J. Kissel

I've aligned the GND T240 to the global IFO coordinate system (see LHO aLOG 12930 for discovery of mis-alignment). Further, in preparation for the UWash tiltmeter install, I've returned the PEM Guralp floor seismometer to inside the stubs of the PEM stay-clear zone.

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Details

Alignment / Leveling:
PEM's Guralp - The instrument doesn't have any holes for an alignment rod, so I had to align the instrument by eye. I've pointed the "North" direction (alignment nub near the the bottom of the instrument) in the IFO's +X direction (as it was already, in its previous location). I've also re-leveled the instrument, and re-covered it in its thermal shield. See first three pages of attached pictures. 
GND T240 - I used a brand new alignment rod "swizzle stick" (thanks Hugh!) to align the "North" direction in the IFO's +Y direction. See pgs 6-8 of attached pictures. (Hugh gave me a borehole micrometer with rounded tips to better measure the inner-diameter of the T240 alignment rod hole. It measures 0.315 [in] = 8.001 [mm]; consistent with what had been previously measured using flat-edged calipers; see pg 4-5 for pictures.)

Quantitatively confirming that the instruments are co-aligned with each other, and aligned well with the global IFO coordinates is difficult, at best, since there's no good alignment reference in this area. In attempts to quantify it, I've attached the coherence between each of the ground instruments and the T240s on the ISI in chamber. At the time, the platform had ST1 isolated and ST2 watchdog tripped (and I didn't check the status of HPI, but presumably if ST1 was isolated, HPI was robust isolated). That the platform was isolated sort of ruins the analysis, but it's something. Will ask the seismic team for advice.

Centering:
After moving/rotating the T240, the output signals remained saturated for ~5-10 minutes; not un-expected -- I've had the same experience with STS2s I've commissioned. Anxious to see if the instrument was saturated or rail/broken because of the move, I centered the instrument using the "Auto Z" button on the 4th chassis down (U18 of SEI-C1 rack -- see pg 9-11 of pictures), and the instrument went to zero within a second of the button push, but then veered off into lala land again shortly after. Waiting a few more minutes, and the signals came back into the ADC range. It still did not settle to zero mean within another 5 minutes, so I zeroed the instrument once more. Time series behavior was the same, so it just takes many many minutes to really settle. Again, no surprises here.

Calibration:
Sensor              Calibration
ISI T240s     1e-9      [(m/s) / (nm/s)]
GND T240s     1e-9      [(m/s) / (nm/s)]
PEM Guralp    7.6e-8    [(m/s) / ct]
pem.ligo.org suggest the calibration is "0.0076 [(um/s) / ct]," or 7.6e-9 [(m/s) / ct]. However, plotting this against the well-known (by my at least) calibrations of the T240s, the quoted PEM calibration appears low by a factor of 10. Hence, my calibration above.