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Demonstration of 16Gbps/station broadband-RF VLBI system

Demonstration of 16Gbps/station broadband-RF VLBI system Alan Whitney for the VLBI2010 development team MIT Haystack Observatory 22 October 2012 1 st Intl VLBI Technology Workshop MIT Haystack Observatory. VLBI data-rate drivers. Geodetic VLBI (VLBI2010 project)

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Demonstration of 16Gbps/station broadband-RF VLBI system

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  1. Demonstration of 16Gbps/station broadband-RF VLBI system Alan Whitneyfor the VLBI2010 development team MIT Haystack Observatory 22 October 20121st Intl VLBI Technology Workshop MIT Haystack Observatory

  2. VLBI data-rate drivers • Geodetic VLBI (VLBI2010 project) • Near term: 16Gbps burst capture; 4Gbps sustained • Can use of weaker sources/shorter integration times • Long term: ~32Gbps burst capture; ~8Gbps sustained • mm-VLBI • Near term: Can use 16Gbps as soon as available • Coherence time typically <30 sec • Long term: Phased-ALMA will support 64Gbps

  3. Goal of Demonstration experiment • Assemble and demonstrate a complete dual-polarization VLBI broadband system capable of receiving and recording 4GHz of RF bandwidth • Process recorded VLBI data through DiFX software correlator to produce fringes • Analyze details to determine proper system functioning

  4. 16 Gbps VLBI demonstration with Mark 6 May/June 2012 2-14 GHz dual-pol

  5. System Block Diagram

  6. Front-end performance (Westford)

  7. RDBE-S Block Diagram 4 Gbps 4 Gbps 7

  8. Mark 6 prototype system • Fully COTS hardware except for chassis and disk modules • Disk modules are variant of Mark 5-SATA modules • Fully open-source software • Prototype system used RAID0 disk management • Slow-disk tolerant file system under development

  9. Prototype Mark 6 Recorder recording to 4 Mark 6 modules (32 disks) 9

  10. DiFX correlation, postprocessing • DiFX modified to support 1024 Msps sample rate/channel • HH and VV correlations done for all four frequency bands • DiFX output converted to ‘Mark 4’ format and imported into HOPS • Fringe-processing through updated fourfit fringe-finding software • No phase-cal: For weak source, channel-to-channel phase adjustments done by observing nearby stronger source

  11. 0550+356 GGAO-Westford 16Gbps17 May 2012 Delay rate (nsec/sec) 60 0 Time (sec) 13

  12. 3C84 GGAO-Westford 16Gbps19 June 2012 Delay rate (nsec/sec) 0 10 Time (sec) 14

  13. Summary • Full 2x2GHz (dual-pol) RF bandwidth processed and recorded • Successful processing on DiFX software correlator • First demonstration of 16Gbps of type to be used for geodetic-VLBI and mm-VLBI systems • Fundamentals of 16Gbps VLBI demonstrated; more work to do before fully calibrated and operational system 15

  14. Questions?

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