J. Kissel, O. Patane, F. Clara
ECR E2400330

Calling this out explicitly: 
    We have changed the OSEM PD satellite amplifiers on H1SUSPRM, H1SUSPR3, H1SUSBS, H1SUSSR3, and H1SUSSRM top masses; see LHO:85463
    We chose to implement ECR E2400330 by modifying spare chassis ahead of time, and installing those modified spares in place of the old chassis (which will become some other suspensions' "new" amps next week).
    Though the ECR only changes the whitening stage frequency response.
    However, because the old vs. new chasses have different set of other overall transimpedance gain determining components, the read-back for the OSEM PDs will likely change slightly.
    Thus, the OSEMs' recast as EULER basis signals will also change slightly, *looking* like an alignment change, even though the alignment of the physical suspension will NOT have changed.
    This won't be in any consistent direction, and the transimpedance gain is determined by components that have value at any value within the components' tolerance.

I attach two examples, H1SUSPR3 and H1SUSBS, of the levels we're talking about -- In the OSEM basis, it's 1-3 [urad], and same in the EULER basis. For the beam splitter, a physical change in alignment of that magnitude would be significant, hence me bringing it up explicitly.

So, the new normal for the following suspension alignment starts on 2025-07-01 12:30 UTC:
    H1SUSPRM
    H1SUSPR3
    H1SUSBS
    H1SUSSR3
    H1SUSSRM
We'll definitely have to re-run initial alignment after today's maintenance day, given that (unrelated)
    - we rebooted the entire electronics racks at EY to replace failing power supplies,
    - we rebooted the seih23
    - we adjusted the green camera alignment