Attached is a strain noise spectrum comparing the sub-100 Hz performance of H1 and L1 (inspired by a similar plot that Elenna made). The data was taken in the recent 5-hr long coincident lock, so H1 has its improved low-frequency noise that came from reducing the input power to 60 W. The L1 noise is lower by a factor of 2-3 in the 15-30 Hz band, and the H1 noise is lower below about 13 Hz.
Also noteworthy are broad noise peaks (as might be produced by scattered light) in H1 at 26 Hz, 39 Hz, and 52 Hz -- i.e., these peaks are separated by 13 Hz, though there's not a noticeable peak at 13 Hz.
I ran a fine resolution to see if I could find a corresponding 13 Hz peak to match the others in series. There appears to be something at 13.07 Hz, see attachment.
Some of the peaks in the series from 13.75-14.4 Hz are roll modes. Searching back through some alogs, the catalogued roll modes are as follows: ITMY 13.85 Hz, ITMX 13.9 Hz, ETMY 13.84 Hz, ETMX 13.77 Hz (see 43728, 57668). Not sure what the rest are.
