Dear PI, We have examined the data for project RDV23 on 23 Oct. 2000. 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/aspen6/astronomy/oct00/rdv23/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/aspen6/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 CTA26, 0552+398, OJ287, 4C39.25, 2128-123, 1803+784, and OQ208. 4. Cross-correlation bandpass plots were generated for all baselines to HN for scans on CTA26, 0552+398, OJ287, 4C39.25, 2128-123, 1803+784, and OQ208. 5. Gzipped PostScript plots of Tsys and other monitor data for each available VLBA antenna can be found at /home/aspen6/astronomy/oct00/rdv23. 6. The jobs associated with the correlation of RDV23 can be found at: /home/aspen6/astronomy/oct00/rdv23/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: 6920-6950 7. Operations staff have devised a web browser to navigate the file server aspen, 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.hmtl, initially under Reports and Memos 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 aspen. 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: RFI at most North American stations in IF channel 6. VLBA stations: SC: Low amplitude in IF channel 2. HN: RFI in IF channel 6 is affecting cross-correlated data. NL: OK FD: OK LA: Slightly variable weights at 0:00 - 10:00 UT; weights at 95%. No fringes at 20:02 - 23:27 UT; antenna was stowed. PT: Out with cryo problems at 13:45 - 21:15 UT. KP: RFI in all S-band channels. OV: Poor weights on forward passes at 13:45 - 20:00 UT; weights vary between 0% - 100%. Low amplitude in IF channel 7. BR: OK MK: In SEARCH at 23:30 - 0:00 UT; recorder problem. RFI in IF channel 5. Non-VLBA stations: GC: OK GG: In Search and poor weights at 13:45 - 14:15 UT; tape problem. Recorder problem at 20:30 - 21:15 UT and antenna problems at 3:30 - 12:30 UT; no data. Intermittent searching due to poorly known tape footages. Poor fringing seen in delay plots on several scans. HH: Poor weights at tape change at 1:00 - 3:00 UT; weights vary between 0% - 100%. KK: Poor weights at 13:45 - 3:00 UT; poor on track #33; tape moved with no improvement; tape problem. Out for intensive run at 18:00 - 21:00 UT. MA: RFI in all S-band channels. MC: RFI in all S-band channels. NY: Strangely shaped bandpasses at X-band seen in autocorrelation plots. TS: OK WF: Funny bandpass shape in IF channel 5 seen in autocorrelation plots. WZ: Out for intensive run at 18:00 - 20:15 UT. Variable weights at 2:00 - 14:15 UT; high errors on track #21; tape was moved with no improvement.