1. VLBI/e-VLBI An Introduction for Networkers Tasso Tzioumis, ATNF, CSIRO

2. Outline Caveat: A Basic introduction –Not a review of the latest techniques and results Radio Interferometry & VLBI Why: Science with VLBI How: Technology e-VLBI: Impact

3. Radio Interferometry Simple Interferometer Fringe Pattern Baseline B: Distance between antennas “Virtual” telescope of diameter B.cos  (projected baseline) Fringe pattern provides information on structure and position of the radio source

4. Earth Rotation Aperture Synthesis uv- diagram Baseline length and orientation (as viewed from the source) changes as the Earth rotates  new information on source structure. uv-diagram - an indicator of imaging “quality” of an array of antennas more antennas  filled uv  better image fidelity

5. Connected Element Arrays VLA Baselines up to 10s of kms “Real-time” detections Full-time operation ATCA

6. MERLIN Baselines 5-200 kms Radio-linked  “real-time” Operation e-MERLIN - fibre links under construction

7. VLBI Arrays

8. LBA x New Norcia x NTD

9. VSOP

10. Resolution Jupiter and Io as seen from Earth 1 arcmin 1 arcsec 0.05 arcsec 0.001 arcsec Simulated with Galileo photo Atmosphere gives 1" limit without corrections which are easiest in radio

11. Why? Unique VLBI Science Zooming in!

12. Cen A

13. Active Galactic Nucleus Mode l Hercules A

14. 3C236

15. Superluminal motion

16. Wide-field Imaging - surveying

17. Gravitational lensing Double-quasar 0957+561 - VLBA+EVN, 18cm PKS1830-211 Einstein Ring MERLIN, 5cm

18. NGC 4258 Galaxy with disk Radio continuum jet Jet on one side obscured H 2 O masers Continuum amplifies maser emission (in green) Tangential to disk maser emission – faint red & blue spots at Keplerian (point mass) rotation First real measurement of nuclear Black Hole mass Add time dimension (4D): geometric distance! –Image courtesy: Lincoln Greenhill

19. M82 Starburst

20. SN1993J Bartel et al

21. Mira Variable TX Cam 43 GHz SiO maser emission around a star No continuum emission at all Actually many frequencies with masers; composite movie! –Image courtesy: Phil Diamond &Athol Kembal

22. SS433 X-ray binary Precessing jets 0.26c jet speed Baryonic jets Model Movie of VLBI Observations

23. Astrometry & Geodesy Baseline Length Baseline transverse 10 cm 1984-1999 Fundamental reference frames –International Celestial Reference Frame (ICRF) –International Terrestrial Reference Frame (ITRF) –Earth rotation and orientation relative to inertial reference frame of distant quasars Tectonic plate motions measured directly Earth orientation data used in studies of Earth’s core and Earth/atmosphere interaction General relativity tests –Solar bending significant over whole sky

24. SGR A* - The Galactic Centre Measures rotation of the Milky Way Galaxy

25. Spacecraft Navigation Astrometry relative to background radio sources Can measure micro-arcsecond position differences Huygens spacecraft at Titan: –January 2005, VLBI tracking –Determine probe position during descent –Accuracy ~1 km –Fringes detected but data still being reduced

26. How? - current systems Data recorded on tape or disk systems at < 1 Gbps Transported (slow!) to correlator facilities Data processing by correlator

27. VLBI Recorders - Mkx

28. S2 VLBI Recorder LBA Disk system

29. The Future e-VLBI

30. e-VLBI global data transport

31. e-VLBI Science Impact Real-time operation (cf ATCA, VLA,…) –Fast response to “targets of opportunity” like flaring or exploding stars –Monitoring of evolving events –Immediate assessment of results Higher sensitivity from high data rates – imaging sources at the edge of the universe –Very high quality imaging –(very efficient way to increase sensitivity cf building larger antennas) Support high data rates of processed data –Facilitate “wide-field” imaging –Utilise GRID computing? –Database “mining”

32. SKA - an e-VLBI array? 1Tbit/s data transport requirement in inner array 100 Gbit/s data transport requirement in outer array SKA

33. Operational Impact Flexible scheduling –Fast response to astronomical events Robust operation –Real-time performance monitoring Immensely easier data transport Remote antenna operation Remote data analysis Distribution of processed data to users  Lower operating costs?

34. Summary VLBI offers a unique look at the universe - a “zoom” camera e-VLBI will revolutionise VLBI operations e-VLBI will enhance VLBI sensitivity, response time and flexibility SKA will be an e-VLBI array Networking is the future for VLBI

36. VLBA

37. The VLBA

38. EVN

39. Kx recorders