated images eivers meet here and each of the ignals with an 8-bit A/D converter, tiles. This paper will give a brief filters the two analog signals from ion of which will appear elsewhere y band. The receivers themselves optic links. One of our early design into 128 ar resolution imaging. This 2.25 Gbps stream of correlation most receiver locations so that future nd outputs its results in 768 l purpose graphical processing units pe array, and a brief report on current wideband analog outputs representing figuration as an antenna tile and analog ion, have been finalised. In particular d from a standard 240 V mains circuit, andscape such that no tile is more than ey et al. (2012)]). The final 16 tiles are 100 metre diameter core, with a further iles, or else support completely different cture at low incremental cost. The excess radial distribution. The inner part of the array 2 3 − r 1.28 MHz frequency channels which form a selectable, × 150 MHz. Sixteen of these antennas are configured as an apertu ∼ 4 grid (with spacing 1.1 m); their signals are combined in an a × The four science drivers for the MWA lead to a desire for an ape A host of practical considerations lead us to combine the sig About 5 km from the centre of the array lies a building provide Updates and news items for the MWA project are regularly post The MWA signal path starts with a dual-polarisation dipole a Since the [Lonsdale et al. (2009)] paper was published, a num former to provide coarse pointingorthogonal capability, X produces and two Y linear polarisations. Webeamformer. refer to this con bution which has a dense core and a smooth array on a regular 4 cross-multiply stage implemented in(GPGPUs) software processes, averages using in time genera and frequency space, a therefore has 50 antenna tiles uniformly62 distributed tiles over distributed a over a 1.5placed km on a diameter 3 circle km ([Beardsl diameter circle to optimise the highestreceiver; angul we thus deploy 16 receivers500 distributed metres over removed our l from itseach tile associated to receiver. a bandpass A ofand 80 receiver to digitally 300 MHz, filters Nyquist-samples the the s result into 24 channels over the 30.72 MHz bandwidth withproducts 0.5 s is resolution. then processed by the Real Time System (RTS) to pr usually but not necessarilyare contiguous, a 30.72 mixture MHz ofdigital high frequenc circuitry technology with and mechanical low, cooling. combiningand They send high-spe are out powere their digital datadecisions streams was to on provide three spare 2.1 power Gbps andinstrument fibre fibre development connections could to share our existing infrastru infrastructure could support a doubling of the array to 256 t instrumentation alongside the MWA facility. with the ASKAP project. Itsignal has processing power, EMI hardware. shielding, andcoarse The wate frequency data channels streams is from filtered all by 16 dedicated rec hardware The Murchison Widefield Array considerations, that were uncertainthe at originally the time envisaged of 512summary publicat tiles of has the been as-built MWA re-scoped system[Tingay overview, to et a al. full 128 (2012)], descript a summaryprogress of with results the from final the construction prototy of the MWA. http://www.facebook.com/Murchison.Widefield.Array 2. System overview of the as-built MWA metre of collecting area at PoS(RTS2012)036 S.J. Tingay d as a period d, in order to hen the Sun is blind source extraction tions and monitor system orms the correlator cross- data will be transmitted on een 2009 and 2011. The pri- te-wide services provided by uv panned the instantaneous fre- ture, including the reticulation sed the MWA prototype to ob- sign and implementation of the year period, to accommodate the Centre for SKA science in Perth, s of solar radio transients from the ase going from 32 to 128 tiles and r the prototype data, and used it to ms the coronal diagnostic capability ison of these sources with existing cations. As it turned out, the proto- s in this field. [Williams et al. 2012] e of the nature of radio observations ped. Selected results that are already follow the spatial, spectral, and tem- re and numerous short-lived, narrow- a. The data represented a significant ta to also be saved, to allow for the nce observations were supported with e publications derived from prototype ted detail. The rich variety of features iques for epoch of reionisation experi- e array system performance, wide field quency radio interferometers come on- sources at high significance and an ad- t and the 4 201.6 MHz and, though the observing period was characterise 3000 m baselines is likely to be dramatic, during the period w − ∼ diameter fields in the southern sky in the 110 MHz to 200 MHz ban ◦ 15’ angular resolution images of the two fields, performing a ∼ 300 m to ∼ [Oberoi et al. 2011] presented the first spectroscopic image The MWA project operated a 32 tile prototype instrument betw The MWA runs a monitor and control system toSupporting schedule the observa MWA instrument is the underlying infrastruc In a very important milestone paper, [Williams et al. 2012] u mary purpose of thevarious prototype MWA sub-systems. was In addition, to wherethe allow possible, prototype, scie the which iteration has of resultedtype in de was a far more number scientifically of capable than recentpublically we publi available could are have ho briefly reviewedarray here. data are A currently further in fiv preparation. prototype MWA, observed on 2010quency March band 27. 170.9 The observations s of fibre and power aroundCSIRO. the array and the connection to MRO si 3. Results from the 32 tile prototype array a dedicated 10 Gbps optical fibrewhere connection 15 to PB the of Pawsey data HPC storageMWA data capacity archive. has been reserved over a 5 health and parameters of use for data processing. of “low" to “medium" activity, oneband, broadband emission non-thermal featu emission features wereadvance evident in low in radio the frequency dat solarporal imaging, evolution enabling of us events to simultaneously andseen in in even unpreceden this very small amount ofof limited low MWAdata radio reaffir frequency emission andthat provides will an become early available glimps as theline next over generation the of low-fre next fewfrom years. The expected performance incre entering the peak of the solar cycle over the next few years. serve two 50 evaluate the performance of the prototype,ments, to and develop to techn make measurements ofdeveloped astronomical a foreground CASA-based calibration andproduce imaging pipeline fo using the resulting confusion-limited imagesditional to detect 871 655 lower significance sourcelow-frequency radio candidates. surveys was used A to assess compar the prototyp multiply. We have enabledpossibility the of post-observation ability processing. for The full RTS outpu visibility da The Murchison Widefield Array every 8 s. The RTS also runs on the same GPGPU machine that perf PoS(RTS2012)036 S.J. Tingay have been integrated and nce computing cluster of is cluster, along with the al- onstructed and placed at these totype array data, considerable ed in order to make way for the known as 2PiP developed by the I) commenced in early 2012, with leted, and power and fibre laid to e of the final instrument. For ex- tructed and installed on the ground La Plante & Greenhill(2012)]. The ns for the 128 tiles were surveyed s rotation, chromatic and asymmet- s where receivers will be placed on n the field hardware and the CSIRO o reticulate power and optical fibre. aminated by foreground subtraction. atistical distributions of point sources yed to the MRO starting in July 2012, of observation on two fields (900 and ocations of the final MWA and accu- e of the deepest surveys to date of this nisation power spectrum of redshifted e final system commenced in February vers went through extensive EMC test- hough we will only initially utilise 16 k was completed in June 2012 and all ct radio quiet regulations for equipment m for the MWA correlator. The correla- og was found to agree well with existing cture required to support the instrument. sion therefore exists, or else could be used 5 detection of the power spectrum along with slope σ In addition to the extraction of the science results from pro In parallel with the infrastructure work, accurate positio Receiver production at Poseidon Scientific Instruments (PS In late 2011, the MWA project took delivery of a high performa In early 2012, the 32 tile prototype array was de-commission low-frequency surveys in these regions ofderived the from sky Northern and Hemisphere with surveys; st itsky represents field on in the 110 MHz to 200 MHz band. work has been putample, into [Beardsley understanding et the al. (2012)] sciencerately examines performanc calculates the the planned array tile sensitivity l 21 to cm the emission. Epoch The ofrical calculation Reio baseline takes effects, into and account[Beardsley excludes synthesi et modes al. that (2012)] conclude will700 that be with hours), cont one the full MWA will season be capable of a 14 The Murchison Widefield Array analysis algorithms, and catalog quality. The source catal construction of the final 128 tile2012, system. initially Construction with of civil th worksPrimarily to this establish work the consisted infrastru Seven of trenches trenching radiating around from the a16 site central locations t “hub” on have these been trenches.concrete comp pads. The 16 Capacity locations existsreceivers are to for 128 the support tiles. site 32 Infrastructure receivers, capacityto alt for support expan other instrumentation.electrical and This data infrastructure connections wor havecentral been processing facility. completed betwee and marked in May 2012.locations in Ground May screens 2012 and for thescreens all 4,096 in 128 dipole June antennas tiles 2012. were were cons c the first receivers delivered in Marching, 2012. to These ensure first that recei their performance complies with the stri at a pace determined by the production process at PSI. fielded at the MRO. It is expected that receivers will be deplo 4. Description of construction progress for final MWA constraints. 24 IBM iDataPlex servers,ready each procured housing dedicated two hardware NvidiaSmithsonian and GPGPUs. Astrophysical a Observatory, forms Th data the capture platfor tor system GPU code, the “Harvard X-engine"IBM is hardware, described the by [Clark, FPGA hardware and firmware, and the GPU code PoS(RTS2012)036 S.J. Tingay for SKA Science in Perth ng the Phase 1 and Phase 2 nd the valuable experience of e active from near the end of ata store will include real-time essing hardware in the CSIRO 012, with science commission- otentially become a very impor- his point in time, all the MWA esponding to approximately 300 ompletion, with the Monitor and ed, the MWA will have access to y, with practical completion (full , and the Real-Time System (RTS) emporary installation to commence ioning team of 19 individuals from plements part of the correlator. n the MRO and Perth on disk, until ineering handover. As receivers are g pathfinder observations in this fre- completed, engineering and science en verified prior to installation at the ng months, as the facility is handed ignal path for a fraction of the system perational mode. The RTS will utilise l instrument as a single 128 tile array rays) reached in November 2012. Fol- port large-scale transfers. Data will be ioned to take advantage of an excellent stronomy. As the MWA project moves only large low frequency interferometer the 32 time prototype. r progressively installed in the field over ure. ng on a 500 TB storage facility based at nce data will be obtained even before the d in the field. Before our hardware can be 6 With good progress in the final construction phase of the MWA a Finally, software development for the project is coming to c With the SKA site decision now behind the community, assigni The installation of the correlator and other MWA signal proc Thus, with infrastructure, tiles, receivers and correlato Data from the MWA will be transported to the Pawsey HPC Centre Control system in the finalfully tested stages and of ready development for and integrationexcess with testing compute the capacity system on in the an IBM o iDataPlex cluster that im 5. Discussion SKA low frequency arrays totant the facility Australian during site, the SKA the pre-construction MWA phase. canat As p the the MRO, the experience gained by undertaking challengin a data store that willdays grow of to MWA 15 observing at PB maximum overimages data a as well production five as year rate). visibility period The data (corr d for reprocessing in the fut the 32 tile prototype instrument behindfacility, us, located we in are well a posit prime regioninto for an low frequency initial radio commissioning a phase,10 institutions with over a 4 science countries, it commiss point is of likely practical that completion good is reached scie at the end of 2012. iVEC. Later in 2013, as the Pawsey Centre is fully commission commissioning using the infrastructure previously use for via a dedicated 102012. Gbps network. Initial commissioning data Thisthe may network network be link is transported becomes expected active betwee at tostored sufficient capacity in b to an sup archive in Perth, initially during commissioni integrated in the CSIRO building, we have the capacity for a t the next few months, engineering commissioning of the full s MRO. central processing facility isover expected from to the occur MRO insignal construction processing the hardware contractors comi will to be installed CSIRO. and After integrate t (32 tiles at aing time) of can these commence 32 from tileprogressively approximately partial fielded August arrays and 2 commencing more followingcommissioning tiles eng have will their proceed signal withinstrument paths 32 installed and tile commissioned segments as 4 oflowing x practical the 32 tiles completion, arra sub-ar final commissioningcan of commence the in ful early 2013. The Murchison Widefield Array tested in the laboratory environment and performance has be PoS(RTS2012)036 S.J. Tingay st effect, could be a sub- RO, to data storage in Perth. Ef- l owners of the Observatory site. vide this excess infrastructure to oximately 10 spare water cooled cation activities. Valuable experi- ency instrumentation. Finally, and ld be possible to correlate the SKA tions existing to 16 locations in the unding agencies in each of the four ment that will eventually host SKA ry rapid and flexible deployment of s and the MWA tiles, to the mutual "SKA Phase 1: Prelimninary System s much power and data infrastructure of SKA low frequency antennas, the y on a 10 Gbps data link from the MRO matters of maintaining a low frequency ne for the SKA pre-construction phase tion onal MWA tiles. Such a situation would nhill 2012, arXiv 1107.4264v2 htm 2, New Astronomy Rewiews, Vol. 48, ed 1 EE, 97(8), 1497 204.3111 7 Submitted to ApJ Description", www.skatelescope.org/pages/page_memos. Elsevier We acknowledge the Wajarri Yamatji people as the traditiona Thus, the connection between the MWA and SKA low, if used to be [Johnston et al. 2007] Johnston, S.[Lonsdale et et al. al. 2007, (2009)] PASA, 24, 174 Lonsdale, C.J. et al.2009, Proc. IE [Williams et al. 2012] Williams, C.L. et al. 2012, [Johnston et al. 2008] Johnston, S. et al. 2008, Ex.A., 22, 15 [Oberoi et al. 2011] Oberoi, D.[Tingay et et al. al. 2011, (2012)] ApJ, 728, Tingay, L27 S.J. et[van al. Harlem 2012, et PASA al. submitt 2012] van Harlem, M. et al. 2012, in prepara [Bowman et al. (2012)] Bowman, J.[Carilli et & al. Rawlings 2012, 2004] PASA submitted eds: Carilli, C. & Rawlings, S. 201 Support for the MWA comes fromMWA the consortium partner countries. institutions and f References [Beardsley et al. (2012)] Beardsley, A. et al. 2012, arXiv:1 stantial advantage in realising whatand is Phase 1 an construction. ambitious timeli Acknowledgments ence will be gained in anarray operational sense, in in the the environment practical identifiedperhaps with most importantly, future the SKA final MWA low has available frequ than twice a is required to supportthe the SKA 128 low consortium, tile consisting array. of:field; The power connection MWA and can to data pro connec the CSIROracks 160 to dB accommodate shielded signal processing room, equipment; with capacit to appr iVEC/Pawsey in Perth. Thus,MWA for can prototyping offer small a arrays ready-to-use signalfective path use from of the the field excess at MWASKA the infrastructure low M could prototype allow instrumentation a at the ve Phase MRO, 1 in and the Phase environ 2 lowlow frequency prototype arrays. antennas Furthermore, against it the wou well-testedlikely and allow operati an improved calibrationbenefit of of both both the projects. SKA antenna The Murchison Widefield Array quency range will inform SKA low frequency design and specifi [Clark, La Plante & Greenhill(2012)] Clark, La Plante & Gree [Dewdney et al. 2010] Dewdney, P.. et al. 2010, SKA Memo #130,