To: Liuzzo Subject: EL040G Dear Elisabetta, I have examined your project EL040G, observed on 28 February 2011, and the data are ready for distribution to you. Probably the easiest way to access the data is to download them directly from the EVN Data Archive (see below). Please let me know if you would like to do this and I'll be happy to assign a username and password to your experiment. Since your experiment included the phased array Westerbork, it may be possible to provide you the Wb synthesis array data in IDI FITS format, which may prove useful for the amplitude and polarization calibration of the VLBI data set. The experiment scheduled the following telescopes: JbWbEfOnMcTrSvZcBdUrSh. Please note that Ef recorded the data with both the regular MarkIV recorder and their new dBBC. The raw data of the dBBC have been included in the correlation, labelled Ed, so that you can pick the set of Ef data that you'd prefer to use. Your experiment was processed with the following parameters: 11 Tels (+Ed), 8 band X 2 pols, each with 16 points, 2 sec int. Please note that the originally recorded disks from the stations can be released after two weeks. If you have any questions, contact us at jops@jive.nl. EVN and Global VLBI Observations correlated at the EVN MkIV Data Processor at JIVE are now automatically calibrated via a pipeline process. You will receive email notification when the pipeline is complete. In particular, the a priori amplitude calibration table (and the associated, final ANTAB file), plus various other tables and plots will be available to download from the EVN archive (subject to the EVN Data Archive policy as discussed below). A description of the pipelining process can be found at: www.evlbi.org/pipeline/user_expts.html The EVN data archive at JIVE is now a central location for obtaining the information you need in reviewing your project. You can find network feedback from the stations, standard plots from the correlation review done here prior to distribution, pipeline results, and the FITS files themselves. Contact your support scientist to arrange for a password with which you can download your FITS file(s) from the archive directly. See the EVN Users' Guide in www.evlbi.org for a link to the EVN Archive policy -- in short, data from sources you identified as target/private in pre-correlation e-mail will not be made public, nor will pipeline images be available from them, for one year from distribution. The archive can be accessed via: www.jive.nl/select-experiment (or via the menu items of the main jive page www.jive.nl). Once in this portal to the EVN data archive, you can click on your experiment in the pull-down menu in the "Select Experiment" window; then click on the link "Show Experiment" that will appear immediately below this. You will then see a new window for your experiment, from which you can select from the various sorts of data available from the menu row along the top: *) Station Feedback = information provided by the stations' VLBI friends about the conduct of the experiment *) Station Logfiles = sched-based files you uploaded to VLBEER, observing log-files from the stations, other unprocessed station-generated files. *) Standard plots = the plots described below in a variety of formats, a copy of this cover letter *) Pipeline = pipeline plots; the ANTAB & UVFLG files used in pipelining *) Fitsfiles = FITS files, plus an associated README in case there are multiple correlator passes each with its own set of FITS files. JIVE also invites PIs to visit Dwingeloo in order to analyze EVN data. Financial assistance may be available to some projects (i.e., those meeting RadioNet trans-national access eligibility criteria) for visiting JIVE or other EVN institutes. Contact campbell@jive.nl for more details. Papers that result from your EVN observations should carry the standard EVN acknowledgment: The European VLBI Network is a joint facility of European, Chinese, South African and other radio astronomy institutes funded by their national research councils. General Remarks: ================ In the process of checking your experiment I have created plots of the weights vs time, auto- and cross-correlation spectra for a few one-minute intervals, and the behavior of amplitude and phase in time. These plots and an explanatory description can be found in your experiment's standard plots section of the EVN data archive. As part of the check-out procedure, I evaluate the quality of all data with low weights and set an appropriate cutoff for flagging. In this experiment the cutoff was set to the default value at 0.4. Since you observed with 2-bit sampling, your data have been corrected with an improved van Vleck correction to account for the statistics of high/low bits for each BBC's data stream at each station. Thus you shouldn't run ACCOR in AIPS. It should be okay to use autocorrelations for bandpass corrections or to use ACFIT. Remarks on plots or individual stations: ======================================== Jb: reported brief loss of data at 03:23 UT due to a control problem Ef: observed with MkIV (= Ef) and the new dBBC (= Ed), swapped polarizations in the dBBC were fixed during the correlation stage On: missed scan #01 Mc: bandpass limitations lead to a very low amplitude in subband 0 and a sharp drop in amplitude in the lower part of subbands 1 and the upper part of subband 7, as a result, subband 0 was flagged automatically; RFI as usual All plots discussed here were made while the data were still in an aips++ measurement set prior to conversion to a FITS file. The names of the plot files in the archive are: el040f-weight.ps station weight vs. time el040f-auto-[1:3].ps station autocorrelation amp vs. freq el040f-cross-[1:3].ps Ef-* baseline amp/phs vs. freq el040f-ampphase-[1:3].ps Ef-* baseline amp/phs vs. time weight vs. time: ---------------- The standard weight plots show the weights of the whole experiment, with each 1s integration plotted as a separate dot. The IF/polarization color-scheme is found at the bottom of the page. The IF/pols are drawn in this order, and points overplot. Before making the FITS files, I flagged weights at 0.4. This means that integrations with weights < 0.4 are in the FITS files, but with negative weights. Sv stopped recording at 21:46 UT, probably due to Mark5 problems. Missing data at Sh, Ur and Bd show the time ranges when the sources were below the horizon at these stations. autocorrelation spectra: ------------------------ The autocorrelation spectra show 1min of data taken near the middle of the scans on the fringe finder '4C39.25'. There is low-level RFI at almost all stations. The bandpasses look generally stable apart from some time-variable RFI. Subband 0 of Mc has been flagged (see comments above). The data have been corrected with an improved 2-bit van Vleck correction to account for the statistics of high/low bits for each IF's data stream at each station. Thus ACCOR shouldn't be run. It should be okay to use autocorrelations for bandpass corrections or to use ACFIT. (The plots were made after applying the 2-bit van Vleck correction.) baseline spectra: ----------------- The baseline spectra show amplitude and phase for baselines from the reference antenna Ef to any other participating station for the same time ranges as the autocorrelation spectra. Subband 0 of Mc has been flagged. In general, the amplitudes are constant and at about the same level, except for Sv/subbands 0,1,4, Jb/subband 5, Mc/subband 2 and Tr/subband 1. The phases of the two correlated polarizations are flat across the bandpass. amplitude and phase vs. time: ----------------------------- The ampphase plots show amplitude & phase as a function of time in the vicinity (~1.5hr) of the selected scans for baselines from Ef to any other participating station. The per-source/IF/pol color coding is as annotated. Each integration is plotted as a separate dot. The range of frequency points over which the vector averaging was done is annotated at the top. Subband 0 of Mc has been flagged. The amplitudes look stable. Even in the uncalibrated data, the phases of the fringe finder and the phase-reference sources can be followed easily, except for Bd at 01:30-02:30 UT, when the sources were at very low elevations. A few stations may have had startup problems, resulting in bad phases at the beginning of the very first scan. Good luck with the data reduction and analsis! Best regards, Stefanie