ESG report for the CBD, 2005 November Performance and Reliability of the EVN ====================================== Session 2/2005 -------------- As far as ftp fringes concerned the session went well. However Noto dropped out from the session very soon, because the azimuth engine broke. Torun used Rubidium maser which is not stable enough for C-band, or phase-referencing in the L-band. In Effelsberg the MkIV formatter broke and three experiments were recorded on tape. The NMEs have been correlated and pipelined. The ERIs were the following: N05L2 - 0.90 (Nt was still OK); N05L3 - 0.52 (Nt, Ef, Mc failure); N05L4 - 0.67 (Nt out + minor failures); N05C2 - 0.59 (Noto problem + other minor failures). Although Mk5 recording is superior to that of tape, it seems a number of times recording stops ('Mk5 hangs'), and there is often trouble with the 'FS-Mk5 communication'. This can be best solved by rebooting the Mk5, which is time consuming. Occasionally there are bad disk packs. Cm - Trouble with the elevation engine in some experiments. It completely broke in ES054B, but the problem was fixed before the next experiment, N05L3. ES053B was a failure due to an error in the MERLIN control software: telescope stuck on one source. Had Mk5-FS communication problem in N05L4 - failure. Ef - Formatter trouble in ES054A, VC#6 and #8 lost. Formatter broke in ES054B - continued on tape (including three other experiments) till EVN spare arrived from Medicina. About half an hour data lost in EK020C due to Mk5-FS communication problem. Lost 20 minutes in EI008 due to FS crash. In EG034 data were lost from 02:16 UT till the end - again for a Mk5 problem. Wb - Accidentally overwrote EB030 logfile. Lost recording for about half an hour after bank switch in ES054A. Real time array control system got stuck for more than an hour in N05L4 - calibration data lost. Lost vacuum several times in GB049C. In EP049C also had trouble with recording, but now the Mk5 recording stuck (twice - more than an hour of data lost). Jb - ES053B was a failure due to an error in the MERLIN control software: telescope stuck on one source. Lost 10 minutes in N05C2 due to a bad disk pack - no other problems. On - Lost about 30 minutes in EB030 because Mk5 hanged. VC#2 was unlocked in ES053B. In EI008 scan_check could not deal with three scans. Mc - Was late from N05L3, recorded only from scan#40. Lost 2 hours in EJ007B due to an FS problem. In GB049C had to start late due to various technical problems. Nt - Observed successfully the first experiment only (N05L2). The first day of EK020B had trouble with the Mk5. Afterwards a failure of the encoder of an azimuth engine stopped the antenna. Could not fix the problem during the session. Tr - Used Rubidium frequency standard in the whole session, because the H-maser was sent for refurbishment to the manufacturer. Note that although Tr produced fringes, the C-band data will be useless due to the very short coherence time (we had the same problem with Noto in session 3/2004). BBC#3 unlocked all the time (rack-related problem, not the BBC itself). Ur - Observed according to version 1 of the block schedule, instead of version 3 - missed EK020C for this reason. Sh - No major problems reported. Hh - Lost more than an hour in EB030 because Mk5 failed to record after bank switch. Ar - FS lost contact to Mk5 in EK020C. About half of the experiment was lost. C-band ftp-tes showed fringes. GT006 went OK. Ro - Participated in ES054A. Apart from RFI and some antenna limitations, there were no problems. Session 3/2005 -------------- Session 3 went well. Apart from Noto not being able to join the observations, serious telescope failures affected only a couple experiments. The pre-session ftp test showed no fringes in the upper 4 channels in Shanghai, and a Mk5 problem in Westerbork. These problems had been fixed before N05C2, the first scheduled experiment. Strong winds and rain/snow caused some problems for Onsala in the C-band, and for Metsahovi in the K-band session. At the end of the L-band session Tr failed in three experiments. These were directly or indirectly related to a shortage of disk packs at the station. RFI around 1620-1630 MHz caused a lot of trouble for Westerbork (software/hardware problems in the tied array). There were six 1 Gbps projects in this session, five with Arecibo participation. Arecibo produced ftp fringes before these experiments. Besides the Jodrell Bank failure in GL028A (Lovell Telescope azimuth drive broke), there were no major problems reported. Robledo produced first ever 1 Gbps fringes in EP051, but it seems only in the lower half of the band (in the "headstack 1" channels). The C-band NME have been produced and pipelined. The L-band NME have been clock-searched, the K-band one not yet. The information below is drawn mainly from the station feedbacks, from the ftp tests, and from the NME reports. Cm - Had Mk5 communication problems in N05L5. Rack PSU completely failed during EP051, BBCs were unlocked. VLBA rack was no fixed by EA035A. Cm was not scheduled for other experiments. Ef - Had severe formatter communication problems throughout the session, but these did not seem to affect the data. Short segments of data lost here and there, due to problems with the Mk5. Pointing problems in EA035A, but only for a very short time. Wb - Could not play back from the Mk5 in F05C1 -borrowed a Mk5 from JIVE for the session. Had trouble with a file server, this caused minor problems occasionally. In EP053 observed the wrong version of the schedule (this was partly the PIs fault, who was very late with the schedule). Wb was three hours late in EP051. Jb - The Lovell Telescope was not available in the C-band session, used the small dish. Jb2 had occasional azimuth drive trips; in GB055A had low sensitivity. In GM057A the receiver lost vacuum (lost about an hour only). Sometimes had communication problems with the Mk5. The Lovell telescope azimuth drive had broke before GL028A. It was repaired halfway through the next experiment, EK022B. A couple of days later this repeated in GB055B -lost about 5 hours. On - No serious technical problems. Had bad weather, especially high winds in several experiments. This caused tracking problems. Had to stop in EP051 due to high winds. Mc - Produced first ever K-band ftp fringes, after a software correlator was discovered. Lost first half of EP051, because the antenna was not tracking due to an error in the antenna control unit configuration. Some scans lost in GV017B, due to "errors in positioning in schedule". Lost 2.5 hours in GM057B because of a power outage. Nt - The azimuth engine had been fixed just before the session. However, the schedules could not be run due to a "communication problem". Tr - Lost half an hour in GB052, due to "accidental duplicate mk5 process". Halfway through EP051, BBC#5 lost 1pps. Replaced this BBC after the experiment. Short off-source period in ES055 due to power outage. Did not observe GB055 because there were not enough disk packs (one unit sent from JIVE was broken -could not assemble a new one in time). Because of a Mk5 error, recording stopped in GM057B. In an attempt to restart it all previous data were deleted, including GV017B, that had been recorded on the same disk pack. Ur - Had trouble with the receiver in N05K2, and thus started a bit late. There were soem antenna problems in EM059A, the first scan was lost. Tsys was high in both K-band experiments. In N05L5 high polarisation leakage was observed -readjusted the converter unit after the experiment. In EK022A started recording late because of trouble with the power supply. Sh - The cryogenic system had stopped working before N05C3. Had high Tsys in the whole C-band and K-band sessions. In EP053 observed the wrong version of the schedule (this was partly the PIs fault, who was very late with the schedule). Some data were lost in EM059A due to antenna problems. Swapped pols at the beginning of the L-band session. Lost two scans in EK022B due to a Mk5 error. Hh - Started late in N05C3 because of a secondary reflector controller failure. The only user experiment EP053 went smoothly. Ar - In the GL028A-E 1 Gbps experiments had fluctuating levels and bad sampler statistics in the lower sideband of BBC#8. This problem was solved by GV017B. Produced 18cm ftp fringes, but failed in the 90cm ftp test. The reason was not entirely clear, but the spectra showed no phasecals. Ro - Produced first ever ftp fringes in N05L5. Participated in the first 1 Gbps experiment, and produced fringes. Apart from some RFI, there were no major problems in the NME, EP051 and GM057B. Experiment specific problems: In GB052 the pass length did not match the tape length. The last scan of each pass were lost in most cases. ES055 was scheduled as a single scan, which made disk pack change complicated. There were no Tsys measurements made during the experiment, since these are usually done in between the scans. Ftp tests --------- There were four ftp tests scheduled, and an additional one carried out before the 90cm session for the stations request. The file transfer has not been automated yet. Short files (1-4s) are routinely used. There was a new version of the NICT software correlator installed at JIVE. With this, 1 Gbps data can also be processed. This has been tested using data from EG034 and EP051. As from session 1/2006, the spectra of individual stations will also be included in the ftp test webpages. Phasecals will be easily monitored. K-band performance of the EVN ----------------------------- Andreas Brunthaler processed the K-band NME and wrote a report on K-band phase- referencing. It seems phase-referencing works well on the shorter baselines. The longest baselines need further self-calibration. Applying the polar motion model did not lead to significant improvements. The data have been insufficient for determining station-based zenith delay errors - this proved to be very effective in current VLBI astrometric projects. It was also investigated whether the K-band NME gain solutions could be used in user experiments. This was tested but did not lead to significant improvement. The gains are not stable, they often change significantly within a project.