- 21:00 UTC, start of the shift, ITF in Science mode;
- 21:10 UTC (plot1) unlock after 2h37m;
- 21:50 UTC Science mode;
- 0:42 UTC (plot2) unlock after 2h51m;
- 1:17 UTC UTC Science mode;
- 2:36 UTC (plot3) unlock after 1h18m;
- 3:05 UTC WE LC open by the guardian after an unlock in LOCKING_DC_READOUT
- 3:47 UTC Science mode;
- 4:38 UTC (plot4) unlock after 50m
- end of the shift relock in progress ...
To be noted that since yesterday afternoon at 16:00 UTC there is the the following pathological situation: increase of SSFS_Correction and arising of the line at 273Hz in Hec, increase of the oscillation of the IMC reflection; see plot 5.
This kind of situation has been reported the first time Wednesday 12 June 2019 and it appears from time to time.
Suspensions
at 3:05 UTC WE LC were open by the guardian after an unlock in LOCKING_DC_READOUT; I was able to close the loop without major problems.
Software
TelescreenLeft and TelescreenRight restarted at 21:30 UTC because the images were frozen.
Guard tours (time in UTC)
from 22:20 to 22:50
from 0:50 to 1:20
from 2:40 to 3:10
from 4:15 to 4:45
A possible explanation of SSFS instability at 274.8 Hz is the presence of a spurious crossing between the mechanical loop on MC mirror (low frequency) and the loop on the laser frequency (high frequency), perhaps due to a high Q resonance of MC payload. This morning a narrow notch to MC loop has been added. Let's see if it works.
The instability seems back, but at a different frequency: 263Hz. this happens after yesterday maintenance, actually since the lock of 13:30 UTC (Figure 1)
The line is very strong in SSFS but also PMC TRA (Figure 2): where there are extra lines starting from 12.7Hz
A notch at 262.6 Hz has been added to SSFS_MC loop.