J. Kissel

Seeing the "first light," calibrated SPI Optical Lever amplitude spectral densities in  and , and thinking about ADC noise limitations and the calibration models assumption that the spots are centered on the QPDs drove me to re-check the spot positions on the QPDs. 

Timeline of centering:
    2026-07-17 17:00 UTC (LHO:91124) -- Jennie turned on the SPI laser for the first time since doors went on and the ISIs were isolated, and re-centered *only* QPDB with M_C1 (and thought she had adjusted QPDA centering with M_M1, thought she had mistakenly moved M_M2, but confirmed later she did not; LHO:91219).
    2026-07-23 14:00 UTC (LHO:91218) -- Jim unlocks and restores function of HAM2 HEPI, such that now both HAM2 and HAM3 are fully functional, and remain ISOLATED with corner station sensor correction ON as their nominal condition.
    2026-07-23 20:30 UTC (LHO:91221) -- Jennie re-centered (only) QPDB again using M_C1.
    2026-07-24 16:05 UTC (this aLOG) -- Not knowing that Jennie had yet recentered any QPDs, and finding QPDA PIT's normalized beam displacement at +0.23 [rad], I recentered *both* QPDA and QPDB.

I attach a similar trend of relevant channels including both Jennie's centering work from 2026-07-23 and mine this morning. Similar to Jennie's plots but with thick lines, light mode, and with the y-axes labeled.
I saved this template to 
    /opt/rtcds/userapps/release/spi/h1/ndscope/QPD_Centering.yaml  (rev 35598).


Here're the DC values of the QPDs after this morning's centering (done with the precision one can achieve with a picomotor STEP SIZE of 1 [ct]):
$ gpstime now;z avg -30 H1:SPI-H23_OL_QPD_A_PIT_OUT_DQ H1:SPI-H23_OL_QPD_A_YAW_OUT_DQ H1:SPI-H23_OL_QPD_B_PIT_OUT_DQ H1:SPI-H23_OL_QPD_B_YAW_OUT_DQ -s

t = 
PDT: 2026-07-24 09:27:44.113664 PDT
UTC: 2026-07-24 16:27:44.113664 UTC
GPS: 1468945682.113664

Channel                        t-30 sec average       t-30 standard deviation
H1:SPI-H23_OL_QPD_A_PIT_OUT_DQ -0.0024822048842906954 4.722167842008142e-06
H1:SPI-H23_OL_QPD_A_YAW_OUT_DQ  0.0030039884615689514 5.884913671432033e-06
H1:SPI-H23_OL_QPD_B_PIT_OUT_DQ -0.0022898733150213957 8.094109742945136e-05
H1:SPI-H23_OL_QPD_B_YAW_OUT_DQ  0.008859152471025783  4.6337990240392655e-05

$ gpstime now;z avg -30 -s H1:SPI-H23_OL_QPD_A_PIT_OUT_DQ H1:SPI-H23_OL_QPD_A_YAW_OUT_DQ H1:SPI-H23_OL_QPD_B_PIT_OUT_DQ H1:SPI-H23_OL_QPD_B_YAW_OUT_DQ H1:SPI-H23_OL_QPD_A_SUM_OUT16 H1:SPI-H23_OL_QPD_B_SUM_OUT16

t0 = 
PDT: 2026-07-24 09:54:54.983607 PDT
UTC: 2026-07-24 16:54:54.983607 UTC
GPS: 1468947312.983607

Channel                        (t0-30 sec) average       (t0-30 sec) standard deviation
H1:SPI-H23_OL_QPD_A_PIT_OUT_DQ  -0.002713  3.4e-05
H1:SPI-H23_OL_QPD_A_YAW_OUT_DQ   0.003265  4.2e-05
H1:SPI-H23_OL_QPD_B_PIT_OUT_DQ  -0.002033 10.0e-05
H1:SPI-H23_OL_QPD_B_YAW_OUT_DQ   0.009682 5.3e-05
H1:SPI-H23_OL_QPD_A_SUM_OUT16   25.846691 0.003820814636259141
H1:SPI-H23_OL_QPD_B_SUM_OUT16   29.265472 0.004081774857250754