With the search for returned IMC ideal, we've reported that the SEI system puts the platforms back from whence they came (before the vent.)  Rather than just relying on our position control loops to do that, the controlled cartesian dofs and the local positional sensors were trended from before through the present after returning to pumped down condition.  This was done for both HAMs 2 & 3.

This showed that in fact the control loops are doing exactly their job--the six cartesian dofs for the HEPI and ISI platforms for both HAMs 2 & 3 have returned to the pre-vent position.  No errant reference position has corrupted the location.  Looking at the local sensors, on the ISIs with just six sensors for the 6 dofs (X Y Z RX RY & RZ), these sensors too have returned to exactly the pre-vent position.  On the HEPIs with an over-constraining 8 sensors for the six dofs, the local sensors do show small local positional shifts.  During the vent, the horizontal sensors clearly show the distortions the vacuum system but the cartesian positions while they see the disrupting air motion, remain locked in place.  Since the pringle modes of the HEPI have been removed from the locked positional control, the local sensors do lock onto a more repeated position to hold the cartesian position.  The vertical sensors of HEPI show even less shift after the vent than the horizontals.  Generally, all the local sensors on HEPI are within about 100 counts of their pre-vent count.  At 655cts/mil:  100cts = 0.000153"=3.9um.

HEPI and ISI for HAMs 2 & 3 are good.