Gbps fringes

Experiment DT005 was a 1 Gbps test carried out on 12 March 2003 involving Metsahovi and Jodrell Bank observatories at 22 GHz. The recording system was based on the equipment developed in the PCEVN project that has proven to be extremely robust. The data were recorded using 2 PCs at each station (32 tracks recorded on each PC at 16 Mbits/sec/track). This gave 16 channels of LCP data, each with 16 MHz bandwidth. The output from each 'headstack' on the MkIV formatter was sent to a different PC. The data were afterwards converted from PCEVN format to Mk5 format at Metsahovi and ftp-ed to JIVE for correlation using Mk5 units to play back the data. The 32 tracks from each 'headstack' were correlated in separate passes.

This represents a number of firsts for the EVN, the EVN data processor at JIVE, and most likely for the VLBI community in general:

• First international 1Gbps fringes, Mark5-style.
• First 1Gbps e-VLBI fringes in EVN.
• Use of FFT on sampled Mark4/Mark5A data to verify data quality.
• Correcting data format problems in "raw" VLBI data using software reformatting.
• First fringes at the EVN Data Processor at JIVE from data recorded at 18 Mbits/sec/track.
• First fringes at the EVN Data Processor at JIVE from data recorded at 1 Gbps.
• Verification of e-VLBI interoperability between PCEVN and Mark5A.

Below are a couple of examples of the resulting fringes (one subband from each 'headstack', subband numbering begins at 0) shown as amplitude in delay and delay-rate space. The fringe is clearly detected (highlighted in red) on both headstacks.