Murchison Widefield Array (MWA) : Design and Status

Divya Oberoi, Lenoid BenkevitchMIT Haystack Observatory

doberoi, benkev@haystack.mit.edu

On behalf of the MWA Project

Partner Institutions and Sponsors

What is the MWA?

• A low-frequency imaging array

– 80 – 300 MHz

• Wide Field of View (FoV)

– Array elements – arrays of dipoles

The design approachCollaborators

Logistics

Politics

RFI

Ionosphere

Wide FoV Calibration & Mapping

RFI

Ionosphere

Wide FoV Calibration & Mapping

Base

line

Leng

th

RFI

Ionosphere

Wide FoV Calibration & Mapping

RFI

Ionosphere

Wide FoV Calibration & Mapping

Shire of Murchison.Pop: 199Area: 41,173 km2 (NL: ~41,500 km2)(UK: ~244,820 km2)

Humans ~105 lower than MA, UK, NL

RFI

Ionosphere

Wide FoV Calibration & Mapping

Array Configuration

u-v coverage

Monochromatic snapshot Zenith pointing

Point Spread Function

3-4%

~0.3%-10.2%

Murchison Widefield ArrayFrequency 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%, 3.4’) Core array ~1.5 km diameter (95%, 3.4’) ++extended array ~3 km diameter (5%, extended array ~3 km diameter (5%, 1.7’)1.7’)

BandwidthBandwidth 220 MHz (Sampled); 30.72 MHz 220 MHz (Sampled); 30.72 MHz (Processed)(Processed)

# Spectral channels# Spectral channels 1024 (3072)1024 (3072)

Temporal resolutionTemporal resolution 8 s (0.5 s)8 s (0.5 s)

PolarizationPolarization Full StokesFull Stokes

Point source sensitivityPoint source sensitivity 20mJy in 1 s (30.72 MHz, 200 MHz)20mJy in 1 s (30.72 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 130816 (VLA: 351, GMRT: 435, ATA: 861)130816 (VLA: 351, GMRT: 435, ATA: 861)

Choice of Science Objectives

Key Features of Interest

• Magnetic field measurements in the corona and heliosphere via Faraday rotation observations – 1 source every 6-9 deg2

• Velocity, turbulence characteristics etc. via IPS– 32 independent beams and wide fields of view

• Location and evolution of shocks via imaging of Type II bursts– Very good monochromatic snap-shot imaging capabilities– Sufficient time and spectral resolution

32 Tile Prototype

Motivation Engineering test bedEnd to end signal/data path and system performance testingTraining data sets for calibration systemLearning to operate in the site conditionsEarly Science

Broadband spectrum

Orbcomm satellites

Defense satellite network

FM Band

A. Roshi, RRI

R. Wayth, CfA/Curtin Uni.

Puppis A, 159 MHz, 1.28 MHz (10 kHz), 24 elements

First Light Images from MWA prototype

Best image so farPictor A, 158.7 MHz

= 330 mJyChristopher Williams, MIT

• 7, 5min scans, spread over 6 hours• 1.28 MHz• 27 tiles• Crosses mark the location of sources of with flux > 2Jy (1420 MHz)• Dynamic Range 1000+

Status and Schedule• Analog hardware for 32T system in place• Digital hardware (correlator) deployment - June 09• 32T performance testing - 4Q 2009• End of build-out phase for the final system – 3-4Q 2010

• Science capabilities will slowly grow starting now

– Remote operations started

– Hardware correlator 30.72 MHz

– A strong possibility of an interim 128T array, while we build out to 512T.

Summary

• MWA - optimized for calibration and imaging challenges at low frequencies

• Needs of the key science applications and the instrument’s capabilities are very well matched

• Data flow from the prototype array has commenced• Busy schedule and exciting times ahead• Stay tuned…