joseph.betzwieser@LIGO.ORG - posted 18:33, Tuesday 29 April 2025 - last comment - 15:45, Wednesday 28 May 2025(84181)
O4b uncertainty budget correction TF
Calibration is currently regenerating the O4b uncertainty budgets. Due to a missed change to the ETMX UIM suspension filters, which was found in LHO alog 82804, and then fixed only on Feb 27, 2025 (see LHO alog 83088), we need to add a correction TF to be included in the uncertainty budgets. I attach a graph of that correction TF (corrected model / original model) and the text file needed for that correction. We will be using correction TF in all our uncertainty budgets for O4b, and up to Feb 27, 2025 around 20:00 UTC, or GPS 1424721618 for O4c.
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Since after the July-Aug break, the low frequency response got closer to unity due to other mixed effects, we only apply the TF correction in uncertainty calculation before the break:
From 1396796418 = Wed Apr 10 15:00:00 UTC 2024 to 1404864018 = Sat Jul 13 00:00:00 UTC 2024
After the break, we leave it to GPflow to take care of the unmodeled residual using monitoring data.
Although the low-frequency response got closer to unity at later times, we found that GPflow still could not sufficiently capture the unmodeled residual.
We now determine that the above TF correction should be applied thoughout O4b at LHO.