craig.cahillane@LIGO.ORG - posted 15:19, Thursday 30 June 2016 - last comment - 18:12, Thursday 30 June 2016(28096)
Actuation function measurements never had time-dependence removed
C. Cahillane After taking a close look at the Hanford actuation measurements, with the addition of the January 7th measurements, it became very obvious that the actuation measurements were never compensated for time dependence. I am not sure if the same is true at Livingston. I will be investigating shortly. If so, it could be a major reason why LLO actuation uncertainty is so large... Previously, I used only calibration-week actuation measurements for LHO, meaning the kappas could not have varied too crazily in that period. But LLO had measurements more spread throughout the run. This is obviously quite important for our uncertainty budget... The systematic errors will be affected on the order of the kappas that were never applied, so about 3% for TST and 2% for PUM and UIM. The uncertainties will be smaller since removing time-dependence will cluster our measurements better. I have posted a plot similar to the one from aLOG 27290 showing the actuation magnitude variances and covariances between each day's measurements. Blue is the measurements without the kappas applied. Red is with the kappas applied. Comparing to aLOG 27290, we see UIM and PUM variances stay about the same, which makes sense because kappa_pu is not that volatile. But TST variance goes from2.5%to2.0%! I have added the following scripts to the calibration repository:analyze_pcal_20150928_kappa_corr H1PCALparams_20150826_kappa_corr H1PCALparams_20150828_kappa_corr H1PCALparams_20150829_kappa_corr H1PCALparams_20160107_kappa_corrThese allow me to correct the LHO time dependence in our actuation functions.
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C. Cahillane I have propagated the new actuation systematic fits and uncertainties through to the final response function comparison R_C02/R_C03. The plot shows in dark red the old variance-only uncertainty and systematic error for R_C02/R_C03 reported to the PE group. The new covariance-included and correctly time-dependence compensated LHO actuation systematic error in light red. The results are dramatic. Without the DC positive biases in the actuation functions, the LHO sensing function systematic error takes over at low frequency. This pushes the LHO systematic error at 11 Hz from +5% to +9% This means the overall "deviation" at LHO is above 10% in magnitude at 15 Hz for C02 at GPSTime = 1135136350, the time of the Boxing Day event I have looked through the Livingston actuation measurements and convinced myself than a similar mistake does not exist there. As far as what I reported to the PE group for "C03", it is significantly off in both magnitude and phase due to this bug and the addition of covariance. I will update all of the O1 uncertainty results based on this information.
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