J. Kissel, A. Neunzert, E. Goetz, V. Bossilkov

As we continue the investigation in understanding why the noise the region around 102.13 Hz gets SUPER loud at the beginning of nominal low noise segments, and the calibration line seems to be reporting a huge amount of systematic error (see investigations in LHO:72064), Ansel has found that some new electronics noise has appeared in the end station as of Saturday Aug 5 2023 around 05:30a PT at frequency extremely, and unluckily close to the 102.13000 Hz calibration line -- something at 102.12833 Hz; see LHO:72105.

While we haven't yet ID'd the cause, and thus no have a solution -- we can still change the calibration frequency to move it away from this feature in hopes that there're not beating together terribly like that are now.

I've changed the calibration frequency line frequency to 104.23 Hz as of 21:13 UTC on Aug 09 2023.

This avoids 
    (a) LLO's similar frequency at 101.63 Hz, and 
    (b) because the former frequency, 102.13 Hz was near the upper edge of the 9.33 Hz wide [92.88, 102.21) Hz pulsar spin down, "non-vetoed" band, this new frequency 104.23 Hz skips up to the next 18.55 Hz wide "non-veto" band between [104.22, 122.77) Hz according to LHO:68139.

Stay tuned 
   - to see if this band-aid fix actually helps, or just spreads out the spacing between the comb, and
   - as we continue to investigate the issue of from where this thing came.

Other things of note: 

Since
   - this feature is *not* related to the calibration line itself, 
   - this calibration line is NOT used to generate any time-dependent correction factors and thus the calibration pipeline itself, nor the data it produces is affected
   - this calibration line is used only to *monitor* the calibration systematic error, 
   - this feature is clearly identified in an auxiliary PEM channel -- and that same channel *doesn't* see the calibration line
we conclude that there *isn't* some large systematic error that is occuring, it's just the calculation that's getting spoiled and misreporting large systematic error.
Thus, we make NO plan to do anything on further with the calibration or systematic error estimate side of things from this.

We anticipate that this now falls squarely into the noise subtraction pipeline's shoulders. Given that this 102.12833 Hz noise has a clear witness channel, and the noise creates non-linear nastiness, I expect this will be an excellent candidate for offline non-linear / NONSENS cleaning.


Here's the latest list of calibration lines:
Freq (Hz)   Actuator                   Purpose                      Channel that defines Freq             Changes Since Last Update (LHO:69736)     
15.6        ETMX UIM (L1) SUS          \kappa_UIM excitation        H1:SUS-ETMY_L1_CAL_LINE_FREQ          No change
16.4        ETMX PUM (L2) SUS          \kappa_PUM excitation        H1:SUS-ETMY_L2_CAL_LINE_FREQ          No change
17.1        PCALY                      actuator kappa reference     H1:CAL-PCALY_PCALOSC1_OSC_FREQ        No change
17.6        ETMX TST (L3) SUS          \kappa_TST excitation        H1:SUS-ETMY_L3_CAL_LINE_FREQ          No change
33.43       PCALX                      Systematic error lines       H1:CAL-PCALX_PCALOSC4_OSC_FREQ        No change
53.67         |                            |                        H1:CAL-PCALX_PCALOSC5_OSC_FREQ        No change
77.73         |                            |                        H1:CAL-PCALX_PCALOSC6_OSC_FREQ        No change
104.23        |                            |                        H1:CAL-PCALX_PCALOSC7_OSC_FREQ        FREQUENCY CHANGE; THIS ALOG
283.91        V                            V                        H1:CAL-PCALX_PCALOSC8_OSC_FREQ        No change
284.01      PCALY                      PCALXY comparison            H1:CAL-PCALY_PCALOSC4_OSC_FREQ        No change
410.3       PCALY                      f_cc and kappa_C             H1:CAL-PCALY_PCALOSC2_OSC_FREQ        No change
1083.7      PCALY                      f_cc and kappa_C monitor     H1:CAL-PCALY_PCALOSC3_OSC_FREQ        No change
n*500+1.3   PCALX                      Systematic error lines       H1:CAL-PCALX_PCALOSC1_OSC_FREQ        No change (n=[2,3,4,5,6,7,8])