Subject: GM030B Dear PI, We have examined the data for project GM030B on 18 Feb. 1998. 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. 2. Delay, rate, phase, and amplitude plots were made for the observation. 3. Autocorrelation bandpass plots were generated for all antennas for scans on 1803+784, 2007+777, 0917+624, M81. 4. Cross-correlation bandpass plots were generated for all baselines to NL for scans on 1803+784, 2007+777, 0917+624, M81. 5. Weather and Tsys plots for the VLBA antennas for your project will be sent with the data tape(s). NOTES: BR: okay FD: okay HN: Extremely weak fringes throughout project--high tsys due to snow & ice in dish. KP: Antenna autostowed several times for a few minutes-- see obs. log LA: High Tsys spike around 04:00 UT-- probably temporary bad weather (i.e., big cloud) MK: okay NL: okay OV: okay PT: okay SC: Dead track 13, 21:03-21:10 Y27: IFs #1,6,7: odd bandpass shape due to being at edges of Y27 bandpass. Complex bandpass calibration recommended. IF#8: Fully beyond Y27 bandpass -- no data. EB: okay NT: First tape (20:15-02:48 UT): Perfect playback Second tape (03:03-09:46): Tape in search 04:00-04:20, and tape has slightly weak track 23. IFs #1,2,7: Odd bandpass shape IF #8: slightly lower power than other IFs. Note on EVN feedback web page from Jean-Francois Desmurs: Regarding calibration: The ANTAB formatted file for this experiment can be found on Astbo1 in the feb98 directory under the name gm030b.antab. Read the comments in the file to get further information. ----------------------------------------------------------------------------- Subject: GG034 feedback Dear PI, We have examined the data for project GG034 on 14 Feb. 1998. 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. 2. Delay, rate, phase, and amplitude plots were made for the observation. 3. Autocorrelation bandpass plots were generated for all antennas for scans on J1159. 4. Cross-correlation bandpass plots were generated for all baselines to EB for scans on J1159. 5. Weather and Tsys plots for the VLBA antennas for your project will be sent with the data tape(s). NOTES: VLBA SC: OK HN: OK NL: OK FD: OK LA: OK PT: OK KP: OK OV: No fringes between EB and OV from ~ 2:49-3:41 UT. BR: OK MK: OK Foreign Stations EB: OK MC: OK WB: Beautiful weights. ON: Slightly variable weights during reverse passes. NT: Slightly variable weights at the end of forward passes. IF 1 is sloped compared to the other 3 IFs. JB: OK TR: Many dead and poor tracks. Weights vary from 0.1-0.5. Correlator operator's log says tracks 2,3,11,29 dead and tracks 6,15,17,28,31,33 are poor. IFs 1 and 3 are dead. SH: Poor weights around 0.5, tracks 28-33 dead, many poor tracks. IFs 2 and 4 are dead. Sloped bandpasses in IFs 1 and 3. ALL STATIONS: Good rates and delays on source J1159. -------------------------------------------------------------------------- Subject: GL022 Dear PI, We have examined the data for project GL022 on 17 Feb. 1998. 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. 2. Delay, rate, phase, and amplitude plots were made for the observation. 3. Autocorrelation bandpass plots were generated for all antennas for scans on 3C84, 3C345, DA193, and 4C39.25. 4. Cross-correlation bandpass plots were generated for all baselines to HN for scans on 3C84, 3C345, DA193, and 4C39.25. 5. Weather and Tsys plots for the VLBA antennas for your project will be sent with the data tape(s). NOTES: SC: OK HN: OK NL: OK FD: OK LA: Stalled at ~11:30-12:10 UT and ~7:20-8:00 UT; system rebooted at ~21:46-22:00 UT. PT: OK KP: Variable weights on last two reverse passes. No fringes between HN and KP at 2:17 UT on source 3C84 and again at 3:40 UT on source 4C39.25. OV: Poor on track #2 from ~11:15-12:15 UT. BR: OK MK: In search from ~8:00-9:00 UT. VLA27: Track #29 dead and track #28 poor from ~2:20-3:15 UT. Non-uniform bandpasses in IFs 1,2,6,7 and 8. Non-linear phase versus frequency dependence in IF 1 ( Recommend doing complex bandpass calibration). No fringes in IF 8 and only partial fringing in IF 7. EB: OK TR: Dead or very poor on most tracks through-out observation. NT: Power glitch at site; not in jobs from 10:49:09-11:37:30 UT. In search and poor weights at ~12:30-13:30 UT and ~22:45-1:00 UT. All stations: Most target sources very weak. Good rates and delays on strong sources. ----------------------------------------------------------------------------- Subject: GM033 feedback (EB) Dear PI, We have examined the data for project GM033 on 23 Feb. 1998. 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. 2. Delay, rate, phase, and amplitude plots were made for the observation. 3. Autocorrelation bandpass plots were generated for all antennas for scans on all srcs. 4. Cross-correlation bandpass plots were generated for all baselines to Y & GO for scans on all srcs. 5. Weather and Tsys plots for the VLBA antennas for your project will be sent with the data tape(s). NOTES: EB: Did not observe. The whole 18 cm session was lost due to some filter confusion; A copy of the email explaining everything will be included with the data tape. Y27: The source was below elevation limits from 00:00-03:03 UT. Tape intermittently in search for a few minutes here & there. Y27 has a 50 MHz bandpass, so IFs 7-8 have odd bandpass shapes, IF #1 displays no fringing in the cross-corr. plots, IF#2 displays no fringing for the lower 1/6 of the bandpass. IF#8 has low cross-corr. amplitude and no fringing for the upper 3/5 of the IF. Complex bandpass calibration recommnded. A little RFI on IF 3 in the autocorrelation plots. RO: The first two fwd passes & the last 3 rev. passes are overwritten; data unrecoverable. For the last 3 fwd passes, there are parity errors on all tracks-especially tracks 2,3,6,13,18,22,23 are poor. Before 03:25, when in sync, playback is good. A little RFI in the autocorrelation plots on IF#5. Fringes on the RO-Y & RO-GO baselines are a bit weak. GO: Source below elevation limits 00:00-03:20UT. A little RFI in the autocorrelation plots on IFs 4 & 6. Excellent playback except for the first fwd pass (overwritten, data unrecoverable, but source below horizon) and the last reverse pass, 05:36-06:00 UT- tracks 27-33 are poor. Also, the antenna had a pointing problem. A copy of the email explaining everything will be included with the data tape. Subject: V064B1 PI letter Dear PI, We have examined the data for project V064B1 on 21 Mar. 1997. 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. 2. Delay, rate, phase, and amplitude plots were made for the observation. 3. Autocorrelation bandpass plots were generated for all antennas for scans on 'all sources'. 4. Cross-correlation bandpass plots were generated for all baselines to SC,OV,LA for scans on 'all sources'. 5. Weather and Tsys plots for the VLBA antennas for your project will be sent with the data tape(s). NOTES: There are HALCA tracking passes for all 4 working tracking stations, Goldstone (GZ), Green Bank (NZ), Robledo (RZ), and Tidbinbilla (TZ). In something of a record-breaking occurrence, they all seem to have worked, and all show fringes. GZ - fringes near zero delay NZ - fringes near -300 nsec delay RZ - fringes near +100 nsec delay TZ - fringes near -250 nsec delay Discontinuities in the fringe signal on baselines to the Halca orbiter occur at each handoff from one tracking station to another, and at any dropouts in the phase-transfer link that occur during a tracking pass. Fringe fits should be broken at each such discontinuity to avoid de- correlation. This will happen automatically at handoffs because the tracking-station name assigned to Halca changes, but at link dropouts it is necessary to force an AIPS scan break by passing the following table to AIPS task INDXR via the INFILE adverb. SUBARRAY = 1 / 80 08:08:34.4 ! stn_id = RZ 80 08:29:26.4 ! stn_id = RZ 80 14:00:06.6 ! stn_id = GZ 80 17:03:12.7 ! stn_id = NZ / KP - There is poor recording quality on the forward passes on the first tape. On the second tape, which came from the other recorder, the recording was okay. This is a known intermittent problem. There also is fairly significant interference near 4810 MHz, in both polarizations, usually a little worse in LCP than RCP. In the last hour of the observation, it becomes very strong, strong enough to raise the system temperature. OV - There is one poor recording pass near the start of the observation, but everything is okay thereafter. EB - The residual delay is a bit high relative to the VLBA, about +350 nsec. There are two tape passes with poor recording between 0900 and 1000. The bandpass has a quite different shape from the VLBA passbands, and looks more like the output of the Mark IV baseband convertors. SC - Watch for slightly high rates (more than 10 mHz) at low elevations, apparently due to rain and humidity. Note that the VLBA observations did not start until about 0241, since the source was not up until then. Cross-polarized fringes were seen on all baselines in a test using the first correlator job (up until 0348). This includes the baselines to the spacecraft. Of course, for the spacecraft, it's quite possible that this is due to RCP leaking through the LCP system rather than "true" cross-polarized fringes. The April 20 VSOP newsletter claims that a memo describing the work of the VSOP Polarization Study Team will be posted on the VSOP WWW site this week (http://www.vsop.isas.ac.jp), although it had not yet appeared as of April 22. ----- End Included Message -----