Post on 27-Mar-2015
e-EVN and VSOP-2
Zsolt Paragi (JIVE),for the EXPReS project
2008 May 14-16 VSOP-2 meeting, Bonn Slide #2
Relevance
The EVN will be a key partner to VSOP-2. Current developmentswill 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 closewith a few thoughts about the (e-)EVN and VSOP-2.
2008 May 14-16 VSOP-2 meeting, Bonn Slide #3
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/
2008 May 14-16 VSOP-2 meeting, Bonn Slide #4
2008 May 14-16 VSOP-2 meeting, Bonn Slide #5
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
2008 May 14-16 VSOP-2 meeting, Bonn Slide #6
Science projects in 2006/2007• Cyg X-3, 20 Apr/18 May, 128 Mbps, Tudose et al.
• GRS1915+105, 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.
• J2020+3631 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.
2008 May 14-16 VSOP-2 meeting, Bonn Slide #7
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)
2008 May 14-16 VSOP-2 meeting, Bonn Slide #8
Test results
APAN live demo in China (August 2007): fringes between EU telescopes and Shanghai and Mopra. Demonstrated feasibility ofglobal e-VLBI observations with an ad-hoc array. Note Australiandata format was converted in real-time.
Happy JIVE staff in Dwingeloo
2008 May 14-16 VSOP-2 meeting, Bonn Slide #9
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 breathtakingHubble Space Telescopeimages of SN1987A
2008 May 14-16 VSOP-2 meeting, Bonn Slide #10
And with VLBI…
Highest resolution image of SN1987Aso far (first VLBI!) – not bad for a three telescope array. Countours showsan earlier ATCA image.
Various fits to the data to measure the sizeof the expanding remnant.
Tingay et al., (in prep.)
2008 May 14-16 VSOP-2 meeting, Bonn Slide #11
Tests in 2008, happy new year for EXPReS
First 1 Gbps e-EVNimage with packed dropping.
Cm, Jb, Mc, Tr, Wb participated. Not allhad fringes in allsubbands, but from thedata transfer point of view it was a 1 Gbps result.
2008 May 14-16 VSOP-2 meeting, Bonn Slide #12
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
2008 May 14-16 VSOP-2 meeting, Bonn Slide #13
Gentlemen pleased in South Africa
2008 May 14-16 VSOP-2 meeting, Bonn Slide #14
…and in JIVE
This was a few minutes with fringes between Arecibo and Hart
2008 May 14-16 VSOP-2 meeting, Bonn Slide #15
Science highlight from 2007
Supernova 2007grdetected on 6 Sep.Just ~400 uJy!256 Mbps, no Ef.
First ATel messagefrom the e-EVN.
Followed-up with aglobal VLBI array.
Paragi et al. (2007)
2008 May 14-16 VSOP-2 meeting, Bonn Slide #16
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.
2008 May 14-16 VSOP-2 meeting, Bonn Slide #17
JIVE software correlator• JIVE software correlator replaced NICT (CRL) software for ftpfringe tests.
• Doing R&D on GRID-based software correlation.
2008 May 14-16 VSOP-2 meeting, Bonn Slide #18
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.
2008 May 14-16 VSOP-2 meeting, Bonn Slide #19
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).