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)
The Future of the VLBA27 & 28 January 2011
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
The Future of the VLBA27 & 28 January 2011
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 Future of the VLBA27 & 28 January 2011
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 Future of the VLBA27 & 28 January 2011
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.
The Future of the VLBA27 & 28 January 2011
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.
The Future of the VLBA27 & 28 January 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
The Future of the VLBA27 & 28 January 2011
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.
The Future of the VLBA27 & 28 January 2011
ReceiversReceivers
800
The Future of the VLBA27 & 28 January 2011
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)
The Future of the VLBA27 & 28 January 2011
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.
The Future of the VLBA27 & 28 January 2011
• 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
The Future of the VLBA27 & 28 January 2011
Operational block diagram (evolving)