2019 May

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May 09

11:03 UT The data from 19:00 UT yesterday until now are no good. Yesterday Kjell replaced the 800 MHz clock derived from the signal generator with one from a new Valon 5009 Synthesizer. Although the data seemed to be okay, I could not see any coherence in the phasecals or refcals. That prevented me from getting a delay correction. This morning I checked the delay using a communication satellite and discovered that two antennas, 8 and 14, had extremely high delays, about 300 ns! I rebooted the correlator this morning and rechecked, and now they are fine. I have seen this strange behavior once before, so I can only surmise that occasionally on a reboot of the correlator we can get really wacky delays on some digitizers (or ROACH channels--maybe not the digitizer itself). This suggests that we really need to make a quick observation of a satellite after a reboot in order to do a sanity check on the delays.

May 10

12:56 UT The delays have been updated this morning prior to today's calibrations. For some reason, ant13 has poor (but not zero) phase coherence as of mid-day yesterday. I just tried stowing to be sure it was not off in motor counts, but the stow looked nominal. I see no other indications of a problem.

15:14 UT I reset all of the gains just prior to the first calibrator scan, since I was not happy with the levels. Based on an earlier snapshot of a geosat, it looks like Ant13 receiver is not working at all, but I will try it again in a half hour or so to see if setting the levels helps.

May 14

22:00 UT Kjell was converting the new synthesizer for the correlator clock to its permanent location in the rack today, but ran into a lot of problems. Eventually he got it installed and working, so I had to reboot the correlator as a result.

May 15

02:40 UT The delays were reset after the correlator reboot.

12:02 UT It is getting frustrating that the Ant A control system dies each night around 2:00 UT. I have been trying to do an overnight calibration (X-Y delay phase calibration) and for the past two nights it died each time. The symptom is that the control system shows occasional 1-s outages most of the day, and then suddenly starts doing it a lot more (for a couple of hours) before it just stops. To combat this, I am trying to restart it every four hours (at 1, 5, 9, 13, 17, and 21 h), so we will see if this helps. Meanwhile, I could not even check the delays after the above reset because the Ant A receiver was not in the correct state for subsequent observations. Hopefully the first calibrator scan of today will be good.

May 19

15:02 UT Oh oh. I have been taking SKYCALTEST scans for about a year, and today I find out that they are not being done correctly! They were supposed to be taken as for a solar scan, but on the position of a calibrator. What I learned today is that while I did change the frequency sequence, it was done "manually" so that the setting of the DCM attenuation was not correct for the solar sequence. Instead, it was switching the DCM attenuation for the pcal_hi sequence. I am now doing a test that should result in a correct SKYCALTEST scan.