Dear PI, We have examined the data for project RDV26 on 12 Mar. 2001. The contact person for this project was Craig Walker. Here's a summary: 1. Tape weights vs. time plots have been generated for the entire time range of your experiment. These are a measure of tape record/playback quality, representing the fraction of valid data samples. Data with weights below 70-75% should be flagged. However, you may want to be more cautious when dealing with non-VLBA stations. The easiest way to estimate the best weight threshold is by looking at the tape weights vs. time plots generated here. You can find the weights plots at /home/vlbiobs/astronomy/mar01/rdv26/sniffer/final/wtsfile.ps. If your experiment involves more than one distribution tape then there will be a tape# subdirectory between /final and wtsfile.ps. See /home/vlbiobs/README.sniffer for instructions on how to interpret this plot. 2. Delay, rate, phase, and amplitude plots were made for the observation. 3. Autocorrelation bandpass plots were generated for all antennas for scans on 0420+417, CTA26, 0528+134, 0552+398, OJ287, 4C39.25, and 1921-293. 4. Cross-correlation bandpass plots were generated for all baselines to HN for scans on 0420+417, CTA26, 0528+134, 0552+398, OJ287, 4C39.25, and 1921-293. 5. Gzipped PostScript plots of Tsys and other monitor data for each available VLBA antenna can be found at /home/vlbiobs/astronomy/mar01/rdv26. 6. The jobs associated with the correlation of RD026 can be found at: /home/vlbiobs/astronomy/mar01/rdv26/jobs. These files provided the correlator with all ancillary data needed for VLBI, including: correlation parameters and telescopes correlated in the final production. The job numbers are: 6620-6643;6649-6650;6645-6646;6651;6648 7. Operations staff have devised a web browser to navigate the file server vlbiobs, as well as view and retrieve its text and PostScript files, gzipped or not. This browser can be reached through the VLBA homepage http://www.aoc.nrao.edu/vlba/html/VLBA.html, initially under Data Analyst but then under Aspen. All of the files mentioned above can be accessed either with this browser or by FTPing to the vlbiobs account on vlbiobs. Automated Calibration Transfer for VLBA Correlator Output --------------------------------------------------------- The first phase of automated calibration transfer for data from the VLBA correlator has been completed, and was used for your observation. This transfer of calibration information includes data from the 10 VLBA antennas, as well as selected information from the VLA and Effelsberg, which currently provide VLBA-style monitor data. Significant changes to AIPS have been required to introduce calibration transfer, so users must have the patched version of 15OCT98 AIPS, or any later version, beginning with 15APR99. Help files for a number of AIPS tasks have been updated to reflect the new calibration procedures. There also is a new version of the VLBI chapter of the AIPS cookbook, available from http://www.cv.nrao.edu/aips/aipsdoc.html, that includes more details on how to cope with the calibration transfer process. The calibration-transfer process relieves observers of the burden of creating and inputting calibration files for VLBA antennas. Instead, this information is now provided as tables attached to the FITS data sets output by the VLBA correlator. The ancillary data include antenna gain (GC table), system temperature (TY table), pulse calibration (PC table), flags (FG table), and weather (WX table). The wise observer will not modify these original tables; processing errors might then force the data to be reloaded using FITLD. See the description of MERGECAL in Section 9.2.1.7 of the new cookbook chapter for more detail. Of course, skeptical users can simply delete the appropriate tables created by FITLD and generate their tables in the old manner. Phase 2 of calibration transfer will include supply of data from more external telescopes, and probably will proceed incrementally, depending on both the availability of the external information and the implementation of new software in Socorro. At present, ancillary data from most external telescopes must still be loaded in the old manner, and observations of strong sources may be needed for manual pulse calibration at those telescopes. Up-to-date instructions on coping with observations including external telescopes can be found at http://www.nrao.edu/vlba/html/OBSERVING/cal-transfer/cal-transfer.html. Please send comments on calibration transfer to julvesta@nrao.edu, and send bug reports to daip@nrao.edu, with a copy to julvesta@nrao.edu. NOTES: General Notes: Many stations have slightly variable weights scattered throughout correlation; see weights plot for details. RFI at all North American stations in channel #7; known satellite downlink. Small intermittent RFI spike at many stations in channel #6, exact satellite causing this problem is unknown, but has been seen in previous RDV projects. VLBA Stations: SC: OK HN: Low cross-correlation amplitudes in channel 7 possibly due to the RFI. Increasing scatter and poor fringing to all stations at around ~7:30 - 13:00 UT; possibly due to snow at HN which was the reference antenna. NL: OK FD: OK LA: OK PT: OK KP: BBC #5 was dead. It has since been fixed. It is mentioned in the operators log, so it was noticed by the operator during observation. RFI in all S-band channels. OV: Track #2 is poor at 10:00 - 14:08 UT; this is a recorder problem which has a maintenance form written about it. BR: OK MK: OK Non-VLBA Stations: HH: Tape in and out of SEARCH at ~2:00 - 3:00 UT. See weights plot. KK: Site out for intensive at ~17:50 - 20:10 UT. Variable weights at ~3:15 - 14:08 UT; weights vary between 0% - 100%, but stay near 100% most of the time; tracks # 32 and 33 had high error rates; tape was swapped with no improvement. MA: RFI in all S-band channels in the autocorrelation plots. Poor fringing and low amplitudes in channel 5 probably due to the RFI. MC: RFI in all S-band channels in the autocorrelation plots. NY: Tape was not sent since the site was out for most of the observation. ON: Track #18 dead at ~1:35 - 1:50 UT; weights at 87.5%. TS: OK WZ: Variable weights at ~14:30 - 14:50 UT; weights vary between ~30% - 100%. Site out for intensive at ~18:00 - 20:10 UT. Variable weights at ~20:10 - 22:50 UT; weights vary between 50% - 100%; all tracks had low to high error rates; tape was swapped with no improvement; Tape statistic plots were sent to Steve Durand. Variable weights at 2:00 - 3:00 UT; weights vary between ~50% - 100%; tracks #9, 12 - 31 are were poor. See weights plot.