Yesterday, the masses on the STS2s were centered but I should have monitored the mass positions more in real time as the centering doesn't always take the first or second time around. While we did improve things maybe, there are still problems: six of the nine masses (3 masses 3 sts2s) were out of spec but after centering, there are still 3 of the 9 out of spec.
At EndX, the STS2 had two masses out of spec by about 50% (7500 cts vs 5000); after centering one of those came into spec but the other overshot and is now out by a factor of 5! Attached is ASDs of before and after. The refs are from 2am Tuesday and the currents are from 2am this morning. The useism is likely a bit higher early this morning (not as high as it is right now though.) There is not anything glaringly wrong to me here. In general the current traces are higher than the references but again that could just be the actual ground motion. I thought such a large mass position problem would be obvious but it is not to me. I'll do a comparison of LVEA instruments at the same time.
Here are two day trends of the three corner station STS2 Mass positions. The bottom row are the U mass, middle are Vs and the top are W masses. The first column, B2 is the STS2-B (itmy,) the middle column is the B1, STS2-A located near HAM2, and the third column, B3 is the STS2-C near HAM5.
Currently, STS2-B is the unit used for all the corner station sensor corrections. Yesterday's centering step is clearly visible and please note that the U mass shifted alot but is still equally out of position. B1, the HAM2 unit is not in service and was not centered yesterday. I do not understand why there is a glitch to zero at the time. We did connect a DVM to the Pos Spigots...maybe we toggled the UVW/XYZ switch and that is the glitch. The third column shows the HAM5 B3 unit which we did center although it looks like we really did not need to do that. Please note the various noise levels on these channels and especially how that changed on the B3 V signal, whats up with that?
Here is the spectra comparison at ETMY where the zeroing seems to have improved all the mass positions although one still is out of spec by maybe 50%. SImilar story to the EndX assessment above: nothing obvious given the potentially different ground motion. However, if you compare the ENDX and ENDY spectra, it sure would appear that the ENDY sees much more tilt than ENDX.
Here is the promised same time comparison after centering for the STS-B and C units. Again, the centering on the C unit was probably not needed (we were testing the process) and the centering on the B unit just sent it to the other side of zero with no real improvement in position.
Couple thing from this. See how the traces are almost exactly the same from .1 to 6 hz on the Y dof? That suggests these two instruments are doing well in that channel. Below about 60mHz, tilt starts to get in the way here; above 6 hz, wavelengths bring about differences. On the X and Z axes, the difference in this region between the spectra suggests a problem in those dofs. We suspect STS2-B, the ITMY unit. Now this could be because of the poor centering or maybe the difficulty in centering is a common symptom of the underlying instrument problem.
