Replacing tapes with fibre to create a real-time European Very long baseline interferometry NetworkBrussels 23 March 2001 The Grid, and especially high-speed networking, could allow to replace the current data transport of European radio telescopes, that uses magnetic tapes, by data transport through fibre. This would create a large Europe wide real-time radio telescope. This was explained by Richard Schilizzi from the Joint Institute for VLBI in Europe (JIVE) explained at the Grid workshop organised by the European Commission in Brussels in March 2001.
Although the observations of all the radio telescopes are done simultaneously, the data are not combined in real time. The bandwidth of the signals - up to 1 Gbit/s for each radio telescope - is too large for this. Data transport to the central data processing facility in the Netherlands at the Joint EVN Institute in Europe (JIVE) takes place via magnetic tapes that are sent after each experiment to JIVE.
The radio astronomers have started an investigation of systems to replace the current tape recorders in 5 to 10 years from now. A feasibility study at Jodrell Bank Observatory in the UK, one of the EVN institutes, has established that fibres are a viable alternative to tape recorders.
Currently plans are developed a pilot project to link 4 or 5 telescopes to JIVE followed by full implementation for the whole EVN. The pilot project would run at data rates of up to 2.5 Gbit/s per telescope and use IP for a maximum usable data rate of 1 Gbit/s.
A constant data transmission rate throughout an observation that can take up to 12 hours is needed, but service interruptions of a few minutes are acceptable. The experiment will use the European backbone, GEANT, for the trans-national links. Not everything is ready available yet: hardware and software interfaces from the telescopes to the data transmission system have to be developed.
Ad Emmen |
 |