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September 03, 2007
ORIENT, GÉANT2 Link World's Largest Telescope
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Aug. 29 -- Radio Astronomers from Europe and China have for the first time used the trans-Siberian ORIENT circuit to connect telescopes thousands of miles apart, demonstrating what can be described as the world’s largest telescope.
The ORIENT circuit linking together Chinese networks, CERNET and CSTnet, and the European GÉANT2 network and its Dutch partner SURFnet, allowed high-speed transfers of astronomical data from a Chinese telescope to a supercomputer in the Netherlands. The use of ORIENT not only brings high network capacity, but also, by using the most direct route possible from China to Europe, reduces the time taken by the data to reach Europe by half compared with trans-Pacific routes.
Collaborators in the EXPReS project (Express Production Real-time e-VLBI Service) conducted the first successful e-VLBI observations to jointly use telescopes in China and Australia, China and Europe, and for a brief period Australia and Europe. The observations were demonstrated today by the Joint Institute for VLBI in Europe (JIVE), in partnership with their European VLBI Network (EVN) colleagues in Europe, China and Australia, to advanced networking experts at the 24th APAN (Asia-Pacific Advanced Network) Meeting in Xi'An, China.
e-VLBI, or real-time, electronic very long baseline interferometry, is a technique by which widely separated radio telescopes simultaneously observe the same region of sky, and data from each telescope are sent in real-time to a central correlator via high-speed communication networks. The correlator is a purpose-built supercomputer which analyzes the data to allow researchers to map the sky. The correlator can produce data with up to one hundred times better resolution than the best optical telescopes. In other words, this technique creates a virtual single telescope with an observing area equal to the distances separating the actual telescopes.
When data from the telescopes are sent electronically via fiber optic network, they can be correlated in real-time by the central processor at JIVE. This technique, known as e-VLBI, is ideally suited to observations of transient events such as supernova explosions and gamma-ray bursts. Astronomers receive data quickly and can plan follow-on observations accordingly. This is an improvement on the traditional VLBI process of shipping hard drives to the correlator, which can take weeks for delivery alone.
In preparation for today's demonstration, data were recently obtained using European, Australian and Chinese telescopes in separate tests. Today's demonstration, however, provided the first real-time correlation results from China-Australia, China-Europe and Australia-Europe baselines.
The observations were conducted by JIVE staff members in collaboration with their European VLBI Network (EVN) partners in Europe, China and Australia. Participating radio telescopes included the Mopra and Sheshan telescopes during the Chinese-Australian part of the experiment, and the Sheshan, Darnhall, Jodrell Bank, Medicina, Torun and Westerbork telescopes in the European-Chinese part.
Data were transferred to JIVE at a rate of 256 Mbps per telescope. Mopra was connected directly to JIVE through a dedicated 1-Gbps lightpath set up by the Australian, Canadian and Dutch national research and education networks (NRENs) AARNet, CANARIE and SURFnet, respectively. The Sheshan telescope was for the first time connected via the Chinese NRENs CSTNET and CERNET, the new high speed route across Siberia provided by the EC-sponsored ORIENT and TEIN2 networks, the pan-European GÉANT2 network and finally SURFNet. Most of the European telescopes have been connected for some time via dedicated lightpaths provided by the GÉANT2 partners.
"Getting this connectivity was not only a major technical achievement. It shows how a project like EXPReS can achieve things even beyond EC boundaries," said Huib van Langevelde, director of JIVE, an international institute to which the National Astronomical Observatory of China directly contributes.
Additional tests with telescopes in Puerto Rico and Chile are
planned for the near future. EXPReS aims to implement up to 16
simultaneous 1 Gbps-network connections between the central processor
at JIVE and partner telescopes across Europe, Asia, Australia, South
Africa, South America and the United States by 2009.
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Source: GÉANT2
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