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.