Rana pointed out to me that the PR3 and SR3 suspensions may still have some shift due to wire heating during locks (which we won't see until a lockloss, since we control the angles of mirrors during lock).
Attached are the oplev signals for PR3 and SR3 at the end of a few different lock stretches, labeled by the time of the end of the lock. The lock ending 3 Aug was 14+ hours. The lock ending 31 July was 10+ hours. The lock ending 23 July was 5+ hours. The lock ending 20 July was 6+ hours.
The PR3 shift is more significant than the SR3 shift, but that shouldn't be too surprising, since there is more power in the PRC than the SRC so there is going to be more scattered light around PR3. Also, PR3 has some ASC feedback to keep the pointing. SR3 does not have ASC feedback, but it does have a DC-coupled optical lever. SR3 shifts usually a few tenths of a microradian, but PR3 is often one or more microradians. Interestingly, the PR3 shift is larger for medium length locks (1 or 1.5 urad) than for very long locks (0.3 urad). I'm not at all sure why this is.
This is not the end of the world for us right now, since we won't be increasing the laser power for O1, however we expect that this drift will increase as we increase the laser power, so we may need to consider adding even more baffling to the recycling cavity folding mirrors during some future vent.
Note - The PR3 and SR3 have 2 different baffles in front of them which do different things. The PR3 HAS a baffle which specifically shields the wires from the beam. The SR3 does not have this particular baffle, however I believe we ave a spare which we could mount at some point if deemed necessary.
Attached is a picture of the PR3 "wire shielding baffle D1300957, showing how it shields the suspension wires at th PR3 optic stage. In fact, a picture of this baffle was taken from the controlroom and is in alog 8941.
The second attachment is a repost of the SR3 baffle picture from alog 16512.
from the pictures, it seems like we could get most of the rest of the baffling we need if the wire going under neath the barrel of PR3 were to be covered. Perhaps that's what accounts for the residual heating. Also, if it became a problem perhaps we can get an SR3 baffle with a slightly smaller hole to cover its wires.