The Murchison Widefield Array:an SKA Precursor

Shep Doeleman - MIT HaystackFor the MWA Project

What is the MWA?• A wide-field, low-frequency imaging array • Optimized for wide FOV, high survey

speed• Frequency range 80-300 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

2 2~ 10humans kmρ − −

RFI Environment

Physical LayoutAntenna tile (~4m diam.)

clusters

Array (~1.5km diam.)

tile

Cluster (50-100m diam.)

node

Coax out

Tile beamformerFiber out

Central Processing

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Production Dual-Pol Antenna

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Tentative Configuration

Aperture Plane UV Plane

Point Spread Function

04/21/23

1024sig

A/DCoarse PFBSelect 30.72MHz 20 Tflops

192 fibers over 1-3km

32 single pol

524,288 sig pairs18 Tera CMACs10kHz resolution0.5 sec accumulate

160Gb/s

80-300MHz

2-10 Tflop

No FringeStopping

Ionospheric Calibration

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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

• 2010 - 2012 –Refinement and incremental expansion

• 2013 and beyond – Possible major expansion

Murchison Widefield Array: Design

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Murchison Widefield Array: SpecsFrequency rangeFrequency range 80-300 MHz80-300 MHz

Number of receptorsNumber of receptors 8192 dual polarization dipoles8192 dual polarization dipoles

Number of tilesNumber of tiles 512512

Collecting areaCollecting area ~8000 m~8000 m2 2 (at 200 MHz)(at 200 MHz)

Field of ViewField of View ~15°-50° (1000 deg~15°-50° (1000 deg22 at 200 MHz) at 200 MHz)

ConfigurationConfiguration Core array ~1.5 km diameter (95%, Core array ~1.5 km diameter (95%, 3.4’) +3.4’) +

extended array ~3 km diameter (5%, extended array ~3 km diameter (5%, 1.7’)1.7’)

BandwidthBandwidth 220 MHz (Sampled); 31 MHz 220 MHz (Sampled); 31 MHz (Processed)(Processed)

# Spectral channels# Spectral channels 10241024

Temporal resolutionTemporal resolution 8 sec8 sec

PolarizationPolarization Full StokesFull Stokes

Point source sensitivityPoint source sensitivity 20mJy in 1 sec (32 MHz, 200 MHz)20mJy in 1 sec (32 MHz, 200 MHz)

0.34mJy in 1 hr0.34mJy in 1 hr

Multi-beam capabilityMulti-beam capability 32, single polarization32, single polarization

Number of baselinesNumber of baselines 130,816 (VLA: 351, GMRT: 435, ATA: 130,816 (VLA: 351, GMRT: 435, ATA: 861 )861 )

Where and Why

04/21/23 Next Generation Heliospheric Imager Workshop, NSO, Sunspot

ρHumans ~ 0.003 km2

Murchison Widefield Array

1804/21/23 Next Generation Heliospheric Imager

Workshop, NSO, Sunspot

32 Tile system: Specs

Aperture plane uv plane

32 tiles, 4 nodes ∆t = 50 ms

Aeff = 550 m2 (~6% of MWA) 0 ~15’ @ 200 MHz

Bandwidth = 31 MHz 496 physical baselines

∆ = 10 kHz Max data rate ~12.7 Mvis/s (1TByte in ~2h45min)

MWA Current Status

A team is currently on site8 element interferometer to be set up by the end of April 0832 element interferometer by July 08

Major construction phase to begin shortly after that

04/21/23 Next Generation Heliospheric Imager Workshop, NSO, Sunspot

Murchison Widefield Array

Primary Science ObjectivesEpoch of ReionizationSolar, Heliospheric and Ionospheric ScienceTransients

Collaborating InstitutionsMIT Haystack, MKI, CfA (NSF Ast and Atm, AFOSR)7 Australian InstitutionsRaman Research Institute, India

~20 MUSD

04/21/23 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

04/21/23 Next Generation Heliospheric Imager Workshop, NSO, Sunspot

Key design considerations

• High dynamic range imaging• Calibrability

04/21/23 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