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29 January 2007 e-VLBI Test

Date: 2/6/2007 6:58 PM
Subject: EVNtech: e-VLBI Jan 07 *and* first 512 Mbps 5-station fringes
Attachment: 3c454.3_ed.jpg

Hi all.

Last week saw the first e-VLBI run of 2007. This session was set up as a double adaptive run (Jan 29 - Feb 1), in which the first run was to be used to select the target(s) for the second run. It is hoped that this mode will allow unique observations which can only be done using e-VLBI.

One proposal was accepted. This proposal had as aim to survey 16 relatively little studied radio emitting X-ray binaries, and to perform full (~10 hour) observation of targets in an active or flaring state.

As it was essential for the data of the first run to be reduced as quickly as possible, the PI was present during the observations and the data reduction was carried out on-the-fly.

The usual 6 stations participated, Wb, Cm, Jb, Tr, On and Mc, at a data rate of 256 Mbps. The first run was to last from Jan 29 12:43 UT until 1300 UT the next day. A few problems were encountered. Tr could not send any data at the start of the run because of routing problems in Poznan; this however was soon fixed. Throughout the run, Mc would occasionally drop out, although we had tested the connection successfully at 512 Mbps just the previous week. Changing the station unit that Mc was connected to did not solve the problem; later on however we realized that we had run into some unfortunate combinations of hardware (station unit-Mark5). Only modest amounts of data were lost because of these problems. Cm had technical, not e-VLBI related issues, resulting in all data being lost.

At a technical and operational level, the observations went extremely well. No serious problems were encountered, re-starts of the correlator and mark5 units were few. Also the reduction strategy worked well; by the end of the first run, pileline maps had been produced for 14 out of 16 sources.

Unfortunately, none of the sources were found to be in an active state. As a consequence, the second run was cancelled.

We did however manage to reserve four hours of test time with all telescopes on the 2nd of February. During this test, in which we observed a strong calibrator source, we did a one hour 512 Mbps run with 5 stations (Tr unfortunately could not sustain this data rate). The resulting map is appended to this message.

512 Mbps from Mc has only been possible since we replaced the motherboard in one of our Mark5s, so we swapped Tr to this Mark5. This caused no end of problems with routing and ip addresses. When this was solved, we managed 480 Mbps from Tr. Possibly a motherboard upgrade at Tr will do the trick.

To conclude, operationally and technically this run was highly succesfull, and on top of it we got our first 512 Mbps fringes to 5 European stations. Scientically it was of course slightly disappointing, but at least we have clearly demonstrated the feasibility of this type of observations.

Regards, Arpad

expres/sa1/29jan07_test.txt · Last modified: 2007/05/11 16:15 (external edit)