Performance and Reliability of the EVN ====================================== EVN Session 1/2011 ------------------ The session consisted of four frequency blocks (18cm, 5cm, 6cm, 13/3.6cm). In each block, ftp-fringe tests and NME experiments were performed before the user experiments. Effelsberg had an improper cable connection (linked to the VLBA instead of MK4 port). This problem resulted in corrupt headers in N11L1. Cambridge was replaced by Kockin. As problems with automatically extracting ftp data, Torun manually extracted ftp data in NME experiments. There were 21 user experiments (8 at 18cm, 5 at 5cm, 5 at 6cm, and 3 at 13/3.6cm) including one ToO (RM006). There was three user experiment at 6cm done in the e-VLBI mode and three global VLBI experiments (GV020E, GC034E, and GC034F). There were four experiments (EY010D, EM080B, EW014, EY013A) correlated at Bonn and two experiments (GC034E and F) at Socorro. Station and correlator feedback for individual stations: Ef - All the baselines to EF (RR, all IFs) had un-periodic drops in phases at 18cm (caused by a loose connection?, not seen in Session 2/2011). Lost two-hour observation in EZ020C as problems with changing from pulsar to VLBI modes. Since 2nd March, they were running on "crystal clock" due to a problem with H-maser, there seemd no large difference after the change. Wb - The problem with measuring SEFD during the scan of weak sources has been solved via a new program. There was a clock jump of ~6.45us in EG052A. On - Bad weather was less reported (only seen in EG051B and EG053). The data was corrupted (low correlation weight and scan_check error report) due to bad MK5A recording for 2.5 hours in RM006. Tr - The problem with automatically extracting ftp data was seen often, such as in N11L1. Mis-set their LO by 4 MHz mis-set (5904 instead of 5900 MHz), which pushed their sky frequencies up by 4 MHz, placing them outside of the frequency range observed by everyone else in EG052A. Nt - One of the antenna wheels was damaged before Session 2/2010. There were no observations scheduled for Nt in Sessions 1/2011. Mc - The noisy and unstable auto-correlation bandpass shape reported earlier at 5cm was seen again and found out due to RFI. Ur - Participated all the experiments although it was listed as an optional station due to the limitation of the upcoming CE-2 observations. Sh - Only missed EY010D due to the CE-2 observations although its participation was not confirmed. Ys - Lost one hour observations in EG053 due to a problem of Field System. Mh - No scheduled EVN observations. Jb - Jb had weaker detection in LCP channels in EV018C. Kn - Fringes to Kockin had very low SNR in all the 5cm experiments. Ro - No required EVN observations. Ar - Participated in two EVN experiments: GV020E and EG051C. Good Fringes were also found. Hh - Mark5 disk pack failure caused loss of sources for 1.5 hours in GC034F. Bd - Unusual autocorrelation bandpass shape, reported earlier, seemed to be a feature of its BBCs. Zc - RCP channels have higher correlation amplitude than LCP channels at 6cm, as we knew in the previous session. Sv - The 6cm Fringes were quite weak in the LCP channels. This problem has been fixed in the later May/Jun Session. All the Russian stations have started to deliever MK5B data to JIVE in the EVN observations. Currently, there is no feedback on each experiment from them on the EVN feedback webpage. Furthermore, there is no daily averaged GPS data available in VLBEER. The new DBBC backend was put in some of the EVN user experiments to test its performance. Compared with old MK4 backend, it show an improved bandpass shape. The good sampler statitic distribution was also seen after N11X1. The Kunming 40m radio telescope participated in N11X1 and N11SX1 with the standard MK4 backend donated by the Westerbork observatory. Fringes to the Kunming station were clearly seen. The problem of strong DC component, revealed in the two NME experiments, has been solved recently (see the ftp fringe test CHIN05). Jun Yang Science Operations and Support Group (JIVE)