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

Alan R. WhitneyMIT Haystack Observatory

Optical Waves: Who Needs Them and Why?Internet2 Fall Member Meeting

Chicago, IL5 Dec 2006

Traditional VLBIThe Very-Long Baseline Interferometry (VLBI) Technique(with traditional data recording)

The Global VLBI Array(up to ~20 stations can be used simultaneously)

Chautauqua 2001

Quasars, hotspots, polarization

VLBI astronomy example

ASTRONOMY• Highest resolution technique available to

astronomers – tens of microarcseconds• Allows detailed studies of the most distant

objects

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 Science

Plate-tectonic motions from VLBI measurements

e-VLBI Data Rates and Volume

• Typical astronomy experiment at 1 Gbps/station– ~10 TB/station/day– Global 20-station experiment ~200 TB/day– Single 10-day experiment can produce up to 2 PB

• Higher data rates yield higher signal-to-noise ratio in final results• Data rates of 8 to 64 Gbps are already on the horizon and can only be

sustained by e-VLBI too much data to economically record and ship

e-VLBI Characteristics

• Experiments scheduled well in advance; duration typically several hours to several days

• Data rate is constant over long periods of time; typically 128Mbps to several Gbps, extending to many Gbps in future

• Data are uncompressible white Gaussian noise• For real-time processing, latency must be typically <~1 sec• Some data loss (up to a few percent) can usually be tolerated• Intermediate network storage may be useful in some situations

These characteristics are well suited to using optical waves

International e-VLBI Demonstrations in collaboration with DRAGON project

• 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

Challenges of e-VLBI over optical waves• Easy and reliable scheduling• Easy setup and teardown of optical circuits• Quick identification and resolution of problems; all telescopes must

be connected all the time for real-time processing• Physical connection of remote telescopes to high-speed networks

with optical-wave capability; proceeding well in Europe, Asia and Europe – U.S. lags

Bottom line: e-VLBI and optical waves are clearly a good match and are already being successfully exploited on a limited basis for better science.