e-VLBI – Creating a Global Radio-Telescope Array via High-Speed Networks

1. e-VLBI – Creating a Global Radio-Telescope Array via High-Speed Networks Alan R. Whitney MIT Haystack Observatory Internet2 Fall Member Meeting San Diego, CA 11 Oct 2007

2. Traditional VLBI The Very-Long Baseline Interferometry (VLBI) Technique(with traditional data recording) The Global VLBI Array(up to ~20 stations can be used simultaneously)

3. VLBI Science • ASTRONOMY • Highest resolution technique available to astronomers – tens of microarcseconds • Allows detailed studies of the most distant objects – quasars, gravitational lenses, GRBs; as well as black hole at center of Milky Way Plate-tectonic motions from VLBI measurements • PRECISION GEODESY • Highest precision (few mm) technique available for global tectonic measurements • Highest spatial and time resolution of Earth’s motion in space for the study of Earth’s interior • Earth-rotation measurements important for military/civilian navigation • Fundamental calibration for GPS constellation within Celestial Ref Frame VLBI astronomy example

4. VLBI Data Rates and Volume • Astronomy experiments at 1-4 Gbps/station, 4 to 20 stations • ~5-40 TB/station/day • Global 10-station experiment @ 4 Gbps/station  up to ~400 TB/day • Single 10-day experiment can produce up to ~4 PB • Higher data rates (8-32 Gbps) are already on the horizon • Available disk supply can support only few days of observations at these rates • All pairwise telescope combinations must be cross-correlated Uniqueness of VLBI data • Transmitted data are uncompressible white Gaussian noise; useful signals appear only after correlation processing • Loss of some data is tolerable “e-VLBI” is a natural fit to high-speed global networks!

5. Why do e-VLBI? • Pre-experiment verification and diagnosis • Rapid processing turnaround • Astronomy • Quick feedback for adjustment of observations • Geodesy • More timely Earth-orientation measurements; important for precision military and civilian navigation • Bandwidth growth potential for higher sensitivity • VLBI sensitivity is proportional to SQRT(bandwidth),limited by availability of media • e-VLBI potential bandwidth to 100 Gbps/station or more • Elimination and/or reduction of expensive media pool

6. The Colloquial Competition – a B747 loaded with 1 TB disks! Payload: 140 tons ≈ 140,000 disks = 140 PBBased on 24-hr flight time, bandwidth is ~10 Tb/sec!Cost estimated at $250,000 per flight! Note: In 1970, with 12” open-reel computer tape at 800 bpi, B747 bandwidth was only ~100 Mbps – down a factor of 100,000 from today!

7. Clearly, e-VLBI is possible and attractive, but there are a few problems…… • Not all antennas are connected; many are in remote locations – high capital cost • If even a single antenna cannot deliver data to correlator, all data must be recorded • Shared networks are unable to deliver deterministic and repeatable performance to demanding applications (such as e-VLBI) • Unpredictable conditions within the network itself • TCP protocol congestion response can cause major data-rate slowdowns • UDP is not TCP friendly and is frowned upon in most shared networks

8. International e-VLBI Demonstrations • iGRID-05 Networking Conf. San Diego, CA Sep 05 • SC-05 Supercomputer Conf. Seattle, WA Nov 05 Internet2 Driving Exemplary Applications (IDEA) Award to “Very High Speed VLBI (e-VLBI)”. Alan Whitney (MIT/Haystack), Arpad Szomoru (JIVE), Y. Koyama (NICT), and Hisao Uose (NTT) Apr 26, 2006 – Arlington, VA

9. 1 Gbps 155 Mbps

10. e-VLBI Network in Japan KSP Kashima Station Usuda Deep Space Center (ISAS) Kashima Space Research Center (CRL) JGN2 Nobeyama Radio Observatory (NAOJ) GEMnet2/NTT PW/Internet2 NTT Musashino R&D Center SINET3 Gifu University GSI SINET3 KSP Koganei Station Yamaguchi University National Astronomical Observatory of Japan (NAOJ) National Institute of Information and Communication Technology (NiCT)

11. Connectivity in Australia – current and planned

12. VLBA – Very Long Baseline Array N. LibertyIA Mauna Kea HI BrewsterWA Owens ValleyCA HancockNH Kitt PeakAZ Pie TownNM St. CroixVirgin Is. Fort DavisTX Los AlamosNM

13. Collaborations • e-VLBI is a highly collaborative global program • Collaborations with: • NASA Goddard Space Flight Center • University of Maryland/ISI-E/GMU DRAGON project • Caltech High Energy Physicists under the leadership of Harvey Newman • Caltech Netlab Department • R&E Networks: Internet2, Dante, SURFnet, APAN, NORDUnet, SUNET, SINET • JIVE, The Netherlands • Jodrell Bank, England • Max Planck Institute, Germany • Shanghai Radio Observatory, China • CSIRO, Australia • NICT, Japan

14. e-VLBI Challenges • Connect the telescopes to high-speed networks • Proceeding well in Europe, Japan, Asia and Australia • Many U.S. telescope are very isolated; very expensive to connect • Find schedulable, reliable global high-speed connections • On-demand dynamic circuit networks are ideal, and probably required at higher data rates • HOPI and DRAGON hybrid networks have been first step • Challenge to set up across multiple international domains • Need quick identification and resolution of failure points across multiple international domains • Distributed cross-correlation processing must be developed to eliminate extreme data-rate concentration at correlator; some work is in progress • Cost of doing e-VLBI must be competitive recording/shipping

15. So ……. The Bottom Line! • e-VLBI has tremendous potential to improve both the science output and the rate of science output from global VLBI observations • e-VLBI is probably the only practical way to extend data rates significantly beyond 10 Gbps/station • Progress is being made, but significant investment must be made to fully realize potential • The objectives of global CyberInfrastructure initiatives to provide on-demand, high-bandwidth, dedicated circuits across multiple global domains are key to long-term success. Thank you!