Message 12/446 Steve Parsley Oct 10, 2000 12:07:32 pm +0100 Date: Tue, 10 Oct 2000 12:07:32 +0100 To: , "Huib Jan van Langevelde" Subject: EVNtech: EVN MKIV CORRELATOR REPORT, TOG TORUN OCT 2000 Content-Disposition: inline Sender: owner-evntech@jb.man.ac.uk Precedence: bulk X-MIME-Autoconverted: from quoted-printable to 8bit by newton.astro.uni.torun.pl id MAA00879 EVN MKIV CORRELATOR REPORT, TOG TORUN OCT 2000 Steve Parsley, H.J.van Langevelde October 20 2000 INTRODUCTION In the past half year the correlator environment has matured considerably. All daily operations can now be performed by the correlator operators, giving the staff some time to concentrate on releasing user projects and making more modes available. SCIENCE OPERATIONS Production correlation of user experiments has been the main activity (60% of the 80 hr weeks) during the last 6 months. Around 25% of the correlator time is spent on testing, while the remainder goes into checking out experiments (clock searching and NMEs). During production we reach over 30% efficiency, which results in about 15 hours of effective experiment time per week. The operational efficiency was substantially decreased in the month of August, not only because of the holidays, but also because of a procedural error which lead to the recorrelation of 4 projects. In this 6 month period we completed 25 projects (16 user and 9 test/NME). By the end of the summer almost all data had been distributed to the users. We were able to release most of the tests, but only 3 user projects; these still require an agreement of the PI. A large fraction of the time is spent on various test experiments. There are still a few concerns about the data quality. We have concerned ourselves about how AIPS interacts with JIVE data, and fixed a number of things in that area. We are still investigating the data carefully to make sure no "byte slips" occur. This issue prevents us from automating the data quality control. When we have defined and implemented a set of standard plots, we will start releasing tapes automatically after a two week grace period. Ian "Max" Avruch is the new support scientist in the science operations group. TECHNICAL DEVELOPMENTS Progress was made to bring the number of "byte slips" events down, but further work to come to a robust solution is required. A long series of upgrades were necessary to make the system deal transparently with gaps between scans and different tape motions at individual telescopes (thick and thin). We convinced ourselves the EVN MkIV data processor at JIVE can deal properly with phase referencing experiments. Interpretation of early results was hampered by a either poor ionosphere (18cm) or limited accuracy of the telescope positions (6cm) The pulsar gating hardware was exercised and a test project was processed. It showed increasing signal to noise when the gates were made shorter as expected. Oversampling was tested successfully but the DSP project, which is required to use the full capacity of the correlator, was delayed. Unexpectedly high rates of head wear have been measured on the JIVE DPUs. The main suspect is humidity; the dry air supply system is under investigation. ============================================================= S M Parsley Technical Manager Joint Institute for VLBI in Europe Postbus 2, 7990 AA Dwingeloo, Netherlands +31-(0)521-596519 (direct), +31-(0)521-596500 (switch), +31-(0)621 201418 (mobile), +31-(0)521-597332 (fax) parsley@jive.nl =============================================================