Correlator overview

The Correlator, or the EVN MkIV DataProcessor at JIVE as it is officially called, consists of a correlator that is fed by 16 data units via 16 station units. Normally the system is operated by a team of three men for 80 hours a week, but during e-VLBI sessions the system is manned fulltime. The operators use the JIVE Correlator Control Software programs to run correlation jobs and monitor their progress.

Each data/station unit pair can relay data from a single telescope at a rate of 1 Gigabit per second distributed over 16 subbands. Usually the data are recorded at the telescopes on disk packs in Mark5 units, sent to JIVE, and played back on the Mark5 units there. But the Mark5 units can also be operated in e-VLBI mode; then they stream the data in real time from the telescopes via fiber connections to the station units at JIVE. The station units reorganize and synchronize the data streams and feed them to the correlator.

The correlator can make a quarter million complex lags, but these have to be distributed over all station pairs, subbands and polarizations you want to correlate. The whole correlator can be read out in 0.25 second putting up to 6 Megabytes per second into the post processing system. For more details see the Operational status of the EVN MkIV Data Processor.

Then the JIVE support scientists take over. They inspect, calibrate and correct the data with the help of a pipeline processing program, and deposit the results in the EVN Data Archive at JIVE. From there the astronomers can download their data together with the information added by the support scientists, and do the final processing "at home".

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