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Marathon e-VLBI run

Submitter: Zsolt Paragi
Description: There is an ever increasing demand on the European VLBI Network (EVN) to carry out high sensitivity observations, which means that huge amounts of data have to be recorded at the stations and shipped to the central data processor at JIVE. This problem is alleviated by the possibility of streaming data for some of the projects directly to the correlator through the Internet, using the real-time e-VLBI mode of the EVN. Normally there are ten scheduled 24-hours e-VLBI runs in a year, and in addition sometimes "target of opportunity" observations are carried out to follow-up on unexpected cosmic events.

Last week the e-EVN achieved a milestone, by operating almost continuously for 64.5 hours between 9 and 12 March 2011. During most of this time data were streaming at a rate of about 7 Gbits/s (see the network throughput graph). We started with performance checks of the European telescopes at Effelsberg, Jodrell Bank, Knockin, Medicina, Onsala, Torun, Yebes and Westerbork, as well as Hartebeesthoek in South Africa, and Shanghai in PR China. This was followed by a short check of Arecibo at a lower data rate. The science observations started on Wednesday late evening, including Shanghai and Hartebeesthoek, with a maximum data rate of almost 9 Gbit/s. The target source set for these two telescopes at around midnight, but later it was rising for Arecibo in the very early morning. On Thursday there was a short gap for changing the network setup (a bit longer than anticipated), and we continued with another science project lasting 48 hours.

The only major network problem was the loss of Onsala during Thursday night for several hours (drop in data rate is visible), which was fixed on Friday morning. Overall, this was a very successful e-VLBI science marathon run.
Copyright: JIVE
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