Last Friday, the STS2-A near HAM2 had its igloo installed. The masses still look well centered. Attached is a view of the three LVEA instruments' ASD and coherence with each other. The thin current traces are from 0100utc when wind and seismic was minimal; the thick reference traces are from a week ago.
The improved thermal state of the HAM2 unit is evident on the Z dof where all sensors follow each other well and the coherence is much improved especially below 40mHz.
However, HAM2's Y & X performance at low frequency but especially the Y dof, show that HAM2 continues to have a problem even though Quanterra had the machine in their vault for a month and could not determine an issue. Since the Z signal is determined from all 3 masses, it suggests the problem might be in electronics converting U V W to Y and X.
The Z coherence plot suggests the HAM2 and HAM5 Z dofs are doing well but ITMY Z dof is flakey. The Y coherence indicates the HAM5 and ITMY Y dofs are okay but the HAM2 Y is not. The X coherence suggests the HAM2 is better than the ITMY as ITMY has worse coherence with both HAM2 & 5.
So summary:
The HAM2 unit, STS2-A does not work well in Y and is marginally better in X; it is good in Z.
The ITMY unit, STS2-B, does not work well in Z or X but is tolerable in Y.
The STS2-C, HAM5 unit works best even though we have to surmise X since both other units are poor in that dof. Jim would agree based on detchar and sensor correction performance.
Attached now is a comparison to above current traces, low wind, and, 1300utc when the wind was up to 20-30mph.
These results does not counter the conclusions above. The coherence amplitudes tend to be lower except for HAM5 to ITMY where they are actually much better. This maybe makes sense given they instruments are 1 m apart and Y is good or tolerable on those sensors. The wind tilt shows strong in HAM2 Y & X but is still evident for ITMY & HAM5. So maybe we could still look for a better placement in the LVEA at which to hide from the wind. I'd suggest moving -Y.
