Status of EVN Amplitude Calibration --------------------------------------------------- The following table shows the median absolute amplitude error for EVN stations in the last session of 2008 (October). These results were derived from the pipeline amplitude self-calibration results of all EVN experiments which have been pipelined to date: 7 April 2009. The number in brackets after each entry is the number of experiments that were used to determine the median error for that entry. ------------------------------------ Station 18 cm 6 cm ------------------------------------ Cm Ef 0.03(5) 0.03(7) Hh Jb 0.19(4)* 0.08(6) Mc 0.06(5) 0.05(7) Nt 0.09(5) 0.15(7)* On 0.04(5) 0.14(3)* Sh 0.16(3)* 0.06(3) Tr 0.06(5) 0.03(7) Ur 0.05(5) 0.03(5) Wb 0.04(5) 0.03(7) Mh Ar Ys ------------------------------------ The blank entries indicates insufficient data. The numbers above are the median absolute error in the antenna gain amplitude (as calculated from pipeline amplitude self calibration). A value above 0.1 indicates a significant error which should be investigated. In addition to the absolute errors summarised here, the EVN pipeline provides details on every experiment processed at JIVE including the sign and time variability of the errors. The experiments included in the statitical analysis were N08L3, EK026, EF021B, EK028C, EZ018B at 18 cm, and N08C3, GP047, EF021A, EK028B, GC031B, EL036B, EZ018A at 6 cm. In each experiment, the self-calibration results of all the available bright sources were used to get the reliable results. *Sh: provided long baselines for EVN. Usually, the solutions of selfcalibration are reliable only with strong and compact sources by pipeline. Here, the true error might be smaller than the above value. Furthermore, it was found that it lost fringes at 1.3 cm due to the poor pointing caused by a mechanical problem (loose screws). The previous 18 cm expriments may be affected too. *On: maybe because of the strong wind and mechanical problems that were reported many times in the feedbacks. Due to the problems, it also lost four 6 cm experiments. *Cm: the rad files are available for the amplitude calibration. It is under investigation how to convert it to the antabfs file. *Jb2: strange Tsys curves in some experiments. Jb2 has noticed something wrong with the tpi values for EF021B and EB037D, and has started to investigate the problem after the session. Points of note: Results are similar to those reported previously, but some improvement is noticed for most stations in particular TR station at 18 and 6 cm. RFI seems to be the major source of errors at L band. Calibration at this frequency is variable with occasional experiments having quite large errors. However, most L-band experiments give good results at most stations. Most stations has a good amplitude calibration at C band in the session. However, it is still a hard work for some stations to maintain a good performance from session to session. It is under investigation which stations provide opacity corrected gain curves at K band now. So far, On, Sh, Ef and VLBA has claimed that they had made opacity-corrected gain curves. Robledo and Yebes reported that their gain curves were not opacity free. Stations provide Tsys measurements immediately after the e-EVN runs. This extra effort is highly appreciated. The a-priori amplitude calibration of the e-VLBI data is somewhat poorer due to the fact that there is no ampcal session before the e-EVN runs. The station gains are now improved at JIVE using amplitude calibrator sources before the data are released to the PI. Jun YANG for the Science Operation and Support Group (JIVE)