e-EVN and VSOP-2

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e-EVN and VSOP-2

• Zsolt Paragi (JIVE),
• for the EXPReS project

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Relevance The EVN will be a key partner to
VSOP-2. Current developments will have a direct
impact on VSOP-2 operations. Talk This talk
will focus on data transfer and network
reliability related issues. The EXPReS e-VLBI
project will be introduced. Challenges,
solutions, and the most recent results will be
shown. Will close with a few thoughts about the
(e-)EVN and VSOP-2.
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What is EXPReS?

• EXPReS Express Production Real-time e-VLBI
  Service
• Three year project, started March 2006, funded by
  the European Commission (DG-INFSO), Sixth
  Framework Programme, Contract 026642
• Objective to create a distributed, large-scale
  astronomical instrument of continental and
  inter-continental dimensions
• Means high-speed communication networks
  operating in real-time and connecting some of the
  largest and most sensitive radio telescopes on
  the planet
• Initiated and formerly coordinated by Mike
  Garrett, now coordinated by Huib J. van
  Langevelde
• http//www.expres-eu.org/

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e-VLBI for science

• Regular e-VLBI test observations in every six
  week (on average)
• 24h time is pre-allocated for science
  observation during each
• e-VLBI test
• Observing proposals submitted up to normal
  deadlines
• - short projects, preparing for
  normal EVN runs
• - spectral line experiments
• - continuum, including ToO and
  triggered projects
• May trigger proposals 24h hours before
  observations
• Science operations so far at 1.6 and 5GHz at
  32-512 Mbps
• (Cm, Jb2, Mc, On, Tr, Wb)
• More info at http//www.evlbi.org/evlbi/evlbi.html

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Science projects in 2006/2007

• Cyg X-3, 20 Apr/18 May, 128 Mbps, Tudose et al.
• GRS1915105, 20 Apr, 128 Mbps, Rushton et al.
• LSI 61.303, 256 Mbps, 26 Oct, Perez-Torres et
  al.
• Algol, 26 Oct/14 Dec, 256 Mbps, Paragi et al.
• Calibrators near M81, 14 Dec, 256 Mbps,
  Brunthaler et al.
• INTEGRAL microquasar candidates, 14 Dec, Pandey
  et al.
• double header run, 15 XRBs, 29 Jan, Rushton
  Spencer
• Calibrators, 21 Feb, 256 Mbps, Tudose et al.
• J20203631 microquasar candidate, 28 Mar, 256
  Mbps, Martí et al.
• Cyg X-3, 12-13(?) Jun, 256 Mbps, Tudose et al.
• Stellar maser search, 22-23 Aug, 32 Mbps,
  Langevelde et al.
• INTEGRAL source redo, 6-7 Sep, 256 Mbps, Pandey
  et al.
• Type Ib/c SN 2007gr, 6-7 Sep, 256 Mbps, Paragi
  et al.

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EXPReS challenges and solutions

• TCP protocol operating on normal network limited
  operations
• to 256 Mbps even within Europe
• - lightpathes to telescopes (dynamically
  allocated in the future?)
• - UDP-based protocol developed
• Mark5A software was not stable enough, modified
  software
• Station Unit crashes rewrote software, SU reboot
  during correlation job is now possible Mark5B
  will retire SUs
• Station Mark5As may be rebooted from JIVE without
  stopping
• the correlation job
• Longest uninterrupted e-VLBI job is 12h 43m!
• 1024 Mbps formatted data over 1 Gbps equipment
  does not work drop few percent of the packages
  (but keep headers)
• Connection very limited to some telescopes drop
  subbands (being tested at the moment)

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Test results
Happy JIVE staff in Dwingeloo
APAN live demo in China (August 2007) fringes
between EU telescopes and Shanghai and Mopra.
Demonstrated feasibility of global e-VLBI
observations with an ad-hoc array. Note
Australian data format was converted in real-time.
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Science results from the Oz-demo
ATCA, Mopra and Parkes observations at 512 Mbps,
correlated at JIVE. Target the nearby supernova
in the LMC, only visible from the South.
One of the breathtaking Hubble Space
Telescope images of SN1987A
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And with VLBI
Various fits to the data to measure the size of
the expanding remnant. Tingay et al., (in prep.)
Highest resolution image of SN1987A so far (first
VLBI!) not bad for a three telescope array.
Countours shows an earlier ATCA image.
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Tests in 2008, happy new year for EXPReS
First 1 Gbps e-EVN image with packed dropping.
Cm, Jb, Mc, Tr, Wb participated. Not all had
fringes in all subbands, but from the data
transfer point of view it was a 1 Gbps result.
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New e-telescopes every week!

• Effelsberg joins the e-EVN on
• 1st of April 2008, in all subbands
• up to 1 Gbps data rates.
• Most recently Hartebeesthoek live demo fringes at
  32 Mbps
• and Arecibo-TIGO (6m dish in Chile) fringes at
  64 Mbps

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Gentlemen pleased in South Africa
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and in JIVE

• This was a few minutes with fringes between
  Arecibo and Hart

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Science highlight from 2007
Supernova 2007gr detected on 6 Sep. Just 400
uJy! 256 Mbps, no Ef. First ATel message from
the e-EVN. Followed-up with a global VLBI
array. Paragi et al. (2007)
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Science in 2008

• Arp299 SNe by Perez-Torres et al. in April very
  robust operations
• (longest correlation job at JIVE see MERLIN
  image of target and
• e-VLBI throughput graph to the right )
• Followed by the first ever triggered e-EVN
  triggered project Cyg X-3 accretion disk state
  change (Tudose et al.)
• ATel publication.
• In May Cyg X-3 flared, three epochs e-EVN
  ToO the first ToO observations on unscheduled
  date. All of these at 512 Mbps. First pipeline
  image from 4h of data produced during the
  experiment.

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JIVE software correlator

• JIVE software correlator replaced NICT (CRL)
  software for ftp
• fringe tests.
• Doing RD on GRID-based software correlation.

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e-EVN and VSOP-2 data transfer

• The e-EVN will aim for 10 Gbps operations, which
  is feasible
• already now from networking point of view.
  VSOP-2 will be limited to 1 Gbps.
• The EVN will not abandon disk recording
  completely, which ensures operations with VSOP-2
  (needs accurate orbit for correlation, thus
  cannot be real-time) but data may be put to the
  network immediately instead of local storage at
  the telescopes.
• Central data storage and distributed software
  correlation on the GRID is a possibility. Data
  acquisition system difference is not a problem,
  but software must be there to translate data on
  the fly.

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e-EVN and VSOP-2 operations

• Although real-time space VLBI is not possible,
  must establish a quick fringe checking mechanism
  like the ftp tests in the EVN. This will allow
  monitoring of the array performance.
• Automatic data pipeline and easy access through
  data archive like in the EVN would help space
  VLBI users.
• e-EVN quick fringe-test results prior to VSOP-2
  survey (or ToO) observations may be desirable
  note that because the candidate sources are very
  variable at these frequencies a pre-launch survey
  may not be useful at all. Even total flux density
  measurements prior to VSOP-2 observations will
  not guarantee source compactness (although likely
  will be sufficient most of the time).