As we are gearing up to regenerate our hourly uncertainty estimates spanning back to the start of O4, I needed to go back through the history of LHO calibration changes, the IFO changes they address, and the identification and placement of each new epoch for the sensing and actuation functions. The table below lists the calibration epochs since the start of O4. For each epoch, I include some relevant alogs that chronicle which IFO changes triggered each epoch. More in depth information on each change to the LHO calibration pipeline can be found in the living Record of Real-Time Calibration Pipeline Parameter Changes (DCC: T2300297).



  
Date
  
Epoch Type
  
Reason for new epoch


  
20230504T055052Z
  
Sensing, Actuation
  
new SRCL offset (LHO:69289), TCS changes (LHO:69032), and PCALX cal line change (LHO:69303). More in LHO:69332. This report was *not* exported to the front end.


  
20230506T182203Z
  
Sensing
  
Changed SRCL offset, DARM loop. More in LHO:69561. N.B. This report marks a new epoch for the sensing function but it did not get exported to the front end (i.e. the "calibration" was not updated using this report). Instead, the report that was used to update the calibration and includes the IFO changes listed in LHO:69561 is 20230510T062635Z.


  
20230621T191615Z
  
Sensing
  
Moved back to 60W input power(LHO:70693). 20230621T191615Z marks the start of the epoch but the report used to update the IFO calibration is 20230621T211522Z.


  
20230628T015112Z
  
Sensing
  
OM2 was heated (first time). See LHO:70849.


  
20230716T034950Z
  
Sensing
  
OM2 was unheated. See LHO:72524.


  
20230727T162112Z
  
Sensing
  
OM2 was reheated. See LHO:72523.


  
20230817T214248Z
  
Actuation
  
3.2kHz filter restored in L3 actuation path. See LHO:72043



Several of the calibration reports had not been properly tagged yet to reflect the epoch boundaries defined above. I manually went through each one and made sure to do so, but this necessitated the reprocessing/regeneration of several calibration reports to ensure that the GPR calculations for the sensing and actuation functions only included the relevant set of measurements. Here is a list of the reports that were reprocessed with the appropriate epoch boundaries. Before being overwritten each report was backed up to /ligo/groups/cal/H1/reports/archive/.

06/21  reason: 60W
06/27 14:53 : om2 hot
    20230628T015112Z [regenerated for epoch-sensing]
07/12 16:05 : om2 cold
    20230716T034950Z [regenerated for epoch-sensing]
07/19 08:15 : om2 hot
    20230727T162112Z [regenerated for epoch-sensing]
    20230802T000812Z [regenerated for new epoch-sensing]
    20230817T214248Z [regenerated for epoch-actuation]
    20230823T213958Z [regenerated for new epoch-sensing and new epoch-actuation]
actuation:
05/04: start of O4
08/08: 3.2kHz filter
    20230817T214248Z [regenerated for epoch-actuation]