1. Huib Jan van Langevelde Joint Institute for VLBI in Europe, Dwingeloo NL radio-astronomy a telescope larger than Europe radio-astronomy a telescope larger than Europe

2. huib 1/3/08 2/19Geant, Bled, Slovenia, March 4 2008 Outline Radio-astronomy About resolution and sensitivity Introducing Very Long Baseline Interferometry e-VLBI, how the Network becomes the telescope Hardware, infrastructure, protocols An operational e-VLBI network Science objectives Special requirements Guaranteed bandwidth, dedicated light-paths Intercontinental VLBI Beyond operational network Current R&D programme Directions in radio-astronomy Ambitions for future e-VLBI programmes

3. huib 1/3/08 3/19Geant, Bled, Slovenia, March 4 2008 Radio-astronomy Radio waves with λ of 0.7mm to 90cm Compared to optical light 400 – 700 nm Can be detected and amplified with antenna radio emission from hot gas between the stars Super bright emission from vicinity of black holes Active Galaxy at 1cm radio emission

4. Connected Radio- Interferometry like Westerbork with long baselines can observe interesting detail in radio sources Need even longer baseline to see astronomy in motion! Radio emission from astrophysical plasmas can be detected against sky noise with telescopes larger than few meters To reach interesting resolution need kilometer baselines Interferometer measures Fourier components of the sky brightness

5. huib 1/3/08 5/19Geant, Bled, Slovenia, March 4 2008

6. huib 1/3/08 6/19Geant, Bled, Slovenia, March 4 2008 VLBI digital processing To reach the faint end of the universe… Need many big telescopes And as much frequency space as you can get bandwidth!i.e. bandwidth! radio sources in the Hubble deep field require several days of integration (Garrett et al., 2000) Current standard is 1Gb/s Recording 256 MHz in 2 pols bits are not sacred, losses tolerable Recording on parallel hard disks

7. huib 1/3/08 7/19Geant, Bled, Slovenia, March 4 2008 Now turn to e-VLBI! Upgrade EVN to e-EVN Funding through EXPReS project in 2006 Retrofit correlator to work real-time Help solve last mile problem at telescopes Work closely with NRENs on robust connectivity And become operational at a competitive sensitivity Push to 1024 Mb/s limit Bring in the big telescopes And start the revolution in radio- astronomy culture

8. huib 1/3/08 8/19Geant, Bled, Slovenia, March 4 2008 Remarkable progress 6 telescopes regularly on line, interesting for science Correlator operations optimal for direct results and feedback Connectivity reached impressive reliability Started with TCP, but obviously not the optimal protocol for e-VLBI light-pathsNow dedicated light-paths to most telescopes UDP protocols implemented for optimal streaming Size of balloon set by number of telescopes participating, height by station sustained bit-rate

9. huib 1/3/08 9/19Geant, Bled, Slovenia, March 4 2008 Recent progress Managed to get almost full sensitivity at 1024 Mbps Selectively dropping data Got connectivity to big 100m telescope at Effelsberg (D) In collaboration with LOFAR Major issue for astronomical competitiveness First science runs in April

10. huib 1/3/08 10/19Geant, Bled, Slovenia, March 4 2008 Made lots of progress

12. huib 1/3/08 12/19Geant, Bled, Slovenia, March 4 2008 Why e-VLBI is exciting for science? Rapid response for rapid variability Fast response to requests Immediate analysis of data, adapt observing parameters Coordination with current and future observatories Immediate feedback More robust data Fewer consumables, logistics Constantly available VLBI network Monitoring: for example astrometry Spacecraft tracking Growth path for more bandwidth More sensitive astronomy

13. huib 1/3/08 13/19Geant, Bled, Slovenia, March 4 2008 Link to China Miyun Urumqi Seshan Kunmin TEIN2

14. huib 1/3/08 14/19Geant, Bled, Slovenia, March 4 2008 Long-haul connectivity Important milestone: can be done! Across cultures and firewalls... Long round trip time was a real challenge Cannot be done with TCP/IP UDP over light-paths Done a few more tests Arecibo on Puerto Rico Done correlation of Australian antennas Yielding unique astronomy results And China of course Small test to Chile Must do more To South-America To South Africa Most US antennas are not connected!

15. huib 1/3/08 15/19Geant, Bled, Slovenia, March 4 2008 Doing R&D for future e-VLBI 10 Gbps connectivity coming up Development of data acquisition system required Interface to UK eMERLIN system Connectivity to Onsala (SE) telescope And Metsahovi (FI) Working on distributed software correlator Prototype operational for quality control Grid enabled Looking for P-ops regime Not sure this is cost effective Power and cooling bill

16. huib 1/3/08 16/19Geant, Bled, Slovenia, March 4 2008 Roadmap of future telescopesLOFAR SKA and SKA pathfinders

17. huib 1/3/08 17/19Geant, Bled, Slovenia, March 4 2008 What we achieved & learned e-VLBI is an operational, robust facility in Europe Enabling unique science from the start Reaching competitive level with all telescopes and 1 Gb/s for any science application Requires light-paths for optimal performance Had to overcome some network quirks for special applications But when it runs it really flies on Geant! Can do even intercontinental VLBI Were able to overcome problems with delays e-VLBI is the grow path for more sensitivity And global VLBI!

18. huib 1/3/08 18/19Geant, Bled, Slovenia, March 4 2008 Wish list... Light paths, probably dynamically allocated To accommodate distributed correlation And around the globe in some uniform manner Must continue close collaboration with NRENs/GEANT Will use 10Gb/s to make fellow astronomers forget conventional VLBI... but not quite ready for that Considering some improvements in VLBI architecture: Buffering data at telescopes and correlator for robustness Maybe involve more supercomputing/GRID in the future? Must address a number of things at astronomy side Decide on correlator architecture for next generation Keep a focus on Global e-VLBI, incl NRAO antennas in the US Develop common ground with E-LOFAR Continue to explore technological synergy with SKA

19. on behalf of EXPReS partners: and: all our friends at NRENs