A large peak at 54 Hz has appeared in DARM; it was not large the morning of Wed June 6th or anytime before, shows up fully on Thursday and has remained since. (We locked very briefly Wed and the peak can be seen but is not very high). It seems due to some change occuring on Wednesday. There was a new chiller turned on Tuesday for a test, but was turned back off as evidenced by the accelerometer close by. There was cabling change of PD for IMC. I have looked through most accelerometer, seis, and mic channels and do not see evidence of anything mechanical turned on during this time.
The coupling of 54 Hz changes, but when it is elevated it shows clear correlation with the top of the hour. I show 50.5 - 55 Hz DARM over longer time and shorter (to see exact hour jumps), compared with another band in DARM to show it's just this peak. Again, I've compared time correlation with all ENV seis, mic, and acc and find nothing. We could use some help from DetChar on this, running slow correlation or looking through temperature control (air conditioner, etc) channels, etc.
Bas noticed that the 54Hz non stationary behavior is correlated with lines of the forest (Figure 1). Also we observe that the 54Hz line is seen (but poorly coherent) in PRCL and MICH (figure 2).
To test the hypothesis that this line is linked with the timing, this morning we used a fan blowing onto the GPS receiver board to temporarely cool it down. We run the fan from 8:11 to 8:18 UTC.
This was very effecting in moving all the forest (Figure 3).
We see there is some residual of timing lines in hrec which survive the subtraction, particulrly the 380Hz (Figure 4).
During the thermal transient we can see the 54 Hz line changing its amplitude while a bunch of 1-Hz spaced lines crossed it as if this 54Hz line is beating with the timing lines (Figure 5).
Bas noticed that the 54Hz not stationary behavior is correlated with lines of the forest (Figure 1). Also we observe that the 54Hz line is seen (but poorly coherent) in PRCL and MICH (Figure 2).
To test the hypothesis that this line is linked with the timing, this morning we used a fan blowing onto the GPS receiver board to temporarely cool it down. We run the fan from 8:11 to 8:18 UTC.
This was very effective in moving the whole forest (Figure 3).
There is some residual of timing lines in hrec which survive the subtraction, particulrly around 380Hz (Figure 4).
During the thermal transient we can see the 54 Hz line changing its amplitude while a bunch of 1-Hz spaced lines crossed it, as if the 54Hz line is beating with the timing lines (Figure 5).