Sad thing though, I should have realized, the decline of the driftmon now puts the camera image in jeopardy of being too close to the edge.  I had the enclosure open for a time and the cool down has pulled the drift signal down to -15660.  It could be 24 hours before things warm up enough to bring it back to before incursion level of -14000.

Ed has the BRSY engaged to nominal now but we are watching to make sure it is doing some good for the IFO.

We'll need to make another centering effort within a couple weeks.

BTW: prior to the DAQ restart it had been running for 28 days 0 hours and 38 minutes.

I ran coherence tool on these lines. I first tried to find a comb over there but failed. Then I tried to find them as single lines. I looked for 6 single lines: 12.125Hz, 48.5Hz, 60.625Hz, 72.75Hz, 84.875Hz, 97Hz. Two of them are not found in the coherence tool. Here are the results:

12.5Hz: https://ldas-jobs.ligo-wa.caltech.edu/~duo.tao/O2_line_12.125/index.html (Weak results and the structure does not look like a single line)

48.5Hz: https://ldas-jobs.ligo-wa.caltech.edu/~duo.tao/O2_line_48.5/index.html (Found in four of the weeks, in some EX and EY magnetometers. There are some channels that do not look like a single line. But there seems to be something going on so I showed them.)

60.625Hz: https://ldas-jobs.ligo-wa.caltech.edu/~duo.tao/O2_line_60.625/index.html (Not found)

72.75Hz: https://ldas-jobs.ligo-wa.caltech.edu/~duo.tao/O2_line_72.75/index.html (Not found)

84.875Hz: https://ldas-jobs.ligo-wa.caltech.edu/~duo.tao/O2_line_84.875/index.html (Weak. Only found in one channel and the structure does not look a single line)

97Hz: https://ldas-jobs.ligo-wa.caltech.edu/~duo.tao/O2_line_97/index.html (Found in many EX and EY magnetometers)

Robert's measurements seem to suggest that this is the resonance of one of the baffles.

https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=35166

That's 15:15UTC

15:20 UTC I also moved SUS ITMY to "SAFE" and took ITMY ISI to "OFFLINE" for CPS Noise investigations.

15:30UTC Due to impending PCAL work. BRSX is also off. Current state: "VERY_WINDY_NOBRSXY"

18:24 Hugh is finished his work and ITMY has been returned to it's nominal state(s)

Only the loudest of these saturated the noisemons, and it did so by hitting an analog limit at plus/minus 22000 counts.

I projected the drive signal into noisemon counts and looked at the last three injections on the list. In the first two, the noisemon signal tracks the drive, and the subtraction of the two is just noise. In the last (loudest) injection, the noisemon hits an analog saturation at both plus and minus 22,000 counts leaving a huge glitch in the subtracted data.

This is good because it suggests that the only important analog limit in the noisemon is this threshold. I don't have time to document it now, but I've tried the same with a set of loud detchar injections, which go up to hundreds of Hz, and I get the same behavior. So when the drive signal does not push the noisemon beyond 22,000 counts, we can trust the subtraction, and anything we see has entered the signal between the DAC and noisemon; it's a glitch in the electronics and not a result of the DARM loop.

Attached are the three subtractions, noisemon minus projected drive signal.

J. Kissel

Because the calibration suite requires one to turn OFF all calibration lines before the measurements then back ON after, the time-dependent correction factor computation is spoiled temporarily. In the GDS pipeline, which uses FIR filters, it takes about 2 minutes for the calculation to return to normal functionality and produce sensible results (Good! this is what's used to correct h(t)). However, because the front-end's version of this calculation (NOT used in any corrections of any astrophysical or control room product) uses IIR filters, it remains polluted until one manually clears the history on all filter banks involved in the process. 

Normally, as the ISC_LOCK guardian runs through the lock acquisition sequence, it clears these filter banks history appropriately. However, the calibration suite configuration is still a manual action.

Moral of the story -- I'd forgotten to do this history clearing until about 1 hr into the current observation stretch. The history was cleared at approximately  2017-03-22 00:10 UTC.

Why am I aLOGging it? Because clearing this history does NOT take us out of observation mode. Rightfully so in the case, because again the front-end calculation is not yet used in any control system, or to correct any data stream, it is merely a monitor. I just aLOG it so that the oddball behavior shown at the tail end of today's UTC summary page has an explanation (both 20170321 and 20170322 show the effect).

To solve this problem in the future, I'm going to create a new state in the ISC_LOCK guardian that does the simple configuration switches necessary so no one forgets in the future.

J. Kissel

On the discussion of "Why Can't LLO the same SNR / Coherence / Uncertainty below 10 Hz for These Sensing Function Measurements?"

It was re-affirmed by Joe on Monday's CAL check-in call that LLO cannot get SNR on 5- 10 Hz data points. There are two things that have been investigated that could be the reason for this:
   (1) The L1 DARM Loop Gain is too large ("much" larger than H1) at these frequencies, which suppresses the PCAL and SUS actuator drive signals.
   (2) Because of L1's choice in location of applying the optical plant's DC readout DARM offset and avoiding-DAC-zero-crossing-glitching SUS offset means there are single vs. double precision problems in using a very traditional DARM_IN1/DARM_IN2 location of the open loop gain transfer function.
both investigations are described in LHO aLOG 32061.

They've convinced me that (2) is a small effect, and the major reason for the loss in SNR is the loop gain. However, Evan G. has put together a critique of the DARM loop (see G1700316), which shows that the difference in suppression between 5-10 Hz is only about a factor of 4. I put a screen cap of page 4 which shows the suppression.

I attach a whole bunch of supporting material that shows relevant ASDs for both during the lowest frequency points of the DARM OLG TF and the PCAL 2 DARM TF:
     - DACRequest -- shows that a factor of 4 increase in drive strength would not saturate any stage of the ETMY suspension actuators
     - SNR_in_DARM_ERR -- shows the loop suppressed SNR of the excitation
     - SNR_in_DELTAL_EXT -- shows the calibrated displacement driven
     - SNR_in_OMC_DCPDs -- shows that a factor of 4 increase in drive strength would not saturate the OMC DCPDs 

 So ... is there something I'm missing?

Here with attached a plot showing comparison of PCal, CAL-DELTAL_EXTERNAL and GDS for the broad band injection. As expected, GDS agrees better with PCal injection signal. The code used to make the plot is added to svn,

/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/O2/H1/Scripts/PCAL/PcalBroadbandComparison20170321.m

Just to close out the question in Comment #2 above, LLO was indeed able to use LHO-like templates and drastically improve their SNR at low-frequency; check out LLO aLOG 32495. 

Hazaah!

J. Kissel, E. Goetz

The processed results for this data set are attached.

For context of how this measurement fits in with the rest of measurements taken during ER10 / O2, check out LHO aLOG 35163.