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Current LBA Developments

Current LBA Developments. Chris Phillips CSIRO ATNF. 13/7/2005. Disk Based Recording. Thanks to initial work by Uni of Tasmania and Swinburn Uni, the LBA has disk based recorders at all Australian stations & NZ Based on Metsähovi “VSIB” digital input card “PCEVN”

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Current LBA Developments

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  1. Current LBA Developments Chris Phillips CSIRO ATNF 13/7/2005

  2. Disk Based Recording • Thanks to initial work by Uni of Tasmania and Swinburn Uni, the LBA has disk based recorders at all Australian stations & NZ • Based on Metsähovi “VSIB” digital input card • “PCEVN” • Have just ordered 10 systems for uniformity across LBA

  3. System Setup • LBA DAS for sampling and digital filtering • Produces up to two 16 MHz bands for 2 IFs • 256 Mbps data rate • Parkes, Mopra and ATCA have 2 DAS (512 Mbps) • MRO “VSIC” converts S2 input data into VSI-H format • MRO “VSIB” PCI card used for data input into standard PC • Data recorded onto disk using normal Linux filesystem

  4. Recorder PC setup • Dual processor (AMD64 )Tyan motherboard • Dual onboard gigabit Ethernet • Primary disk recording into Apple Xserve RAID • 14  400 GB disks in RAID5 configuration • 4  400 GB removable IDE (PATA) disks in software RAID configuration for compatibility • Running on Promise Ultra133 TX2 • Also 2  400 GB internal SATA disks • 4 onboard SATA-II connectors

  5. Recorder Costs • PC with 800 GB disk space • €2410 ($A3890) • VSIB+VSIC input cards • €1090 • Apple Xserve RAID with 5.6 TB disk space • €9900 ($A1600) • 4x400 GB IDE PATA disks • €1014 ($A1640)

  6. Why Not Mark5? • Mark 5a not compatible with LBA DAS • MRO systems engineered to work with S2 data format • MRO system better suited to software correlation • Data recorded using normal Linux filesystems • Cost is similar to Mark5 • Apple Xserve RAID is major component

  7. Huygens VLBI Experiment • Intended to be Mark5 • Not compatible with LBA (Parkes, ATCA, Mopra, Ceduna) • Installed second DAS for experiment • Produced special cable to record data from 2 DAS onto one disk recorder

  8. Real Time Fringe Testing • Suite of networked Perl scripts allow almost realtime interactive fringe testing • 0.5-1 seconds of data transferred to Swinburne to correlate in software • Limited by slow networks, • 512 kbps for ATCA, Parkes • 33kbps modem for Hobart! • Can get fringes within 30sec • Usually a couple of minutes • Routinely run for all LBA experiments

  9. Observations to Date • First full LBA test experiment in April04 • Including Hart, VLBA, Kashima (Mk5, K5) • Also Nov04, May05 • Tests to NZ • Huygens experiment and Huygens tests • High spectral resolution of OH masers • 4 MHz, 16000 channels

  10. Disk VLBI Availability • Disk based recording added as option for OCT05 observing session • Shared risk basis • Data recorded at rates up to 512 Mbps • Possibly up to 1 Gbps • Will be correlated using Swinburne software correlator • Suitable for sensitive observations, high spectral resolution, pulsar coherence dedispersion etc

  11. Future Developments • MRO systems are not compatible with ATNF S2 correlator • Delay tracking performed by S2 playbacks • All disk & eVLBI correlation using Swinburne software correlator • May be able to do disk  S2 copying • On-going project to record 2x64 MHz bands from DAS (512 Mbps) • Currently problem with clocking • 2x16 MHz 8bit (or 10bit)

  12. eVLBI • Recorders equipped with dual onboard gigabit Ethernet • Suitable for 512 Mbps transfer • Initially record and transmit, then remote recording • Will experiment with realtime software correlation • Initially single baseline • Possibly to Uni of Western Australia

  13. Long Term Plan • New correlator being developed for ATCA • Based on FPGA digital filterbanks • Plan to use as VLBI correlator • Should handle data rates up to 64 Gbps • 2 GHz, 2 Pol, 8 bit

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