After finding this nice table describing the changes to the OM2 heater, I started growing suspicious of these changes because while also trying to chase down the 1.6611 Hz comb seen in h(t) (see LHO aLOG 71108), the dates seemed to align with each other that was too close to be coincidental.

Not knowing yet what channels I should look at for these changes, I just took a guess that H1:AWC-OM2_TSAMS_THERMISTOR_1_TEMPERATURE and H1:AWC-OM2_TSAMS_THERMISTOR_2_TEMPERATURE, would be a good enough proxy for seeing what changes might correlate with the comb changes. I took a trend of these channels since May 15 to July 27 to see those changes and then plot on top of them the changes I have seen in Fscan spectra over that time. The curves are the two channels and the vertical lines mark *approximate* times when a comb appears (red), changes to a lower level (yellow), or mostly vanishes (green). The vertical lines are pretty close to significant changes in the OM2 heater settings, at least according to what I can see with Fscan.

I suggest further investigation is needed here to understand what the heater is doing that could be adding line artifacts to the DARM loop and degrading the data quality in h(t).