A line that used to be around 85 Hz (since June at least) recently evolved in a peculiar way: Figure 1
during the night of Dec 2nd it slowly drifted to 88hz: Figure 2
during the lock of tonight it started moving significantly in frequency: Figure 3
Using the NonNA line tracker tool (still under development) I extracted the time serie corresponding to the frequency of the 88 Hz wondering line (see spectrogram attached). Then, using NonNA_corre, I cross correlated it with large sets of auxiliary channels finding it correlated in particulare with some accelerometers *_BS_*_ACC_* and *_SR_*_ACC_* channels. A plot showing the 12 most correlated channel is attached. Also, in the text file there is a larger list of channels and their Pearson's correlation coefficient.
Further investigation, making use of larger/different periods and different aux channels subsets, will be carried out soon.
The wandering line that used to be at 85 Hz, which started moving at around 88 Hz since Dec 5, from Dec 6 seems to be disappeared or jumped to about 97 Hz but fainter; see the spectrogram attached. It is inpossible to ensure that this is the same line as before due to the lack of continuity of the data during the unlock. In the next lockings of Dec 7 it became even fainter and it was impossible to track it any more. The origin of this line is still under investigation with NonNA tools and with hardware tests.
