As a simple check I have used 30min of data starting from Aug 03 2018 03:23:20 UTC to make spectra of SDB2_B1p_PD1_Blended, for [0 10] minutes [10 20] minutes, [20 30] minutes.
Figure 1, 2 and 3 show the 4 arm mirrors drum modes, they drift up in frequency by a few mHz over 30 minutes. Hopefully this can be used by the line tracker to study the mirrors temperature during the first 10 minutes of dark fringe before the two OMCs lock.
