Today we had a brief period of time where the 28 Hz line was very large. Looking at the DARM spectrum, it seems to be at 28.22 Hz. Note that this is then different from what was observed last Friday, where it was 27.5 Hz, but it is at the same frequency reported by Georgia. Looking at a list of bounce mode frequencies this is consistent with PR3 mode.
The spectrogram below shows that something started at about 40 Hz and slowly and very linearly ramped down to 26 Hz in about 100 seconds, then stayed constant at that frequency for about 100 more seconds, before turning off.
All accelerometers and all microphones in the LVEA see the sweeping noise.
Note that the problem in DARM is not only the 28.2 Hz bounce mode being rang up: during the time this noise is sweeping, it is very well visible in DARM too.
The HAM1 accelerometer sees the largest signal. Also, when the noise turns on, the initial "burst" is 0.1s earlier in the HAM1 accelerometer than in the CRYO accelerometers.
