The Murchison Widefield Array: an SKA Precursor Shep Doeleman - MIT Haystack For the MWA Project

What is the MWA? A wide-field, low-frequency imaging array Optimized for wide FOV, high survey speed Frequency range MHz: Sample RF Three key science goals – Epoch of Reionization – Solar, Heliospheric and Ionospheric – Radio Transients Designed to exploit RFI-quiet site in Western Australia

The Partnership Massachusetts Institute of Technology – Haystack Observatory (Project Office) – Kavli Institute Harvard SAO CSIRO (via synergy with ASKAP) UMelbourne, Curtin, ANU (founding partners) USydney, UTasmania, UWA, and others,... Raman Research Institute, India Government of WA 3

Murchison

RFI Environment

Physical Layout

Production Dual-Pol Antenna 8

Tentative Configuration Aperture Plane UV Plane

Point Spread Function 6/28/2015

1024 sig A/D Coarse PFB Select 30.72MHz 20 Tflops 192 fibers over 1-3km 32 single pol 524,288 sig pairs 18 Tera CMACs 10kHz resolution 0.5 sec accumulate 160Gb/s MHz 2-10 Tflop No Fringe Stopping

Ionospheric Calibration

MWA as SKA Precursor Large N – Array configuration – Large data transport flow – Large multiplier for all processing – Correlator architecture – Calibration algorithms: real time – Cannot store raw data Broad Science Case – Wide Field by design: transients – New analysis algorithms: EOR statistics – Links with solar, space weather community Remote Site International Project

Schedule September 08 to March 09 –32-tile system: as of yesterday 16 tiles fully functional (w/ bf and rx). –Progressive testing of production hardware systems –Milestone for funds release, June 09 April 09 to December 09 – Buildout to ~256 tile system – In-depth testing, refinement of algorithms January 2010 to June 2010 – Complete buildout to 512 tiles – Initiate key science investigations –Refinement and incremental expansion 2013 and beyond – Possible major expansion

Murchison Widefield Array: Design 15

Murchison Widefield Array: Specs Frequency range MHz Number of receptors 8192 dual polarization dipoles Number of tiles 512 Collecting area ~8000 m 2 (at 200 MHz) Field of View ~15°-50° (1000 deg 2 at 200 MHz) Configuration Core array ~1.5 km diameter (95%, 3.4’) + extended array ~3 km diameter (5%, 1.7’) Bandwidth 220 MHz (Sampled); 31 MHz (Processed) # Spectral channels 1024 Temporal resolution 8 sec Polarization Full Stokes Point source sensitivity 20mJy in 1 sec (32 MHz, 200 MHz) 0.34mJy in 1 hr Multi-beam capability 32, single polarization Number of baselines 130,816 (VLA: 351, GMRT: 435, ATA: 861 )

Where and Why 6/28/2015 Next Generation Heliospheric Imager Workshop, NSO, Sunspot  Humans ~ km 2

Murchison Widefield Array 18 6/28/2015 Next Generation Heliospheric Imager Workshop, NSO, Sunspot

32 Tile system: Specs Aperture plane uv plane 32 tiles, 4 nodes∆t = 50 ms A eff = 550 m 2 (~6% of MWA)  MHz Bandwidth = 31 MHz496 physical baselines ∆ = 10 kHz Max data rate ~12.7 Mvis/s (1TByte in ~2h45min)

MWA Current Status  A team is currently on site  8 element interferometer to be set up by the end of April 08  32 element interferometer by July 08  Major construction phase to begin shortly after that 6/28/2015 Next Generation Heliospheric Imager Workshop, NSO, Sunspot

Murchison Widefield Array  Primary Science Objectives Epoch of Reionization Solar, Heliospheric and Ionospheric Science Transients  Collaborating Institutions MIT Haystack, MKI, CfA (NSF Ast and Atm, AFOSR) 7 Australian Institutions Raman Research Institute, India  ~20 MUSD 6/28/2015 Next Generation Heliospheric Imager Workshop, NSO, Sunspot

MWA Science Goals Epoch of Reionization – Power spectrum – Strömgren spheres Solar/Heliospheric/Ionospheric – Faraday rotation, B-field of CME’s – Interplanetary Scintillation – Solar burst imaging Transients – Deep blind survey – Light curves (field and targeted) – Synoptic surveys Other – Pulsars – ISM survey – Recombination lines – Etc.

The Epoch of Re-ionization After ~300,000 years electrons and protons combine to form hydrogen After ~1 billion years stars and quasars ignite, radiation splits hydrogen into protons and electrons. In between are the Dark Ages

Why is low freq radio astronomy suddenly so hot? Huge advances in digital hardware  affordability of capable instrumentation Enormous increase in affordability of computing (considering a few Tflops machine for MWA) Considerable and continuing effort in development of calibration algorithms and techniques 6/28/2015 Next Generation Heliospheric Imager Workshop, NSO, Sunspot

Key design considerations High dynamic range imaging Calibrability 6/28/2015 Next Generation Heliospheric Imager Workshop, NSO, Sunspot Large number of interferometer elements Full cross-correlation architecture Full field-of-view imaging Compact array foot print

MWA Data/Computation Rates Sampler output –1024 x 660 MHz x 8 bits = 5.3 Terabits/sec Coarse Polyphase filterbank – Performed on full data rate in real time – Processing done by 512 Xilinx SX-35 FPGAs – Of order 20 Tflops, massively parallel Post-filterbank –Aggregate rate transmitted over fiber: 330 Gb/s –Transmission distance = 1 to 3 km