Temperature sensors for the HVAC system tend to be on the walls. So when it is really cold outside, I think the temperature at the chambers tends to be higher than usual because the system is trying to maintain temperature near the walls, which, because of the higher gradient, tend to be colder relative to the room than usual. Figures 1 and 2 show a moderately good correlation between range/inability to lock and BSC3 temperature (BSC1 is not that different). The trouble really seems to start when BSC3 warms up above 9810 counts. It seems like a long shot, but it might be worth turning the zone 1A temperature set point down, and perhaps others as well, when it is cold, so that the temperature is not so hot away from the walls. Figure 3 shows that BSC3 tends to be warm when the outside temperature is cold. Eventually it might be good to control the HVAC with sensors near the chambers and not on the walls.
Indeed, it does look like the temp of the LVEA has been wandering more the last few days than it was last week when we at least had ~60MPC locking and is seen by vertical drifts in the ITM and BS suspension which are translating to pitch motion (see attached). Not sure if this is the only culprit for why we're down on our lock acquistion, but plots attached are complement to Robert's plots.
IMs don't look too far off from where they were during last 8Mpc locks... IM4 is a few clicks off but people have been doing various adjustments of it during alignments over the last few days.
End station temps look to have stabilized over the last ~10 days, although the ETMy and TMSY have been drifting in vertical since then for some reason, maybe following other pointing issues around.
FYI. We have seen similar behaviour of QUADs at LLO during a recent cold snap, vertical heights drifted by as much as -50 um, approaching close to -100 um, which is our threshold where we begin to get concerned about bottoming out on earthquake stops. The sagging is indicative of heating of the blades, despite the cold weather and stability exhibited by the HVAC system maintaining VEA set-point temperatures, therefore, I suspect additional HVAC heating could be responsible for the drift observed in the suspensions (see LLO aLOG entry 30776).
