Status of EVN Amplitude Calibration --------------------------------------------------- Session 3/2009 --------------- The following table shows the median absolute amplitude error for EVN stations in the last session of 2009 (October). These results were derived from the pipeline amplitude self-calibration results of all EVN experiments which have been pipelined to date: 13 April 2010. 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 5 cm ---------------------------------------------- Kn 0.18(3)* Da 0.10(2) 0.22(4)* 0.17(4)* Jb 0.12(6)* 0.11(5)* 0.36(4)* Ef 0.04(6) 0.03(5) 0.06(4) Mc 0.08(6) 0.06(5) 0.07(4) Nt 0.07(6) 0.06(5) 0.13(4)* On 0.06(5) 0.06(4) 0.09(4) Sh 0.06(2) 0.08(4) Tr 0.08(6) 0.04(5) 0.04(3) Ur 0.04(4) 0.07(4) Wb 0.04(5) 0.06(4) 0.06(3) Ys 0.07(4) 0.07(4) Ar 0.09(1) Ro 0.08(2) Hn ============================================== 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: EB042, N09C3, GF015A, EB044A, and EB044B at 6 cm; ES062A, N09M3, ES063A, and ES063B at 5 cm; EC029A, EC029B, GF015A, EP067, EM078, and GV020A at 18 cm. In each experiment, the self-calibration results of a bright and compact source were used to get the reliable results. *Kn & Da: The SEFD value used for making dummy antab files are 600 Jy at 18/21 cm, 700 Jy at 6 cm, 410 Jy at 5 cm. *Jb: Lovell telescope was used at 18 cm. MK2 telescopes was used at 5 cm. Both were used at 6 cm. The Tsys scale factor for MK2 was ~1.8 at 5 cm in the Experiment ES062A & B and ES063A & B. *Nt: Tsys ~140 K at 5 cm. Tsys data had large variation from scan to scan, eg. ES062A. Points of note: Most stations kept good amplitude calibrations in Session 1/2010. Onsala reported a minor problem with its noise source during the session. As the noise source worked improperly, its Tsys curve showed a few clearly Jumps in some experiments. After carefully editing, these jumps were removed. After the session, a new noise source has been installed. RFI is the major source of errors in some side subbands at L band, e.g. Wb: median error of 0.7 at 1.61 GHz. In the latest Session of Mar 2010, the sampler statistics are available for stations to make the backend work at the best balance point to reduce sensistivity loss. Thank Aard Keimpema for the great work. Jun YANG for the Science Operation and Support Group (JIVE)