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e-VLBI progress in the South

This presentation discusses the progress and developments in e-VLBI (electronic Very Long Baseline Interferometry) technology, including the transition from tape to disk systems, digital filters, software correlators, network developments, and real-time fringe testing. It also highlights the current LBA (Long Baseline Array) system, telescopes in the Asia Pacific region, and plans for the future.

danielburrell
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e-VLBI progress in the South

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  1. e-VLBI progress in the South “Towards e-VLBI”  “e-VLBI” Tasso Tzioumis ATNF, CSIRO September 2006

  2. Outline • Overview - details in other presentations/posters • Current LBA systems/developments • Tapes - phasing out • DAS - digital filters • Disks - LBADR • Software Correlators • Network developments • “Real” e-VLBI tests • Plans & the Future

  3. LBA x NTD x New Norcia

  4. Long baseline Array (LBA) • Telescopes in Australia • ATNF, U.Tasmania, NASA - “core” Oz VLBI network • + South Africa • + Telescopes in Asia Pacific region • Japan, China, Hawaii, VLBA,… • Asia Pacific Telescope (APT)(VSOP support) • Open network (EVN model of operations) • http://www.atnf.csiro.au/vlbi • (+ Tests with NZ - fringes ok - no large antenna)

  5. LBA -S2 tape system • Canadian S2 VCR-based recorder • 8 VCR recorders  128 Mbps max data rates • S2 maintenance issues (no external support) • 7-station S2 LBA correlator at ATNF Sydney • XF architecture (ATCA correlator design) • Difficult to upgrade correlator • The main production-VLBI system for > 12 years • 2005 workshop: Phase-out S2 within ~3-4 years? • 2006 workshop: Decommission S2 in 2006-7!! • Move to disk-systems + software correlation • Correlation contracted to Swinburne - 1 October 2006

  6. LBA - DAS • DAS: Based on Digital Filters (> 10 years old!) • 2 input IFs @ 64 MHz BW (2 pols or 2 frequencies) • Sampling (10 bits) + Digital filters (ideal passbands) • Bands: 64MHz  125 KHz • S2 mode: 2 x 16 MHz ( 128 Mbps to match S2) • Huygens mode: 4 x 16 MHz (256 Mbps) • Maximum: 2 x 64 MHz (512 Mbps) - tested in 2006 • Multibit mode: 2 x 16 MHz x 8(10) bits  1 Gbps • Interference excision? • ATNF stations: 2 DAS units • 512 Mbps for Huygens (8 x 16 MHz) • 1 Gbps by 4 x 64 MHz channels - developed & tested in 2006 • Remains the main DAS for LBA system(s) • BUT no more units available!! • Move to new VLBI dBBC units? (Haystack) - timescales?

  7. LBADR - Disk recorders • (See C. Phillips poster for details) • PCEVN-Metsahovi VSI interface system • VSIC (ECL-LVDS) & VSIB(computer) • Connects to LBA DAS • All LBA antennas equipped • COTS computers • New Tyan “Thunder K8WE” motherboards (2005) • Multiple PCI bus systems • Internal disks; IDE removable disks; X-RAID on fibre channel • (Replaced test systems on Dell 1600SC servers) • Apple Xserve hardware RAID systems (7 TB)

  8. Software correlators • See poster by S. Tingay & A. Deller • FX software correlator(s) • Swinburne Supercomputer • 300 Dell computers in cluster • Real time correlation (“normal” modes) - 30-50 nodes • Smaller clusters at telescopes • (Parkes: 32 nodes; ATCA: 16 nodes) • Cray XD-1 supercomputer in WA + FPGAs • Under development • Very versatile & robust (can run on most systems) • Only correlators in Australia for disk systems!

  9. “Real-time” fringe testing • Disk-systems • Can run parallel to S2 VCRs (S2 C2 output port) • Short segment (~0.1s) data or use full recorded data • Transfer to Swinburne - (slow) ftp or fast links • Correlate and post on web • Start correlating immediately (not all data needed) • Fringe in a few secs; web post within minutes • Semi-automatic operation • Routine for all LBA observations • Setup fringe tests for all observations • http://pentane.ssi.swin.edu.au/~cphillip/ Increased LBA reliability and robustness

  10. Network connectivity -1 • See talk by Shaun Amy • AARNet3 Regional Network • Fibre tails to ATNF antennas in 2005-6 • $2M project, funded by CSIRO corporate • Fibre “tails” owned by CSIRO • “e-vlbi” tests in March 2006 - Official start June 2006! • Legal contract problems!! • 2 x 1 Gbps connectivity • 1 operating now; 2nd circuit to be connected • 10 Gbps (x multiple wavelengths) backbone • Good international connectivity

  11. AARNet3 Regional Network

  12. Network connectivity -2 • Swinburne: 1 Gbps link(s) constructed • Operation delayed by legal problems!! (again) • (10 Gbps link from Parkes?) • Enables software correlator connectivity • Hobart: Fibre links funded and in construction (2006) • 1 Gbps - telescope ---> University • 10 Gbps to AARNet • (BUT Bass-link limited to ~0.5 Gbps?) • WA Connectivity (Cray @ UWA) • CeNTIE: 3 x 1 Gbps BUT closes in 2006! • AARNet3 links planned • Impact on x-NTD? • (Tidbinbilla - NASA: 2 Mbps commercial links • Future links? )

  13. First Oz real “e-VLBI” • Date: 24 August 2006 • Antenna: Parkes, Mopra, ATCA • Data rate: 128 Mbps (per station) • Bandwidth: 2x16 MHz (per station) • Processor: Dual AMD server (ie only 2 CPUs) • No disk buffering --> “e-VLBI” • Time: 10minutes + • 1-bas test Parkes-ATCA at 256 Mbps/station

  14. Plans - Near term • Transition production VLBI to disk systems + software correlation (2006-7) • Investigate remote-disk recording • Acquire ~$0.5M of disks • Extensive “real” e-VLBI tests • To Swinburne cluster correlator (in 2006) • To JIVE correlator under EXPReS (2006-7) • Data disk formatting issues (LBA - Mk5a) - VSI-E?? • Tests to Haystack/Japan/Global - VSI-E?? • DAS replacement?

  15. Special “e-VLBI” Instrument? • Parkes-Mopra- Narrabri • 1 Gbps links installed • 1 Gbps data from 2 x DAS systems • Software correlation (Parkes or ATCA cluster)  Real-time VLBI instrument at 1 Gbps • Cf PTI instrument (Parkes -Tid @ 10 MHz BW) • Very popular with non-VLBI specialists • Fast detection observations/surveys • May operate in parallel with disk recording • E.g. correlate 2nd 512 Mbps stream from ATNF antennas

  16. Plans - Longer term • CABB - Broadband upgrade of ATCA • 4 Gsamples x (8) bits  32 Gbps streams • 4 IFs per antenna; 8 antennas • Digital Polyphase filters -- > CABB Correlator • ATCA operation in 2007-8 • VLBI capability designed-in (2008?) • Need for VLBI operation: • n x 10 Gbps connections to ATCA (Narrabri) • Broadbanding of Rx systems (Mopra, Parkes) • Narrabri polyphase filters? • Broadband and Fast links from non-ATNF antennas  Multiple 10 Gbps inputs & e-VLBI

  17. Basic Configuration Simple Zoom Multiple Zoom (>2 possible) FIR FFT FIR FFT FringeRotators Correlators DMUX Filterbank Compound Zoom A Wideband Upgrade for the Australia Telescope Compact Array Luneburg Lens Phased Array Luneburg Lens Phased Array 6 * 22m antenna AT Compact Array FPGA hardware may be completely reprogrammed to produce many different filterbank configurations, as different observations may require. A 2GHz bandwidth polyphase digital filterbank with 4096 channels ... ... will fit into four XC2V6000 FPGAs Filterbank Architecture RF, IF and Baseband Signal Path

  18. Summary • S2 tape LBA system to be decommissioned 2006-7 • LBADR - disk recorder developed • Software correlation - “real time” speeds • Very versatile, robust and portable • LBA transition: disk recording + software correlation • Digital DAS - need to augment/replace • 1 Gbps links to ATNF antennas operating • Links to correlator and other telescopes in construction • First “real” e-VLBI tests successful • Plans for eVLBI instrument (Pks-Mop-Nar) • Future: 10 Gbps links + CABB correlator

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