As a follow up to Betsy's log last night, I went out to ITMX this morning to release HEPI and look at actuator gaps. Payload is almost back to full, so I would expect if everything is healthy for HEPI to be pretty much centered. This is what I found, BUT... the vertical stops were all loose, meaning the platform had moved up some. I've also looked at IPS trends and they don't look horrible, reasonable shifts considering I locked with the loops on, a lot of payload came off then back on and we are still light some payload.So, a couple thoughts on what could have happened.

- Basically nothing. The error Jason found is all somehow in SUS. Seems unlikely.

- Some incredibly lucky/unlucky combination of horrible shifts. SUS removed a lot of payload, then pushed up on the platform a lot when they added back. I didn't get a really hard lock on HEPI because I was trying to preserve the aligned position, and it's really hard to reach all of the stops necessary. This means the platform could have moved up, moved the actuators in their mounts (if SUS pushed REALLY hard, seems unlikely) and somehow we have come back down just the right amount for HEPI to look more or less ok. I would expect that if we had come up enough to move the actuators 6mm (presumably when we removed payload or when SUS pushed on the platform with their arm), the platform would come back down and the HEPI actuators would be bottomed out. That's not what I found, so I don't know what's happening here.

Anyway, if Jason finds we are still 3 mm high, it means completely re-doing HEPI at that chamber. We should also re-check the level of the ISI at this point. Will probably also require re-doing some tests on HEPI, that we wouldn't otherwise do.