To build a really big radio telescope, use glass

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by Stuart Corner

Friday, 20 June 2008

! Radio telescopes in China, Australia and Japan have been interconnected in real time for the first time using the optical networks of AARNet and its counterparts to enable very high resolution 'images' of remote celestial objects. Related stories AARNet offers 10Gbps access AARNet to set up IPv6 project group Internet ossifying, warns architect Western Australia Govt pumps A$20m into star trek Melbourne, San Diego researchers link via video wall Tasso Tzioumis, research scientist at the CSIRO said: "AARNet has made an invaluable contribution in allowing Australian researchers to collaborate with the international research community. By making their light paths available for the transmission of data, we have been able to produce significant research findings which would be almost impossible to achieve without a high-speed network of this nature." The resolution of any telescope, optical or radio, depends on the size of its 'lens': in the case of a radio telescope the length or 'baseline' of the receiving antenna array. A single radio telescope has, at best, an antenna array that is a few hundred metres wide. However by taking simultaneous observations from two or more radio telescopes in different locations and correlating the data from these it is possible to create a 'virtual' radio telescope with a baseline that is thousands of kilometres in length, increasing its resolution by several orders of magnitude. The technique is known as very long base line interferometry (VLBI). The problem is that radio telescope observations generate terabytes of data. Generally these data are collected on site on tapes or disks and shipped to a central location for correlating. The process is slow and cumbersome and does not enable an observation session to be modified according to the results of the observations, or for astronomers to respond to rapidly changing events in the heavens. The development of high-speed optical networks dedicated to research, such as AARNet in Australia and its counterparts in other countries, has enabled astronomers in these countries to link several of their telescopes in real time increasing the effective baseline of their telescopes. The technique is known as electronic VLBI (e-VLBI). It is now used regularly in Europe and was used for the first time in Australia in March 2007. Radio telescopes at Narrabri, Coonabarabran, Parkes and Hobart were connected in real-time to a software correlator at Parkes, at speeds up to 256Mbps. This correlator was developed by a team at Swinburne to run on a general purpose super-computer and frees VLBI from the large and expensive hardware correlators used in the past. Observations were made over three days and the results submitted for publication within three weeks, a record for VLBI, according to AARNet. At the recent international e-VLBI Workshop in Shanghai the technique was extended to link five telescopes in Australia, China and Japan with the correlator at Parkes using AARNet3, the JGM2 network in Japan, China's CSTNet and the Pacific Northwest GigaPoP in Seattle. Results were fed back to researchers in Shanghai over the same network. The next development, according to AARNet CEO, Chris Hancock, is to streamline the process by which such networks can be set up. He said this one had taken "hundreds of emails" between engineers various networks over several weeks, and he was hopeful that it would be possible to create them almost on demand via a web portal. Please enable JavaScript in your browser to post your comment! Tags See All Tags AARNet  Astronomy  Radio Astronomy  Stuart Corner  Get stories like this delivered daily - FREE - subscribe now

 

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