European VLBI Network (EVN)

The European VLBI Network (EVN) is the collaboration of major radio astronomical institutes in Europe that works together on the data collected by an array of European radio telescopes. The EVN also works with similar institutes in Asia and South Africa. VLBI (very long baseline interferometry) is a technique that involves the collection of simultaneous observations from these telescopes. Data is then correlated to form very sharp, high-definition images.

GÉANT is supporting the work of the EVN through the provision of network resources to allow rapid data transfer. Before it began working closely with GÉANT, data was collected at each telescope on magnetic tapes. The tapes were then transported by courier to the central correlator at the Joint Institute for VLBI in Europe (JIVE) in Dwingeloo, the Netherlands - a journey which could take up to six weeks.

If any of the telescopes were malfunctioning, it would be weeks before the problem was diagnosed. In addition, exciting astronomical events were often over before astronomers even knew of their existence.

The use of GÉANT and the national research and education networks in participating countries enables significantly faster processing and correlating of radio telescope data. Data can now be transferred almost instantaneously via the national research networks and GÉANT. It can therefore be immediately correlated and processed, producing images in near-real time.

The electronic VLBI (e-VLBI) that is thus made possible allows rapid follow up of significant astronomical events and permits telescope troubleshooting to occur in near-real time. The large amounts of data that can be transferred by the networks allow very sharp, bright images to be formed. Ultimately, the effect of using the networks to perform VLBI allows Europe's radio-astronomers to see further back in time.

As well as supporting the VLBI technique, GÉANT can also open the way for astronomers all over the world to access the data and images produced at JIVE. This method, known as “reverse e-VLBI”, transfers data from the central correlator in Dwingeloo directly to an astronomer’s personal computer for local study and analysis.