Sheila, Anamaria

I made spectrograms of the scan from the previous night, which ran for close to 10 hours. We notice similar lines appearing and disappearing with the VCO frequency, like we do at LLO. This is encouraging, in that our best guess is that it's some artifact of the VCO electronics.
On the other hand, unclear what it means for whistles in full lock. There seem to be larger swaths of VCO frequencies (than at LLO) where nothing happens, so that's one option for explaining why LLO DARM whistles and LHO DARM does not. (We hope these lines are a symptom of the same phenomenon as in full lock, when MCF moves by 10s of kHz and these lines would become whistles,but we don't know)
Figures for the full scan, in 100 sec increments, can be found at: https://llocds.ligo-la.caltech.edu/data/dtt/Anamaria/public/imcvco/LHOsweepJul23/

The plots show whitened spectrograms:
- IMC-F at the top with a green overlay of the IMC-F DC value which would have to be multiplied by 3 to be true Hz;
- ISS out of loop sensor, with a yellow overlay of the VCO frequency, in Hz, but with the starting frequency subtracted (the value at bottom left) and shifted by 3kHz to be in the approx middle of the graph;
- the OMC-DCPD_SUM spectrogram.

I attach four examples:
- lines only seen in OMC, first plot
-lines seen in both OMC and ISS, second plot
- two different "orders" in MCF only, third and fourth plots.