The Future of the VLBA 27 & 28 January 2011 Arecibo, the VLBA and the HSA Chris Salter Arecibo Observatory (National Astronomy & Ionosphere Center)

The Future of the VLBA27 & 28 January 2011

Arecibo, the VLBA and the Arecibo, the VLBA and the HSA HSA

Chris Salter Chris Salter

Arecibo Observatory (National Astronomy & Ionosphere Center)


Arecibo and VLBIArecibo and VLBI

• HSA, EVN (assoc. member) and Global Array operations.

• EVN eVLBI science runs at 256 & 512 Mbit/sec.

• Acquisition, construction and commissioning of a 12-m VLBI phase-reference dish.

• Acquisition of 2 × Mark-5C recorders, and the imminent delivery of 2 × digital back-ends (RDBEs).

The High Sensitivity Array (HSA)The High Sensitivity Array (HSA)

The EVNThe EVN


Arecibo VLBI Sensitivity UpgradeArecibo VLBI Sensitivity UpgradeIncreasing the US VLBI data recording rate to at least 4 Gbps by 2010 was a

goal set by the Taylor Committee (2004).

Arecibo is in the process of:

1. Increasing the Recorded Bandwidth: (a) Replacing our analog DAR with a Digital Back End (RDBE). Arecibo has ordered

two RDEs from NRAO, and delivery is expected early in 2011.

(b) Upgrading to Mark5C recording. Arecibo has purchased and received two Mark5C units from Conduant Corp. Control software is under development at Haystack and will be installed there in our units.

2. Increasing Integration Time: The low slew rate of the 305-m dish can lead to > 50% loss of integration time

in phase-referenced VLBI. The new Arecibo 12-m dish will track the phase-calibrator continually, while the 305-m tracks the target, just occasionally visiting the calibrator. Phases derived from the 12-m data will be applied to the 305-m data under the assumption that the same ionospheric corrections apply to both data sets.


The Arecibo 12-m AntennaThe Arecibo 12-m Antenna

12-m Antenna Site

The Arecibo 12-m Patriot Antenna

Access Road (then nearing completion)

The antenna is currently undergoing acceptance tests. Observations will begin with a coaxial S/X feed, with a wideband receiver. Will be able to cover +90° < δ < –66°.


The Arecibo 12-m Antenna The Arecibo 12-m Antenna

Why 12-m?: A 12-m antenna provides a baseline sensitivity within a factor of 2 of a VLBA dish. Sources brighter than ~110 mJy can be used for phase referencing.

Frequency Coverage: L, S, C & X bands are required for use with the 305-m dish; S/X bands are being installed initially. Thereafter, a 1 – 12 GHz broad-band front-end is anticipated.

Other Potential Uses: (a) Possible participation in regular VLBA operations, (b) Geodesy within the umbrella of VLBI2010; (c) The L-band, voltage beamwidth of the 12-m antenna contains all 7 ALFA beams, opening up the possibility of multi-beam interferometric applications, (d) Education and research applications with Puerto-Rican universities and other educational establishments.


Postscript re-the 305-m Postscript re-the 305-m DishDish• The Arecibo 305-m telescope suffered a serious structural

failure to a girder in the suspended platform in early 2010.• Emergency repairs allowed operations over 3.5° < Zenith

Angle < 12° from March 2010.• The permanent repair was undertaken in two phases. The

first phase was completed in Oct. 2010 and allowed operations over 1.1° < Zenith Angle < 16°.

• The second phase nears completion, and full motion of 1.1° < Zenith Angle < 19.7 deg will be restored early in Feb. 2011.


Muchas Muchas GraciasGracias

PY 2010 NAIC Progress Report & Program Plan Review2nd December 2010

e-VLBI: Monitoring the M87 Jet during a TeV Outburst

Optical HST image of M87 Jet and a knot of hot gas, HST-1, seen to be brightening in 2005, with subsequent TeV outbursts.

Superluminal motion (V

app~2.7c) in HST-1

during a TeV outburst

The inner Jet (collimated for ~200 mas) and the weaker complex, HST-1 (at 800 mas from the core), imaged at 5-GHz, with resolution 7 x 3 mas, and map noise of 0.12 mJy/beam.

Nov19

Jan27

Feb10

Nov19Nov19

Mar02

Mar30


2. Increasing the Integration Time

VLBI is severely limited by ionospheric and tropospheric phase fluctuations, leading to a loss of coherence. As a solution, many VLBI observations these days are taken in “Phase referenced” mode. The most commonly used form of this mode needs slewing between the target and a strong, compact calibration source (generally within a few degrees of the target) every 3-4 min. Phase, derived from the calibrator, is then applied to the target data.

The low slew rate of 305-m antenna can lead to over 50% loss of integration time in phase-referenced VLBI.


ReceiversReceivers

800


Existing Arecibo VLBI CapabilityExisting Arecibo VLBI Capability

DAR - VLBA4

MK5A

Max 1-GHz IF

The Big Dish(Gain~10k/Jy,SEFD~3-5 Jy)

Correlator

Internet

FedEx

1024 Mbps256 MHz (max)2 x 8, 16 MHz.05, .5 (#1,2 Rxs), 1 GHz

327, 800, L, S-Lo, S-High, C, C-High, X

Total data rateTotal single-pol RF Bandwidth

# of BBCs & Max ∆ν/BBC

Max. IF bandwidth/Rx

Receivers

Co-Observing Networks:

1.VLBA + Ar & the HSA (HSA, includes the phased-VLA,

GBT, EF)2. European VLBI Network + Ar 3. Global - Network4. eVLBI (Real-time VLBI via

internet: as yet with the EVN only)


Anticipated Developments over PY 2011Anticipated Developments over PY 2011

• Continued development towards a 40-beam focal-plane phased feed array to give an HI mapping array with the observing speed of ASKAP or MeerKAT.

• Developments towards replacing the present four receivers covering 2 to 8 GHz with two broader-band systems.

• Developments towards bringing the RF signals directly to the Control Room.

• Completion of VLBI equipment upgrade to a digital backend and Mk5C recorders allowing regular recording at up to 4 Gbits/sec.

• Implementation of the VLBI “phase transfer” methodology from the 12-m calibration data to the 305-m target data.


• A continuum observation, =18-cm, data-rate=512 Mbps, i.e. 128 MHz of RF bandwidth, dual-polarization, = 120 minutes on source:

Arecibo’s Contribution to the ArraysArecibo’s Contribution to the Arrays

• A spectral-line observation, =18-cm, 64 channels over 1-MHz, 2 pol, 120 min.

0.25 mJy/beam/ch 0.62 3.00.310.9 mJy/beam/ch

VLBA+Y27+Gb+ARVLBA+Y27+GBVLBAEVN+AREVN

HSA (VLBA+Y27+EF+GB+Ar) -Ar

1σ Image noise = 3.3 μJy/beam 7.1 μJy/beam

EVN+Ar-Ar

1σ Image noise = 3.8 μJy/beam 9 μJy/beam

Global (EVN+VLBA+Y27+Gb)+Ar-Ar

1σ Image noise = 2.5 μJy/beam 4.7 μJy/beam


Operational block diagram (evolving)

Documents

The Future of the VLBA 27 & 28 January 2011 Arecibo, the VLBA and the HSA Chris Salter Arecibo Observatory (National Astronomy & Ionosphere Center)