1

National Radio Astronomy Observatory

EVLA Status--

Jim Ulvestad, for Mark McKinnon, Rick Perley, and the EVLA Team

2

EVLA Project Overview• The Expanded Very Large Array is a major upgrade of the

Very Large Array.

• The fundamental goal is to improve all the observational capabilities of the VLA -- except spatial resolution -- by at least an order of magnitude.

• The Project began in 2001, and will be completed in 2012, on time, on spec, and on budget.

• Limited ‘Shared Risk’ Observing will begin late in 2009.

• Observing Capabilities will rapidly rise through 2010 – 2012.

3

The Eight Cassegrain Frequency Bands

Band

(GHz)

Tsys/

(goal)

Tsys/

(achieved)

# IF IF BW

(GHz)

Digitization (#GS/s @ #bits)

1-2 L 58 50 -- 65* 2 1 2 @ 8

2-4 S 42 TBD 4 1 2 @ 8

4-8 C 44 50 – 60* 4 2 4 @ 3

8-12 X 53 45 -- 60+ 6 2 4 @ 3

12-18 Ku 68 TBD 8 2 4 @ 3

18-26.5 K 115 70 -- 90 8 2 4 @ 3

26.5-40 Ka 135 130# 8 2 4 @ 3

40-50 Q 215 250 -- 400# 8 2 4 @ 3

* Without the new wideband OMT+ The current VLA receiver# Will improve after optics alignment and panel adjustments

Showing the performance and characteristics of the eight bands

4

EVLA Feed System• All eight Cassegrain feeds are compact

or linear taper corrugated horns with ring loaded mode converters.

• Horns are large (7 aperture) because the subreflector is small.

1 – 2 GHz2 – 4

4 - 8

8 - 12

12 - 18

18 - 2726 - 40

40 – 50

5

Antenna Conversions

• Conversion Activities:– Add new feed cone to vertex room– Add new HVAC, power, and

cryogenics distribution systems– Add IF, samplers, DTS electronics– Antennas emerge with:

• Interim 20cm, 6cm receivers• Old 3.6cm receivers, • Final 1.3cm, 7mm receivers

– S, Ka, new X, Ku bands to be installed later

• All 28 VLA antennas are being converted to modern standards at the rate of 5 to 6 per year.

• Conversion on track for completion in Q3 2010• 18 EVLA antennas now back observing.• 19th and 20th antennas are undergoing conversion

6

Receiver Outfitting Details

• Final K (18 – 26.5 GHz), Q (40 – 50 GHz) bands installed on converted antennas.– Full frequency coverage, and full sensitivity available NOW on all

converted antennas.

• Interim L (1 – 2 GHz), C (4 – 8 GHz) bands are on all converted antennas. – Full tuning range accessible, but with compromised sensitivity

and polarization outside traditional VLA frequency ranges.– new wideband OMT design now completed, retrofitting in

progress.

• Ka (26.5 – 40 GHz) band prototypes field tested – meet all requirements. Accelerated outfitting now underway.– Six antennas currently equipped.

7

Full-Band Tuning & Sensitivity Availability

8

EVLA Imaging of HI Absorption at 1082 and 1139 MHz

• Observations made in daytime, in D-configuration.• About 25% of data flagged for RFI of some sort. • Used 15 ‘interim’ EVLA antennas. • Sensitivity will increase dramatically with new OMT.

EVLA only1082 MHz

EVLA and VLA1139 MHz

1127-145 1413+135

9

Other Unique EVLA Projects now Scheduled

• Users have noted the increased frequency access:– 32 proposals accepted for C-band frequencies

outside the VLA 4.5 – 5.0 GHz window.• Galactic science proposals involve methanol, excited OH,

and formaldehyde masers in star forming regions.• Extragalactic science involves H2O masers near z = 2.

– 9 proposals accepted for expanded K-band coverage.• Science goals mostly involving high-redshift (z ~ 2 – 5)

molecular emission from young galaxies.

• With more frequencies opening up, the interest in observing in these new bands will increase.– Most significant new capability in 2009 will be

availability of Ka-band (26.5 – 40 GHz)

10

New EVLA Science: C-Band and K-Band Results

• C-band:– Traditional band is 4.5-5 GHz– Transition band is 4.2-7.7 GHz– First EVLA-only science: OH

masers• AU Gem & NML Cyg:

Sjouwerman et al. ( 2007, ApJL 666, 101)

• ON1: Fish (2008, ApJL 669, 8)

• K-Band:– Traditional VLA K-band: 21.2 - 25.2

GHz– EVLA band: 18.0 - 26.5 GHz– First interferometric detection of SiS

(1-0) at 18.154 GHz• IRC+10216 (CW Leo) • Claussen & Wooten

W3OHOH

6.035 GHz

IRC+01216SiS (1-0)

18.154 GHz

11

Software for Science Support Systems

• Proposal submission tool (PST)– Used for all VLA and GBT proposals

• Observation preparation tool (OPT)– Replacement for VLA JObserve – Development well underway– Tested by NRAO staff

• Observation scheduling tool (OST) – Under development– Demonstrated to ALMA software group– Alpha release next summer

• Archive access tool (AAT) – Will likely be common with ALMA’s– Standardized binary data format with

ALMA– Developing standard for science data

model now

12

The EVLA’s WIDAR Correlator• Replace existing VLA correlator with new wideband correlator

– Designed and developed by Canadian partner (HIA)• All 16 racks (8 baseline racks, 8 station racks) are installed and

cabled, awaiting the boards.

• Custom chips (12,000) received in April 2008

• On-the-sky tests of prototype began in July 2008

• First fringes on August 7

•4-antenna (6 baseline) data in hand

• Full production of boards to start in early 2009 (CDR in December 2008)

13

1.024 GHz-wide WIDAR fringes

14

New Science in the WIDAR Era

• When 10-antenna prototype tests are completed, (mid-late 2009?) we plan to move quickly to replace the existing VLA correlator.

• This WIDAR setup should provide, for all EVLA antennas, two basic modes:

1. Two independent sub-bands of 128 MHz each, with full polarization, and 128 channels/correlation.

2. One sub-band, RR and LL polarizations, 128 MHz BW, 512 channels per correlation.

• For both modes, the bandwidth can be divided by powers of two while keeping number of channels fixed.

• We will remain in this state for some time to ensure reliability and stability.

• When stable and reliable, the VLA correlator will be decommissioned. (Not sooner than late 2009).

15

Early WIDAR Science

• Most early science experiments with this initial WIDAR configuration will likely:– Utilize high frequency bands (K, Ka, Q)– Not utilize high spatial resolution

• By doing this, we minimize data set size and computing processing impact, and maximize science opportunities.

• Only EVLA antennas can be used with WIDAR – the unconverted VLA antennas will be temporarily decommissioned.– In Sept 2009, only 4-5 VLA antennas left.

16

WIDAR Science, 2010 and Beyond

• All WIDAR hardware components will be here by late 2009.

• WIDAR observational capabilities will rapidly grow through 2010.– Growth path not determined – much will depend on early

science opportunities.– Most likely path is to maximize bandwidth quickly.

• More complicated and flexible modes to be added (much?) later.– Increased number of channels– Greatly increased frequency resolution– Flexible correlator resource allocation– Pulsar mode observing– Phased array mode observing

17

Major Milestones

• Test 4-station prototype correlator on the sky July – Oct. 2008– Four antenna test and verification system– Not available for science

• Testing of 10-station correlator: Oct ’08 – Sept. 09

• Full Correlator Installation Jan ’09 – Dec ’09

• VLA’s correlator turned off Sept. 2009 – New correlator capabilities will be much greater – About 4 VLA antennas will not be usable (temporarily)

• Resident Shared Risk Observing Begins ~December 2009• Last antenna retrofitted Sept. 2010• Last receiver installed Sept. 2012

18

Resident Shared Risk Observing (RSRO)

• We are planning a ‘Resident Shared Risk Observing Program’, to begin in late 2009: – Experienced observers favored– Resident in Socorro for at least 2 – 3 months– Early access to EVLA data products– Proposals will be peer reviewed– Support is possible (but budgets are questionable)

• Details of this program under development• Announcement early next year (?)

19

NRAO Opportunities

• We are beginning a series of workshops to develop users knowledge of and interest in the EVLA.

• The first of a series of EVLA workshops, with the theme ‘The EVLA Vision: Galaxies Through Cosmic Time’, is being held in Socorro, December 16 – 18.

• Positions available! – Jansky Postdocs, – Tenure-track scientist – Software Management (CASA). – Check the NRAO website.

20

In Conclusion

• After many years of hard work, new EVLA systems are coming on line at a rapid pace.

• The WIDAR correlator is being assembled now, and undergoing testing.

• Correlator capabilities well in excess of those currently available will come in late 2009.

• Rapid expansion in capabilities – particularly in sensitivity and spectral surveying – will come through 2010.

• More exotic and powerful capabilities will arrive over the next few years.

• The EVLA will be, through the next one or two decades, what the VLA has been over the past two decades.