J. Kissel, L. Dartez

On Friday we generated a new calibration report in anticipation of updating the LHO calibration, a process discussed in LHO:69563. The report can viewed at https://ldas-jobs.ligo-wa.caltech.edu/~cal/archive/H1/reports/20230510T062635Z/H1_calibration_report_20230510T062635Z.pdf. You can view all of the report's contents by removing the file stub at the end of path (or by clicking here). 

In short, we believe we're ready to update the calibration for LHO to reflect several changes to the sensing function that have been implemented over the past few weeks* (LHO:69402, 69359, 69358, 69487, 69478).



Before generating this report, we carried out various "checks" and preparation steps to improve our confidence in the estimated calibration parameters.


Process measurements taken with a fully thermalized IFO
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We pruned the sensing function measurements we had in the can** to ensure that only measurements taken with a thermalized IFO were processed. Measurements (especially those of the sensing function) taken while the IFO is still thermalizing, during which the sensing function is in a constant state of flux, will result in inconsistent GPR results and throw off our estimation of the optical gain, coupled cavity pole frequency, quality factor, and spring frequency. I moved the "unthermalized" measurements into a new directory titled "unthermalized" within the measurements directory. This is not an optimal part of the workflow we would like to support going into O4 so it'll need to be addressed down the road. The thermalization state was checked by inspecting H1:ASC-Y_PWR_CIRC_OUT16 and H1:ASC-X_PWR_CIRC_OUT16 in ndscope.

GPR frequency range
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We moved the lower limit of the GPR fit range down to 5Hz to include the low frequency content (<10Hz). Doing so resulted in much more sensible GPR output at low frequencies. We are using the same GPR kernel as in O3 (LHO 55012).


Confirm optical gain calculation
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We confirmed that the estimated optical gain almost exactly matches the old optical gain value * Kappa$$C. 


Coupled Cavity Pole Frequency Estimation
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We noticed that Fcc is off by ~4Hz. We're not sure why at this point but we're not too concerned; the Fcc Kappa TDCF will take care of this discrepancy for us in the front end.


Reports included in the current epoch.
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20230504T055052Z epoch epoch-sensing epoch-actuation
20230505T012609Z 
20230505T174611Z 
20230505T200419Z 
20230506T182203Z epoch-sensing
20230508T180014Z 
20230509T070754Z 
20230510T062635Z 


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* assuming that the ongoing attempts to suppress the ~4Hz bumps in DARM do not affect the sensing function

** All (LHO) calibration measurements made by pyDARM are stored in /ligo/groups/cal/H1/measurements/.