I was adjusting the alignment of MC1 pitch earlier, when the suspension had a large alignment shift that wasn't caused by a change in the requested drive to the DACs. The attached screenshot shows my requested alignment shifts in opticalign, and the resulting change in the requested DAC counts on T2 + T3. There is a sudden 420 urad jump in the osem readbacks from pitch, and a 133 urad jump in roll at the first time cursor. The master outs only see a few cycles on oscillations, which probably is from the damping loops responding to the jump, but they settle to the same requested drive as before the jump. The jump seems to be real as the IMC flashes disappeared at this time.
I ran an undamped no alignment offsets suite of transfer functions for MC1, and MC3, the state of HAM2 at the time was HEPI locked, ISI isolated. MC1 Pitch was the worst looking TF with multiple extra peaks. Looking at the OSEM signals for MC1 T3 shows a questionable drop during the time Sheila was looking at.
MC1:
/ligo/svncommon/SusSVN/sus/trunk/HSTS/H1/MC1/SAGM1/Data/
2026-03-06_1930_H1SUSMC1_M1_WhiteNoise_P_0p02to50Hz.xml
2026-03-06_1930_H1SUSMC1_M1_WhiteNoise_R_0p02to50Hz.xml
2026-03-06_1930_H1SUSMC1_M1_WhiteNoise_V_0p02to50Hz.xml
2026-03-06_1930_H1SUSMC1_M1_WhiteNoise_Y_0p02to50Hz.xml
2026-03-06_1930_H1SUSMC1_M1_WhiteNoise_T_0p02to50Hz.xml
2026-03-06_1930_H1SUSMC1_M1_WhiteNoise_L_0p02to50Hz.xml
MC3:
2026-03-06_2130_H1SUSMC3_M1_WhiteNoise_L_0p02to50Hz.xml
2026-03-06_2130_H1SUSMC3_M1_WhiteNoise_P_0p02to50Hz.xml
2026-03-06_2130_H1SUSMC3_M1_WhiteNoise_R_0p02to50Hz.xml
2026-03-06_2130_H1SUSMC3_M1_WhiteNoise_T_0p02to50Hz.xml
2026-03-06_2130_H1SUSMC3_M1_WhiteNoise_V_0p02to50Hz.xml
2026-03-06_2130_H1SUSMC3_M1_WhiteNoise_Y_0p02to50Hz.xml
I ran the same set of transfer functions for MC2 while Ryan did the other MCs; nothing suspicious here.
Templates' location: /ligo/svncommon/SusSVN/sus/trunk/HSTS/H1/MC2/SAGM1/Data/2026-03-06_2145_H1SUSMC2_M1_WhiteNoise_{P,R,T,V,Y,L}_0p02to50Hz.xml
Remeasuring MC1_P after Marc swapped the coil driver reveals that the coil driver was not the issue.
