Atacama Large Millimeter/submillimeter ArrayExpanded Very Large Array

Robert C. Byrd Green Bank TelescopeVery Long Baseline Array

The Expanded Very Large Array

Rick PerleyNational Radio Astronomy Observatory

EVLAThe Expanded Very Large Array• The Expanded Very Large Array is a $90M

upgrade of the Very Large Array.– Project began in 2001, will be completed in 2012 – on

time, on spec, on budget.• The EVLA will multiply by orders of magnitude

the observational capabilities of the VLA. Key goals are:– Full frequency coverage from 1 to 50 GHz.– Up to 8 GHz instantaneous bandwidth.– New correlator with unprecedented capabilities– ~3 mJy (1-s, 1-Hr) point-source continuum sensitivity at

most bands.– ~1 mJy (1-s, 1 km/sec, 1 Hr) line sensitivity at most

bands.

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EVLA

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Overall EVLA Performance Goals• Providing orders of magnitude improvements in

performance!Parameter VLA EVLA Factor

Continuum Sensitivity (1-s, 1 hr.) 30 mJy 3 mJy 10

Maximum BW in each polarization 0.1 GHz 8 GHz 80

# of frequency channels at max. BW 16 16,384 1024

Maximum number of freq. channels 512 4,194,304 8192

Coarsest frequency resolution 50 MHz 2 MHz 25

Finest frequency resolution 381 Hz 0.12 Hz 3180

# of full-polarization spectral windows 2 64 32

(Log) Frequency Coverage (1 – 50 GHz) 22% 100% 5

EVLAEVLA Milestones• 26 of 28 antennas now converted to EVLA

standards. – All antennas converted by July 2010.

• VLA correlator to be shut down on January 11. • New EVLA correlator awakens early February.

• Wideband Interferometric Digital ARchitecture (WIDAR) correlator contributed by Canada

• EVLA ‘early science’ OSRO and RSRO programs begin March 2010 and continue through end of 2011.

• Full bandwidth (8 GHz) available on all antennas mid-2011.

• Receiver implementation completed end of 2012. 4

EVLA

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Full-Bandwidth Availability Timescale• During transition, L, C, and X band receivers are on all

antennas.

WIDAR Correlator

Arr

ay S

hutd

own

EVLAThe ‘WIDAR’ Correlator• A 10 petaflop special-purpose computer.

– Designed and built by Canadian HIA/DRAO.

• Major capabilities:– 8 GHz maximum instantaneous bandwidth, with full

polarization.– 16384 minimum, 4.2 million maximum frequency

channels– 64 independently tunable full polarization ‘spectral

windows’, each of which effectively forms an independent ‘sub-correlator’.

– Extensive special modes: pulsar gating/binning, phased array, VLBI-ready, burst modes, and more.

• Fundamental capabilities will be developed first, with specialty modes later.

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EVLAEarly EVLA Testing Results• A 12-antenna sub-array used to test WIDAR-0

prototype. • This test configuration provides:

– 8192 channels– Full polarization– Eight adjacent spectral windows

• Test observations in 1—2 and 18 – 26 GHz bands are shown on subsequent slides.

• Other early results and future capabilities presented tomorrow morning in talks by:– Aeree Chung : 347.01: EVLA View of HI Dwarfs in Leo

Ring– Steve Myers: 357.03: Capabilities of the EVLA for

Surveys7

EVLASpectral Windows Continuity

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•Eight continuous subbands, each of 128 MHz, spanning 1 – 2 GHz band.

1.024 GHz

Satellites

AircraftNavigation

Cellphones

• Single baseline, ampscalar average, showing RFI, but also extensive ‘empty space’. These are raw data, with no bandpass correction.

• Same data, vector average, showing how RFI is decohered over a few minutes integration.

GPS

EVLA3C147 Deep Field @ 1440 MHz• 12 antennas, 110 MHz

bandwidth, 6 hours integration

• Fidelity ~ 400,000:1• Peak/rms ~ 850,000:1 • The highest fidelity image

ever made with the VLA – using only a fraction of the upcoming capability!

• The artifacts are due to non-azimuthal symmetry in the antenna primary beams. – Illustrates the need for

advanced calibration/imaging software.

– Urvashi Rao (357.01D) 9

First Null Primary BeamHalf Power

EVLA

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Orion-KL Spectrum – 3 GHz Wide• Three short obs. of Orion, each 1024 MHz wide, with ~1.5

km/sec velocity resolution and 2.5” spatial resolution, show 31 strong lines. • From ammonia (NH3):

• 8 lowest meta-stable inversion transitions (J,K) = (1,1) to (8.8)

• (6,6) line from 15NH3 isotopologue, • the 4(1,4)-4(0,4) line from NH2D.• meta-stable (9,8) & (10,9) lines,• Two E/A doublets of methyl

formate: CH3CHO• OCS 2-1• Three lines from SO2

• Ten strong methanol maser lines from E-type series (J=2 – 11).

• One unidentified line• Numerous weak lines.

24072 channels

EVLAOrion-KL: Zooming in …

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• Left Side: The lowest 1.0 GHz, showing identifications.• Right Side: The two lowest meta-stable transitions,

showing blended hyperfine structure.

Two SO2 lines

EVLASpectra from the 128 x 128 x 24012 data cube

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Moment-0 ImageEnd to end processing done in CASA by Steve

Myers

Data Cube available at: http://science.nrao.edu/evla/projectstatus/inde

x.shtml

EVLAEarly Science Programs• Two early science programs: March 2010 through

December 2011. • Open Shared Risk Observing (OSRO):

– A ‘business as usual’ observing protocol. – Observers will access EVLA in same manner as current for

VLA. – Initial configuration provides 512 spectral channels with one

or two spectral windows of 128 MHz (maximum) each.• Resident Shared Risk Observing (RSRO):

– Must be resident in Socorro for at least 3 months.– Participants will have access to more extensive observing

capabilities. – Participants will assist NRAO staff in expanding capabilities– Observing time proportional to length of residency. – 27 proposals received on first call, 13 have been accepted.

• For details, see: – http://science.nrao.edu/evla/earlyscience/osro.shtml– http://science.nrao.edu/evla/earlyscience/osro.shtml

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EVLA

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WIDAR Growth: 2010+• Observational capabilities will be rapid thru 2010 - 11 • All initial observations will be with the ‘fundamental

homogeneous correlator setup’– All spectral windows adjacent, with same width &

channelization, arranged to maximize total bandwidth (BW) coverage

• Resident observers (RSRO Program) should have access to:– 2 GHz/polarization BW (all antennas) by mid-2010– 8 GHz/polarization BW (all antennas) by end of 2011. – Recirculation (increased spectral resolution) by late 2010– Independent spectral window tuning by early 2011– Flexible resource allocation (trading spectral windows for

more spectral resolution) by mid 2011

EVLASummary• EVLA ready for science observations with all

antennas and unprecedented new capabilities: Mar 2010

• Wide-band (full tuning range) receivers available on all antennas– Highest frequency bands (18 – 50 GHz): mid 2010– 4 – 8 GHz: end 2010– Remaining four bands: 2012

• Early Science opportunities: Mar 2010 - Dec 2011 – Basic modes via OSRO Program: You stay home– Advanced modes via RSRO Program: You come to

Socorro• RSRO Program access will include

– 2 GHz BW available on all antennas by mid 2010– 8 GHz BW available on all antennas by mid 2011 – Increasing spectral resolution and tuning flexibility

through 2010-11 – Specialty modes as implemented, guided by user

interest•

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