18cm Session Subject: GS012A Feedback Dear PI, We have examined the data for project GS012A on 14 Sep. 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 0454+84,1946+7048,1819+6707,1600+7131,0513+7129. 4. Cross-correlation bandpass plots were generated for all baselines to HN for scans on 0454+84,1946+7048,1819+6707,1600+7131,0513+7129. 5. Weather and Tsys plots for the VLBA antennas for your project will be sent with the data tape(s). NOTES: 0454+84 & 0513+7129 are weak sources -> weak fringes BR: okay FD: dead track 9 (recorder problem at site) HN: okay KP: okay LA: okay MK: okay NL: okay OV: okay PT: okay SC: okay EB: okay TR: Bad tracks 26-33. Tape in search 9:15-9:30 & 14:37-14:41. IFs 2 & 4: bandpass edge problem or RFI near edge of bandpass IF #2: missing at 05:22 IF #2 & 4: missing at 08:53, 10:43, 16:11 WB: RFI spike on IF #1 Tape in search 5:30-5:40, 7:25-7:30, 9:22-9:24, 14:24-15:12. JV: did not observe correctly; terminal set to Mk III mode. JV was not correlated. Subject: V047R Feedback Dear PI, We have examined the data for project V047R on 14 Sep. 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 EB,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: Things look pretty good. Some problems stated below: Problems: MC and LA--RFI NZ -- interference in the first channel. This does not occur for GZ so this seems to be a problem at the Greenbank tracking station. TR -- DC spike in 2nd IF, which somtimes goes out Low wights, seems to be a recorder head problem Note: If the WTTHRESH parameter in FITLD is set to more that 0.5 most of TR data will be lost. Subject: GL021A Feedback Dear PI, We have examined the data for project GL021A on 15 Sep. 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 3C286, 1613+341, 1308+326. 4. Cross-correlation bandpass plots were generated for all baselines to HN & EB for scans on 3C286, 1613+341, 1308+326. 5. Weather and Tsys plots for the VLBA antennas for your project will be sent with the data tape(s). NOTES: Pass 1: Polar=Y, Cont., ffts=256, Spect.Avg=8, 8 Chnls: jobs 5820-5825. Pass 2: Polar=N, Line, ffts=1024, Spect.Avg=1, 2 Chnls: jobs 5840-5851. Pass 3: Polar=Y, Line, ffts= 256, Spect.Avg=1, 2 Chnls: jobs 5880-5887. BR: Pass 1: A little RFI on IFs 5 & 6 FD: Pass 1: Dead track 9 HN: Pass 1: Tape in search, 19:15-19:30 & 21:10-21:40 Pass 1: RFI on IFs 7 & 8 at 16:00 KP: okay LA: okay PT: okay MK: okay NL: All 3 passes: bad track 10, 04:16-04:25 OV: okay SC: okay Y27: okay EB: Slight bandpass edge problem (DC spike?), lower edges of IFs 2,4,6,8 GO: Pass 1: Dead track 2. IFs 5&6 missing Pass 2 & 3: Fringes on IF 2 only JV: No good data before 13:09. Pass 1: Dead track 22. Some RFI on IFs 5-8 at times. MC: Pass 1: RFI on IFs 1-4. Pass 2: Tape in search, 19:04-19:06 NT: The false start in the field system log caused errors to occur on our correlator. We had to hand-edit the log to get the job scripts to work properly. Joan Wrobel suggests, "If you lie to your computer, delete." Barry Clark simply recommends, "Do not lie to your computer." Tape in search for all 3 passes, 10:00-10:32 & 10:45-11:37. Pass 1: RFI on IF#8. TR: No data after 14:13 UT. Unrecoverable due to corrupted field system log after the 14:13 power failure. IFs 3,4,7,8 missing at 10:00 RFI on IFs 4 & 8 at 13:11 WB (WRT7): Tape in search for all 3 passes, 16:50-17:34, 18:02-18:37, 18:50-19:50 Pass 1: RFI on IFs 7&8 Subject: V047K Feedback Dear PI, We have examined the data for project V047K on 16 Sep. 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 EB 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: Experiment looks good except for these problems: Poor recording at JV and TR; it looks like the second channel is dead at JV most of the time. At TR the second channel intermittently dissappears. RFI at TR, JV, TZ all in the first channel. ON no fringes in second channel. Data missing from JV from 00:21-02:42 because of tape failures. ON stowed from 2:42-3:58 due to high winds. Note that if you set the WTTHRESH parameter in FITLD greater than 0.5 you will lose most of JV and TR. For more information on the performance of EVN stations see the EVN Experiment Facility (http://www.nfra.nl/jivebin/jiveese). For fringe plots of the HALCA via all the working tracking stations in your experiment see the NRAO Space VLBI webpages (http://www.aoc.nrao.edu/space_vlbi/aoc/ioc/frplots.html). Subject: GS012B Feedback Dear PI, We have examined the data for project GS012B on 16 Sep. 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 1641+399, 1946+7048,1819+6707,1600+7131,0513+7129. 4. Cross-correlation bandpass plots were generated for all baselines to HN for scans on 1641+399, 1946+7048,1819+6707,1600+7131,0513+7129. 5. Weather and Tsys plots for the VLBA antennas for your project will be sent with the data tape(s). NOTES: BR: okay HN: okay FD: dead track 9 (recorder problem at site) IF#4: RFI @ 12:42 KP: Tape in search 11:41 - 11:44. IF#4: RFI @ 12:42 LA: IF#4: RFI @ 12:42 MK: IF#4: RFI @ 12:42 NL: okay OV: IF#4: RFI @ 12:42 PT: IF#4: RFI @ 12:42 SC: IF#3: RFI @ 14:53 EB: IF#3: RFI @ 12:42 JV: Dead track 22 throughout project. IF#2 missing. (IF#4 gone at 14:56) RFI on #3 & 4. WB: RFI on IF 1. RFI on IF 3 at 17:07, 18:46. Big RFI spike at 18:56. Playback variable throughout project. Tape in search 10:00-11:20 and 17:40 - 18:40 TR: Playback variable. Bandpass edge problem or RFI on IFs 2 & 4. Subject: GW016 Feedback (missing) Dear PI, We have examined the data for project GW016 on 16 Sep. 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. 4. Cross-correlation bandpass plots were generated for all baselines to HN,EB for scans on All. 5. Weather and Tsys plots for the VLBA antennas for your project will be sent with the data tape(s). NOTES: Sniff of GW016: FD has low weights. There was a problem that has since been found and fixed with track 9. This was a formatter problem. It appears that the data may be ok for some of the time, probably some fraction of the barrel roll, since the weights drop to about 3/8, not 0. PT had a period of severe problems with the tape drive at the site causing loss of an hour or so of data. During observations, the operators switched to the other drive and the recording was fine afterwards. Part of a pass was lost after the switch, probably because the second tape did not start in an appropriate position for the schedule - an expected effect. MC had a large rate in the trial job. Jason will put in a rate and run a quick fringe search to check it out. Then we'll go into production. WB has poor playback - it is continuously in and out of sync. I'm trying to find out why. TR had poor playback, especially after the start. It was much worse in both the first "final" processing and in the reprocessing than during the trial or and other experiments GS012B and V041D. During the reprocessing, TR was moved to a different drive to try to improve playback. Problems were noted in tracks 2, 3, 23, and 27-33 - this looks like tape edge problems. JV was in search most of the time and the weights are poor when it was in sync. It turns out that the reason the correlator was in search is that the tape footages were off by over 9000 ft. According to the logs, the tape starts at about -9000 ft and all footages are off by about that amount. The correlator goes to the logged footage at the start of a job (there was a new job every 0.5 to 1 hour for this project) and looks for the data. If it finds it, it then determines a correction to use for other footages. But it will only spend a certain amount of time looking. For the first job, and, as luck would have it, the one we used for fringe searching and the trial run, the first scan is at the beginning of the tape. The log footage is high and negative, but the correlator cannot position before the start of tape, of course. Therefore, it starts at the beginning of tape and quickly finds the data it wants. However other jobs started in the middle with footage errors of up to 9000 ft. That was just too much and the job would not "prime". It would then just try to play from the logged footage and spend most or the whole job trying to catch up. We ended up reprocessing the experiment, after adding an appropriate number to all JV footages. On the recorrelation, the forward passes synced ok. The reverse passes has other problems as described in the next entry. Please - in the future - observing stations should reset the footage counter when a tape is loaded! JV has zero weights on the first two channels. Looking at the VT table, the problem is a dead track 22. With polarization on, when one channel of a stokes set has zero weight, all channels of the set are given zero weight. This means that in 1:4 fan out, 2 bit mode 16 track barrel roll (or any 4 track per channel, 8 track roll) observation, the barrel roll provides no protection. In fact, even worse, it wipes out a channel that would be ok in non-polarization processing. In addition to the track 22 problem, we got no good data on the reverse passes. This is because, in the reverse direction, all the high numbered tracks were blank which caused flagging to happen on all channels. Here are the gory details from George Peck: >From gpeck@zia.aoc.NRAO.EDU Thu Nov 13 15:06:40 1997 Date: Thu, 13 Nov 1997 15:06:35 -0700 (MST) From: George Peck To: pperley@zia.aoc.NRAO.EDU Cc: cwalker@zia.aoc.NRAO.EDU, gpeck@zia.aoc.NRAO.EDU Subject: Joddrel Bank Tape Peggy, I looked at the Joddrel Bank tape from GW016. The forward passes look good, with the exception of track 22 which is dead for the entire tape. The SNR is on the order of 21 and 22 dB, which is good enough. On reverse passes, tracks 2-21 and 23-26 look good. Track 27 still is quite good, but has some dropouts where the tape didn't seem to be in contact with the head. Track 27 does have some problems in GW016, as shown by the track statistic plots. Track 28 is very poor. The SNR is 13dB, and the signal level varies greatly with time, indicating that the tape was in poor contact with the head at all times. In the reverse direction, there is no power on the tape from tracks 29-33. It seems that there is a tape path problem which is causing that tape to be lifted from the headstack for the high numbered tracks in the reverse direction only. The high numbered tracks look good in the forward direction. -George For the record, ON was did not observe because of wind. There were no fringes at any time to GB. We have no idea why despite an extensive effort to find out. There has been at least one other mystery failure at Green Bank this year. I fear that there is something wrong in the system. VSOP observations both before and after GW016 had fringes at very similar frequencies. About the only significant difference that I can think of is the barrel roll. The VSOP projects have it off, GW016 had it on. In one of our tests, we turned off the barrel roll on playback at GB There were no signs of fringes. A VLBA site treated the same way had strange (low frequencies only), but obvious, fringes. We also did a zero baseline test and go good correlation of the pcal tones. Therefore there is no problem with LOs in the VLBA rack. However the pcal injection is in the back end so this doesn't test the first LO - but that was the same for successful project V041D immediately after GW016. Test observations will be run on Nov 18 to try to chase down the problem. KP had a bad track 20 for about an hour. I don't know if this was record or playback. NT started out with poor playback on the first correlation for somewhat less than an hour, then got better. There were a few bits of low weight data later. Mostly the playback for this stations was ok, but there were enough exceptions to suggest that the recording is not robust. On the reprocessing, it looks very good so we must have had a playback unit somewhat better matched to the recording. MC and EB look good, as do most of the VLBA stations and the VLA. LA has some big spikes about 06:03. RFI? But at same place in band at two frequencies. This persists while the antenna is low in the east (rising). It sounds like RFI from Tesuque peak or some such. The fringes are affected fairly seriously. Y has big ripples in the AC passbands. Is this the VLA IF bandshape? TR has DC spikes in the LCP autocorrelations. Also the AC amplitudes suggest large clipper offsets (big channel to channel variation. JV has larger spike at about 1673 MHz. This same spike (or close) appears at EB at around 10 UT. WB has very high fringe rates even to EB. We probably should get a better position for this station Subject: V041D Feedback Dear PI, We have examined the data for project V041D on 17 Sep. 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 '1928+738'. 4. Cross-correlation bandpass plots were generated for all baselines to EB for scans on '1928+738'. 5. Weather and Tsys plots for the VLBA antennas for your project will be sent with the data tape(s). NOTES: JV - Very poor recording, with IF 2 completely dead for almost all of the experiment. Fringes to EB in IF 1. TR - Recording was quite poor, and there is a fairly strong DC spike. Fringes to EB in both IFs. WB - Poor recording every other pass. Fringes in both IFs. IF 1 has an enormous spike at about 14 MHz. MC - Bad spike, probably due to interference, at about 6.5 MHz in IF 1. Strength varies, but always quite strong. Recording was good, and there are fringes to EB in both IFs. NT - Looks quite good. A couple short periods of slightly marginal recording. Fringes to EB in both IFs. EB - Looks quite good. Tape lost synch. for 10 minutes around 0602, but recording is otherwise quite good. GB - Good recording, good fringes. NZ - Recording is a bit ratty at times. Tracking station had problems at the start, and there are no HALCA fringes until about 1820. One small 80 nsec delay jump at about 2025, jumping back at about 2050. Rates got quite high, up to 250 mHz, at the end of the pass near 2130. The reason is a little unclear, since perigee was not until 2238. The change is smooth, so it's possible this was caused by a poor predicted orbit. GZ - Good recording quality. Residual delay around -0.9 microseconds. Two small delay jumps of about 50 nsec in size; one at about 2340, the other at about 0120. Large delay jump (to about -0.25 microsec) occurred around 0400, with no fringes around 0350-0400. UZ - Recording quality not great, but pretty good. No Time Correction File supplied, so residual rates are quite high and variable. Substantial coherence loss caused on short time scales. See memos on NRAO Space VLBI web site, at http://www.aoc.nrao.edu/space_vlbi/aoc/ioc/calreps.html, for further information. Note that because of a problem with the NZ log, there is some data for NZ that was correlated with a sky frequency of 1000 MHz. This is from a time before NZ successfully linked to the spacecraft, so there is no data loss. However, it can wreak havoc in AIPS. The solution, VERY IMPORTANT, is to run FITLD with SELFREQ = 1634 and SELBAND = 16000. (This selects the reference frequency of 1634 MHz and bandwidth of 16 MHz per iF.) This should eliminate all problems in AIPS that might be caused by the spurious second frequency. 6cm Global Session Subject: GC018A Feedback Dear PI, We have examined the data for project GC018A on 18 Sep. 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 J0004+461, J0717+454, and DA193. 4. Cross-correlation bandpass plots were generated for all baselines to HN for scans on J0004+461, J0717+454, and DA193. 5. Weather and Tsys plots for the VLBA antennas for your project will be sent with the data tape(s). NOTES: CM: Record or playback is poor. Track 22 is dead. RFI often present in IFs 3 and 4; maybe causing distorted passbands. IFs 3 and 4 are weak throughout the run. FD: Track 9 is dead. ON: RFI often present in IF 3. TR: Record or playback sometimes poor. WB: Record or playback sometimes poor. All other stations that observed: OK Subject: GL021B Feedback Dear PI, We have examined the data for project GL021B on 19 Sep. 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 1613+341, 3C286, 1308+326, 1539+277. 4. Cross-correlation bandpass plots were generated for all baselines to HN & TR for scans on 1613+341, 3C286, 1308+326, 1539+277. 5. Weather and Tsys plots for the VLBA antennas for your project will be sent with the data tape(s). NOTES: BR: okay FD: Dead track 9 (recorder problem at site) HN: okay KP: okay LA: okay MK: okay NL: okay OV: okay PT: okay SC: okay Y27: okay EB: okay CM: Dead track 22; other tracks very poor playback. IFs 1 & 2 dead. IFs 3 & 4: odd bandpass shape and spike in the middle (front end problem?). Lower half of each bandpass on IFs 3 & 4 has increasing phase wind, and upper half is just noise. NT: Dead track 23, 13:00-14:50. (IFs 1 & 2 dead during this time) TR: Tracks 2 & 3 poor, especially after ~17:00 WB: Head position errors frequent during playback. Pops in & out of sync a lot. All tracks dead for the first 50 minutes. IFs 1 & 2 dead for first 6 hours. MC: problems at site, 10:00-10:45 Most sources too weak to produce strong rates & delays. Wb observed cross polarized for gl021b. We did not discover this until the project had been fully correlated. Initially we were not going to re-correlate gl021b because Wb could be uncrossed with SWPOL in AIPS. However, the general lack of polarization state info in all MkIV logs prompted a re-correlation anyway. During this re-correlation Wb was uncrossed. Ergo, SWPOL will *not* be needed to uncross Wb in the FITLDed data. Subject: V022B Feedback Dear PI, We have examined the data for project V022B on 20 Sep. 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 0740+768. 4. Cross-correlation bandpass plots were generated for all baselines to EB for scans on 0740+768. 5. Weather and Tsys plots for the VLBA antennas for your project will be sent with the data tape(s). NOTES: Spacecraft fringes are pretty weak. For Gz, the fringes were detected for most of the pass using a 4-minute solution interval. The fringes were found at delay of about -1000 ns relative to Eb. For Tz, fringes were found in both passes; in the second pass (~1200 - 1350 UT) there appears to be a bimodal quality to the delay solution between -1000 and -1150 nanosec (relative to Eb). For Uz, data was recorded but no time correction file (tcf) was delivered to the correlator, and we couldn't find any fringes to the spacecraft when we tried correlating without the tcf. Weights showed that recording was very bad for most of the run at Cm, for most of the reverse tape passes at Nt, and for Tr after the first 1.5 hours. Also the reverse tape passes for Wb were marginal. There is no phase-cal at Tr or Wb. Channel 2 is apparently almost entirely dead at Cm, probably because of a dead track/head. Channel 1 has a very strange bandpass; the response is near zero at both ends, with a camel's hump in the middle. When channel 2 shows up, it also has a peculiar bandpass, ramping up to a maximum at about 12 MHz, and then falling precipitously. Eb has a DC spike in the autocorrelation spectrum. Tz has an intermittent DC spike in autocorrelation. Gb has far too much power in the phase cal, mostly in IF 2. This may affect the SNR. Wb and Cm have no obvious fringes most of the time in the sniffer. On shows no fringes in IF 2, although the recording looks okay and the autocorrelation spectrum of IF 2 looks ok as well. Ud did not supply a clock file; they have fringes at a residual delay of -4900 nanosec relative to Eb. Subject: GP015C Feedback Dear PI, We have examined the data for project GP015C on 20 Sep. 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 HN 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: BR: okay FD: poor track #9; recorder problem at site HN: okay KP: okay LA: okay MK: okay NL: okay OV: okay PT: okay SC: tape in search from 21:45-22:35, 23:30-00:20, 01:10-01:50 EB: okay CM: Dead track 22. Poor tracks 32-33. Bandpass edge problems or RFI in IFs 1 & 2. IF 3 dead. Non-linear phases or weak fringes for most other IFs. (complex bandpass calibration may be required) MC: okay NT: okay WB: weak fringes throughout observation (low amplitudes) ON: Dead tracks 15-21 from 21:50 to 22:35 Possible RFI in IF 5 TR: poor tracks 2,3,27-32 throughout run Y1: okay Subject: GM030 Feedback Dear PI, We have examined the data for project GM030 on 21 Sep. 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 1803+784, 2007+777 and 0917+624. 4. Cross-correlation bandpass plots were generated for all baselines to HN for scans on 1803+784, 2007+777 and 0917+624. 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: dead track #9 (known receiver problem at site) PT: OK LA: OK KP: OK OV: OK MK: OK BR: OK Y: CH 1 bandpass edge problem, CH 7&8 out of range of VLA bandpass filter No fringes on CH 7&8. Lightning storm affected phasing of the array. EB: Good fringes on all fringe finders. NT: CH 1,2&7 slightly odd bandpass shapes. Good fringes on all fringe finders. Subject: GP015D Feedback Dear PI, We have examined the data for project GP015D on 21 Sep. 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 srcs. 4. Cross-correlation bandpass plots were generated for all baselines to EB 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: BR: okay FD: dead track 9 (recorder problem at site) HN: okay KP: okay LA: okay MK: intermittently searching for the first hour NL: okay OV: okay PT: okay SC: okay Y: okay EB: okay WB: Tape intermittently in search. We reversed the even & odd IF tracks to "uncross" the polarization at WB. Result: good, strong fringes CM: CM: track 22 bad. Strange bandpass shape; possible RFI or bandpass edge problem in IFs 1 & 2. ON: fringes seen only on even channels MC: Tape in search, 18:30-18:42, 20:02-20:22. Dead track 5 at 23:07. TR: Weak tracks 2-4, 20:00-23:30. NT: good playback Subject: V347A Feedback Dear PI, We have examined the data for project V347A on 22 Sep. 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 . 4. Cross-correlation bandpass plots were generated for all baselines to EB for scans on . 5. Weather and Tsys plots for the VLBA antennas for your project will be sent with the data tape(s). NOTES: Cm 2nd IF out most of the time. 1st IF has a strange bandpass shape. Very poor recording (because of 2nd IF) Eb DC spike in autocorrelation Mc looks good Nt poor recording On 2nd IF never fringes even though autocorrelation looks fine. Does not fringe at all from 4:00-4:17. Tr poor recording; had pointing problems which caused a loss of signal in approximately 15 minute intervals starting at 5:43, 6:33, 7:09, 7:43 and 8:18. Wb Failure do to crossed polarizations. Halca: Gz fringes over whole pass, weak near apogee Tz fringes over whole pass Rz fringes in last 2 hours of the pass Uz no fringes detected in fringe searches, not correlated (For plots of delay, rate and SNR for these passes see the NRAO Space VLBI webpage) Subject: V085I Feedback Dear PI, We have examined the data for project V085I on 23 Sep. 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 '0636+680'. 4. Cross-correlation bandpass plots were generated for all baselines to EB for scans on '0636+680'. 5. Weather and Tsys plots for the VLBA antennas for your project will be sent with the data tape(s). NOTES: Spacecraft fringes are very weak. For GZ, they are usually there between 0200 and 0315, with 5-minute solution interval. For TZ, they are there only about half the time between 0830 and 1115, using the same solution interval. GZ delay jumps from -1.125 microsec (relative to EB0 before 0220 to -0.975 microsec after. TZ delay is steady at -1.2 microsec. RTS NOTE: GZ TRACKED VSOP ONLY BETWEEN 0200 AND 0315, AND TZ ONLY BETWEEN 0830 AND 1115, A TOTAL OF FOUR HOURS Two tracking stations failed. RZ is known to have failed completely. UZ apparently tracked, but did not deliver a Time Correction File, and no fringes were found without it. Weights showed that recording was terrible at CM and NT, marginal at TR. There was 10 minutes of bad recording at the beginning of the observing in GB, then the weights were okay after that. There is no phase-cal at TR or WB. Channel 2 is apparently almost entirely dead at CM, probably because of a dead track/head. However, AIPS shows that there are some fringes at 0840 with CM, so a little bit of the data may be salvageable. Channel 1 has a very strange bandpass; the response is near zero at both ends, with a camel's hump in the middle. EB has a DC spike in the autocorrelation spectrum. TZ has an intermittent DC spike in autocorrelation. GB has far too much power in the phase cal, mostly in IF 2. This may affect the SNR. WB has no obvious fringes most of the time in the sniffer, although there are some signs of an occasional weak fringe. NT has no fringes until 0620, but looks okay after that (except for marginal recording). ON shows no fringes in IF 2, although the recording looks okay and the autocorrelation spectrum of IF 2 looks good. UD did not supply a clock file; they have fringes at a residual delay of -4.4 microsec relative to EB. UD appears rather insensitive for a 64m antenna, with the SNR on its fringes less than for GB or MC. MC is the only station which has no problems to write about. Subject: GV015 Feedback Dear PI, We have examined the data for project GV015 on 23 Sep. 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 FD 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: CM: Dead track 22, weak tracks 23 and 25. Channels 3 and 4 either look dead or have strange bandpass shapes with possible RFI (or maybe a frontend problem). MC: In search from ~16:00-17:00. NT: Weak on all tracks, popping in and out of sync. TR: Playback weak on tracks 28-32 even. WB: Poor playback on tracks 26-33. Channels 3 and 4 intermittently look dead. ON: Possible weak RFI spike in channel 3. No fringes on odd channels. EB: OK VLBA HN: OK NL: OK LA: OK PT: OK KP: OK OV: OK BR: OK MK: OK SC: Not used. Bad focus motor. VLA: Dead track 12 from ~16:00-16:10 Comments: EB was also used as a sniffer ref. ant. When used the delays changed discontinuously between EB and the VLBA stations in the delay plots. Subject: GC018B Feedback Dear PI, We have examined the data for project GC018B on 24 Sep. 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 4C39.25, J0004+461, and J0217+454. 4. Cross-correlation bandpass plots were generated for all baselines to HN for scans on 4C39.25, J0004+461, and J0217+454. 5. Weather and Tsys plots for the VLBA antennas for your project will be sent with the data tape(s). NOTES: VLBA SC: Did not observe due to a focus motor fault. HN: OK NL: OK FD: OK LA: OK PT: OK KP: OK OV: OK BR: OK MK: OK Other VLBI stations CM: IF channel 3 is missing due to dead track 22. There is RFI in IF channel 4. ON: There is RFI in IF channel 3. EB: OK WB: In search 13:30-13:50 NT: OK TR: OK MC: OK Subject: V022C Feedback Dear PI, We have examined the data for project V022C on 25 Sep. 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 1809+568. 4. Cross-correlation bandpass plots were generated for all baselines to EB for scans on 1809+568. 5. Weather and Tsys plots for the VLBA antennas for your project will be sent with the data tape(s). NOTES: Spacecraft fringes are fairly weak for this source also, although stronger than for the source in V022B. For the three DSN tracking stations (Gz, Tz, and Rz) the fringes are still found at a delay of about -1000 ns relative to Eb. There are some delay jumps or "glitches" for all three of these stations; the size of these delay jumps are 100 - 200 ns. Fringes were detected for all three stations, but the first pass at Rz (~0845 - 0915 UT), we did not detect fringes from Eb to the spacecraft. The fringes were somewhat stronger during the Nz pass (~1440 - 1830 UT) although they seem to go away during the last half-hour. There is a gap from about 1605 to 1625 UT where the fringes also go away. After this gap the residual delay at Nz also has a "jump" of about 40 ns or so. For the Uz pass (~0915 - 1230 UT), data was recorded but no time correction file (tcf) was delivered to the correlator. We believe we detected very weak fringes to the spacecraft using the Uz tracking station from about 1015 to 1230 UT when we correlated without the tcf but we suspect that the data will not be very useful. Weights showed that recording was very bad for most of the run at Cm. The recording is better but still rather poor for Nt and Tr. Despite the recording problems at Cm, there are still fringes from Eb to Cm. There is no phase-cal at Tr or Wb. The bandpass for Tr from the first IF looks somewhat atypical; there is a fairly broad "hump" at about 12.5 MHz, and on the high frequency end it falls precipitously. Channel 2 is apparently almost entirely dead at Cm, probably because of a dead track/head. Channel 1 has a very strange bandpass; the response is near zero at both ends, with a camel's hump in the middle. When channel 2 shows up, it also has a peculiar bandpass, ramping up to a maximum at about 12 MHz, and then falling precipitously. Eb has a DC spike in the autocorrelation spectrum. Tz has an intermittent DC spike in autocorrelation. Gb has far too much power at times in the phase cal, mostly in IF 2. At other times the phase cals look fine, and we saw at least one short time range (~1706 UT) where the phase cals seem to have gone away completely. The phase cals at Nt also may be stronger than one would expect (especially in IF 1). On shows no fringes in IF 2, although the recording looks okay and the autocorrelation spectrum of IF 2 looks ok as well. Ud did not supply a clock file; they have fringes at a residual delay of -4600 nanosec relative to Eb. There is an intermittent DC spike in the autocorrelation spectrum at Ud and there may also be an intermittent spike at the high end of the bandpass. No clear problems were found for MC. X-band Session ---------------- Subject: GG032A Feedback Dear PI, We have examined the data for project GG032A on 26 Sep. 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 3C345, OQ208, & 3C279. 4. Cross-correlation bandpass plots were generated for all baselines to NL & EB for scans on 3C345, OQ208, & 3C279. 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: Missed first 9 minutes; see obs. log KP: okay LA: okay MK: Missed first 4 minutes; see obs. log NL: okay OV: okay PT: okay SC: okay Y1: okay EB: okay MC: Poor playback on tracks 17, 23-26,28,29 from 14:00 - 17:00. RFI on IFs 1,3,5,7 from 14:00 - ~22:00 RFI on IFs 1-4, ~22:00-23:15 NT: Tape popped out of sync intermittently, especially 14:00 - 14:45 and 15:30 - 16:15 (first 2 forward passes) Sometimes, fringes on IFs 1,3,5,7 are considerably stronger than fringes on IFs 2,4,6,8. ON: okay WB: Occasionally pops out of sync briefly on reverse passes. YB: Dropped from correlation; formatter errors preventing us from finding any fringes. Subject: GG032B Feedback Dear PI, We have examined the data for project GG032B on 27 Sep. 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 4C39.25, 3C279, OQ208. 4. Cross-correlation bandpass plots were generated for all baselines to HN & EB for scans on 4C39.25, 3C279, OQ208. 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: okay KP: okay LA: okay MK: okay NL: weak on tracks 26 & 28 from 12:00 - 15:00 OV: okay PT: RFI in IFs 1 & 2 at ~13:41 SC: okay Y1: RFI, IF 8, at 15:42 EB: Computer problems at site from 08:00 - 09:35 MC: dead track 5, 08:10-08:20. dead tracks 24-25 from 12:55-13:05 & 13:35-14:05 IFs 3 & 4 dead at ~13:41 due to above. NT: Weak tracks 2-3 from 08:00 to 08:45. Pops in & out of sync from 17:20 - 18:00 Fringes in odd IFs only ON: Fringes are very weak in all channels WB: Fringes only in even IFs YB: dropped from correlation; formattor errors; couldn't find fringes Subject: GP016 Feedback Dear PI, We have examined the data for project GP016 on 27 Sep. 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 0646+600,1242+410,1843+356,3C84. 4. Cross-correlation bandpass plots were generated for all baselines to HN & EB for scans on 0646+600,1242+410,1843+356,3C84. 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: okay KP: okay LA: 16:20-16:30: every fourth track dead MK: okay NL: okay OV: okay PT: minor RFI in IF 1 SC: okay Y1: okay EB: Tape slow to sync at the beginning. Tracks 21-32 dead from 23:00-23:30 MC: Amplitude of IF 3 is lower than other IFs NT: Slightly variable weights for first 13 hours ON: First tape (covering 22:30 - 10:57) was damaged and unusable; all data for first half on project lost. Tracks 12-13 poor from 12:20-13:00. YB: Dropped from correlation. Continuous formatter errors prevented us from finding any fringes