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NEW USE of An old correlatoR

NEW USE of An old correlatoR. Arpad Szomoru Joint Institute for VLBI in Europe. Mark IV EVN Correlator. Developed by international consortium: EVN institutes, MIT Officially inaugurated October 1998 Comparable correlators in use at Haystack Obs., US Naval Obs., MPIfR, JIVE

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NEW USE of An old correlatoR

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  1. NEW USE of An old correlatoR Arpad Szomoru Joint Institute for VLBI in Europe

  2. Mark IV EVN Correlator • Developed by international consortium: EVN institutes, MIT • Officially inaugurated October 1998 • Comparable correlators in use at Haystack Obs., US Naval Obs., MPIfR, JIVE • Correlator boards in use at WSRT, SMA

  3. Basic specifications • Input: • No. of telescopes (N) 16 • Array Observing frequencies: 329 MHz – 22 GHz • Data bandwidth: 128 MHz per polarization (Right and Left-hand circular), divided into 8 bands. • Channel bandwidths 0.5 MHz to 16 MHz. • Data input rate: 1 Gbps per telescope • Output: • Integration time 1/4s (will become 1/32s with PCInt) • 2048 spectral channels per baseline/band/polarization • Data Output rate 6 MB/s (will become 80 MB/s with PCInt)

  4.  VLBI FoV x 100 6 arcmin [FWHP] Effelsberg beam Field of View limitation • Limited by tint • Time smearing • Shorter integrations • Enable wide field surveys • Study μJy sources • Discriminate AGNs • But, enormous increase of output data volume..

  5. EVN MkIV Correlator limits • Integration time • Cycle time of 0.015s (actually, 1/64th of a second) • Spectral resolution • 131072 complex lags per readout = 65536 spectral points per readout • Divided over 32 products leads to 2048 spectral channels per product PCINT : • Short for Post Correlator Integrator • Capture the full output of the EVN MkIV correlator to disk • Need to replace output datapath

  6. The PCInt project • High speed readout of the correlator was already prepared • Via DSP powered serial port • Need hardware and software to enable this • Receiving end of serial port • Gbit ethernet for transfer from correlator rack to data collection host • Fast disk subsystem in order to support 160MByte/s (parallel RAID arrays in a Storage Area Network) Harro Verkouter

  7. RT System Correlator Board (x8) VME High Speed Serial C40 COMM PCI Ethernet Card 100TX 1000FX (x8) SBC (x2) Correlator rack (x4) Switch CCC DDD (xn) Fibre Channel EEE (xk) FC Switch Raid Array (xm) Current situation

  8. RT System Phase 0 Correlator Board (x8) High Speed Serial VME C40 COMM PCI Ethernet Card 100TX 1000FX (x8) SBC (x2) Correlator rack (x4) Switch CCC DDD (xn) Fibre Channel EEE (xk) FC Switch Raid Array (xm)

  9. RT System Phase 1 Correlator Board (x8) High Speed Serial VME C40 COMM PCI Ethernet Card 100TX 1000FX (x8) SBC (x2) Correlator rack (x4) Switch CCC DDD (xn) Fibre Channel EEE (xk) FC Switch Raid Array (xm)

  10. RT System Phase 2 Correlator Board (x8) High Speed Serial VME C40 COMM PCI Ethernet Card 100TX 1000FX (x8) SBC (x2) Correlator rack (x4) Switch CCC DDD (xn) 1000TX EEE (xk) Raid Array (xn)

  11. Post-processing issues • Huge data volumes1hour @160MByte/s equals560GBytes of data • Use a cluster of nodes • Need automated processing • Use a processing pipeline Achieved 1/16s sampling, at 24 MB/s data output Users seem to be ready for 800 GB data-sets…

  12. Price recording media ($/GB)

  13. Data Acquisition Disk based recording • Move from tape to disk recording • Reliability • Cost • Bandwidth • Efficiency • e-VLBI: the next step • No consumables • Higher bandwidth • Fast turn-around • ToO support e-VLBI using fiber

  14. Why e-VLBI ? • Reliability – real-time feedback to the telescopes • Logistics – No media management • Sensitivity – sustained data rates >> 1 Gbps possible… • Rapid science results: • Geodesy (Earth rotation rate) • Precision spacecraft navigation • Transient phenomena… GRBs, SNe etc.

  15. Why e-VLBI (cont) ? • Target of Opportunity (ToO) capability: • Dominated by VLBA currently… • Reliability & Logistics  e-VLBI • Sensitivity  e-VLBI • Rapid science  e-VLBI • Rapid publication  e-VLBI • Optimal observing strategy (obs. freq., calibrators, telescope array) • LOFAR Transients etc.  ToOs may become much more common  e-VLBI.

  16. e-VLBI Proof-of-Concept Project • DANTE/GÉANT Pan-European Network • SURFnet Dutch NREN • GARR Italian NREN • UKERNA UK NREN • PSNC Polish NREN • DFN German NREN • KTHNOC/NORDUnet Nordic NREN • Manchester University Network application software • JIVE EVN Correlator • Westerbork telescope Netherlands • Onsala Space Observatory Sweden • MRO Finland • MPIfR Germany • Jodrell Bank UK • TCfA Poland • CNR IRA Italy

  17. GÉANT: Access of NRENs to GÉANT 0 HU CH IT SE FR DE GR NL CZ BE GEANT AT 2.5 G 1.2 G GEANT UK PT 622M ES 310 M SI PL IE 155 M 34 M 45 M HR LU EE RO EVN telescope SK LV BG IL CY LT

  18. POC results • Demonstration of feasibility • Identification of problems • Has led to closer ties with networking community and generated political interest • Has laid the foundation for the next step forward (EXPReS): • I3 proposal to the EC (Communication & Network Development Call) • Ranked first out of 43 proposals; nearly fully funded to an amount of 3.9 MEuro.

  19. EXPReS – major aims: • Making e-VLBI an operational astronomical instrument: • 16 telescopes connected to JIVE at 1 Gbps • Robust real-time e-VLBI operations • Transparent inclusion of e-MERLIN antennas within e-EVN • Target of Opportunity Capability • Future developments in e-VLBI • >> 1 Gbps data transfer rates, • extended LOFAR etc. • distributed software correlation.

  20. Expanding the e-VLBI Network

  21. Network testing • Use existing protocols on currently available hardware • TCP maximal reliability • Not really required • Sensitive to congestion • Lot of fine-tuning necessary • And possible • UDP connectionless • Unaccountable • Tailor made protocols? • Lambda switching • Internet weather • Hard to quantify • Hard to pinpoint bottlenecks

  22. Network testing (2) • February 2005: network transfer test (BWCTL) employing various network monitoring tools involving Jb, Cm, On, Tr, Bologna and JIVE

  23. First real-time eVLBI Image, 3 telescope observation of gravitational lens, May 2004 First eVLBI science observation, OH masers around IRC10420, Richards et al, Oct 2004 First broadband eVLBI science, detection of the Hypernova SN2001em, Paragi et al, astro-ph/0505468

  24. First open e-EVN Call for Proposals (March 2006) • First Target of Opportunity Observations (May 2006, Cygnus X-3), Tudose et al. (in prep)…

  25. Current status • Regular science runs at 128 Mbps with 6 European stations (24 hours) • Arecibo sometimes participates at 32 Mbps • Fringes from all European stations at 256 Mbps have been demonstrated, and, • on single baselines, 512 Mbps

  26. Issues, Developments Convincing a correlator designed for tape technology to become real-time.. Operational improvements: • Robustness • Reliability • Speed • Ease • Bandwidth • Station feedback

  27. Ongoing New control computers (Solaris AMD servers) • Cut down on (re-)start time • Powerful code development platform • Tightening up of existing code Other hardware upgrades: • Upgrade existing connectivity from 6*1 Gbps to 16*1 Gbps (lightpaths) • SX optics (fibres + NICs) • Replacement of SU functionality: Mark5A→B: motherboards, memory, power supplies, serial links.

  28. Conclusions • e-VLBI is changing the nature of VLBI • Fast response, ToO capability • better quality control, rapid data delivery • New science, higher bandwidths • Large fields of view • Will allow the study of μJy sources • Or many masers over a large star formation region • Data archive will contain millions of weak sources • EXPReS will realize an operational e-VLBI network distributed across 1000’s km – a true pathfinder for SKA.

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