[Louis, Elenna, with input from Sheila, Daniel, others] 

Elenna and I measured the PRC Gouy phase using the inertial kick technique used by Stefan et al in the past. Some relevant links to past PRC inertial kick measurements are 52504, 66215. Elenna's alog from a few days ago describing the SRC gouy results is also very relevant: 92136. 

We measure the single pass Gouy phase in the PRC to be 17.78° +/- 0.02°.

This differs from the most recent measurements in 2022 (66215, 20.66° +/- 0.17°) by about 2.88° and from the 2019 measurements (52504, 23.23° +/- 0.17°) by about 4.45°. 

Ring heaters were set to 0W during this test (92075).

Procedure

We followed the 'Measurement2' procedure from 52504. It took a few tries to get it right. We used H1:LSC-PRCL2_OUT as a trigger channel. We used an offset of -1e6 and used the engagement of said offset as the data start time. We got 5 kick measurements, ranging from 5 - 13 FSRs (page 1 of prc_gouy_sept_2026.pdf). 

The diaggui templates we used live as ~elenna.capote/inertial_gouy/PRC_gouy_kick<1-5>.xml. Those templates have a lot of channels. The primary channel used in my analysis is H1:LSC-POPAIR_B_LF_OUT. Unfortunately I did not get the corresponding IOP fast channel for that channel. It's not necessary but would have been nice to have to get more samples across each of the resonances. I did record the fast channel POPX segment data for future followup. 

I have a few thoughts on how we can get a better measurement next time there's an opportunity to repeat this. I'll state some brief comments here to remind future me to expand on this more clearly: 1.) it would be great to *not* feed REFL to PRCL during the measurement, 2.) we should revisit trying to hold MICH on a dark fringe instead of continuing to let it actuate during the swing, 3.) we should use the trigger method we used for SRC to get a more deterministic measurement, 4.) do we really need full PRMI to get this measurement?

Data Extraction 

I exported the trigger (LSC-PRCL2_OUT) and readback (LSC-POPAIR_B_LF_OUT) channel data to txt files stored at ~elenna.capote/inertial_gouy/prc_data/. There is a short description of what each txt file is in notes.txt. The processing script is at analyze.py in the same directory. It is also on gitlab.

Comments on Results

Before I started writing alog entry, I was quite concerned with the result of ~18° mostly because it seems like such a large deviation from the ~23° measurement from 2019. I didn't appreciate that the more recent 2022 measurement is much closer at 20.66°. As a sanity check for myself, I used my analysis script to process a subset of one of the preceding gouy measurements to make sure that I get a similar answer. I processed one of the 2019 measurements from 52504 and uploaded the resultant plot to prc_gouy_52504_sanity_check.pdf. My result is within 0.1° of what's reported in that entry. 

I don't yet have a good explanation for why the gouy phase has changed this much. The most 'obvious' thing to point at is the new bigger beam splitter. Sophie and I are planning to run some tests with Finesse this week to figure out what amount of lensing (presumably at the BBS) would account for the delta in gouy phase we're seeing in the PRC and SRC. 

In the attached prc_gouy_sept_2026.pdf I have several diagnostic plots: 

- Page 1: time series of each of the 5 measurements. vertical counts is from POPAIR_B_LF_OUT.
- Pages 2-6: overlays in time and fractional FSR spacing for each measurement set. both subplots are aligned so the 00 peaks lay at the horizontal origin. The temporal overlays indicate that the PRM was accelerating throughout the measurement. The changing velocity had to be accounted for. The FSR overlay shows the 01+10, 02+20 modes line up pretty well after using a cubic spline on the velocity. I believe the bump at 0.5 FSR could be the sidebands. 
- Page 7: the speed of the PRM through each measurement set (kick). The speed is evaluated at the mid point between each set of successive 00 peaks. 
- Page 8: displacement of the PRM across each measurement set (kick) as a function of time elapsed since the first 00 peak.
- Page 9: measured single pass gouy phases for each measurement set. The black horizontal line is the mean of the means and the gray shaded region spans mean +/- std mean error. The kick2 and kick3 measurements both contain outliers that deviate from the rest by more than their errorbars. This kind of thing can likely be tightened up by 1.) carefully retaking the measurement in a more deterministic configuration and/or 2.) being more careful of how I'm handing the changing velocity & identifying the peak centers through each swing. The contributed biases due to these outliers is nowhere near large enough to account for the change in phase being measured (~3-5°).

Some relevant links: 

- Stefan's 2019 measurement (52504) 
- Stefan's 2022 measurement (66215) 
- Our SRC gouy measurement from last week (92136) .

TITLE: 10/06 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Corrective Maintenance
INCOMING OPERATOR: None
SHIFT SUMMARY:

Comissioning team ran ISC_Lock up to Start_TR_CARM a few times which ended in locklosses and left it in Down for the night.
They put together an informative alog about their work that says that Initial Alignment WFS should hopfully work for input align and PRC, SRC!  

Camilla is planning to make a TCS ring heater change tonight around 8. I have put her on the Reservation system for that time as well.

LOG:                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      

Sheila, Elenna, Louis, Ryan Short, Jenne, Camilla,

Summary: We are still struggling with DRMI mode hopping, when we get past that we are struggling with the first steps of the CARM offset reduction.  We do have some initial alignment ASC working. 

• Ryan ran initial alignment and DRMI locked right away, with POP18 lower than on Friday (max 140 counts on I ERR DQ)
• lost lock once when the mode hoping offset came on, the next time while I was trying to measure TR_CARM
• We moved SR3 pitch so that the oplev agreed with what it was before turning the heater on (-1 in pitch), which is also closer to where it was inO4 according to the optical lever (0), reran SRY alignment manually.  In SRY, AS AIR sum was at 4920 counts, improved compared to 91957, both before and after the SR3 move. 
• We commented out the line that turns off the mode hoping offset in ISC_DRMI zero 3f offsets. 
• Measured MC2 crossover in START_TR_CARM, first attachment. It seems like we need to reduce the MCL gain by a factor of 2. We were able to reduce the TR_CARM Offset from -0.5 to -0.8, which is slightly better than other attempts where we couldn’t go higher than -0.7.  After we lost lock Elenna measured IMC MCL gain, it matched the reference. 
• Elenna edited ISC_DRMI guardian to have the BS oplev damping (which is running on the wit sensor) to only disengage if MICH ASC is on, so making use of the use_[PRMI/DRMI]_ASC flag in lscparams
• Louis moved PR3 according to M3 osems (pr3.png)
  • On Friday, PR3 suspensions jumped for some reason at 1475005715. There was a jump that was seen directly in PR3 at all stages (P, Y, and L). After the jump, all three stages of the PR3 suspension were sitting at different positions, according to the osems. About 18 minutes after the glitch, Corey moved PR3 back to the pre-jump positions according to the top mass osems. 
  • Today it was recognized by Sheila that the POPAIR_B buildups were lower than what was seen on Friday (before the suspension jump on PR3).
  • I (Louis) noticed that the position reported by the top mass didn’t agree with that of the bottom mass (or M2). Louis suggested that we rely more on the bottom stage osems and move PR3 back according to M3 osems instead.
  • Moving PR3 back to the M3 osem positions made the ALS Comm beatnote worse compared to when PR3 was aligned to the top mass osems. On the other hand, at the current position the beatnote power level matches what we had before the suspension glitch on Friday. So even though the comm beatnote is lower at the current alignment, we are leaving it as-is because it seems to better resemble the alignment we had on Friday before the suspension glitch.
  • ndscope template with markers set at the glitch and when Louis moved PR3 back today at ~louis.dartez/scopes/pr3_osems.yaml
• After moving PR3, we did initial alignment.  We paused at input align, Elenna phased refl wfs using a excitation in LSC XARM (6 screenshots attached of the phasing, sdf).  While she did that Sheila closed the Input align loops, with negative signs in INP1 P +Y, which is AS B 45.  We subtracted 180 degrees from all quadrants of AS B 45MHz (SDF).  
•   OPSINFO: We believe that next time someone does initial alignment, we should be able to run WFS for input align and PRC, SRC align, which we did run today. 
  • Must still do MICH dark by hand
• The strt_TR_CARM state failed, which you can see from the arm power fluctuating wildly.  To recover from this, 
  • zero the REFLBIAS gain, 
  • open the ALS COMM VCO screen (ALSO overview, VCO next to COMM PD), turn the servo to int and on (H1:ALS-C_COMM_VCO_CONTROLS_ENABLE), and set the H1:ALS-C_COMM_VCO_CONTROLS_SETFREQUENCYOFFSET to something like -2000, wait for the arm flashes to go away. 
  • Then you can manual to PREP_TR_CARM, try start_TR_CARM again
• We’ve tried setting the MCL gain to 150 (rather than the usual 300).  We tried skipping the step where we turn off FM4 in REFLBIAS and reducing the gain in the REFL servo in2.  We also tried a few more iterations of upping the gain by a factor of three, then stepping offsets.  It seems like there are some glitches that always get worse when we ramp down the ALS gain, and sometimes also when we reduce the CARM offset. 
• We are sort of centered on TMS QPD B for both arms. 
• Buildups today:
  • PRMI POP18 is 113
  • DRMI POP18 is 134, POP90 is 22
  • These buildups are lower than Friday but were not improved during our PR3 moves

WP13680. TJ, Camilla

When we started, the ALS beam hit the bottom periscope mirror high.

There is circles on the CCD camera indicating dust on some optics. We inspected and found a piece of dust on the bottom periscope mirror we could n to remove. We found a spare of this mirror but have not made the decision to swap or not yet.

Moved Pico 8 which is HWS X M1. We found the edge of the beam (crooked clipped) at +500 X and +1000 Y., then fell off around -2000. Leaving at X -100, Y -1017. With just this mirror we still had a lot of baffle in the camera view. 

TJ then moved the lower periscope mirror pico and could make the baffle take up less of the CCD with the beam staying well centered. Photo attached. 

[Rachel Langgin and Caroline Capuano]

Rachel and I volunteered to check if the alignment flucations were any worse than before IR1 upgrades (see commissoning meeting notes). To compare this, we check during O4c (gps 1444003218, October 9th, 2025) as our reference time and compared this spectrum with our most recent data from Tuesday (gps 1474675218, September 29, 2026) when everything was quiet. The script we used to make these plots can be found here.

Please keep in mind that this is comparing the old beam splitter to the new beam splitter so the change you see here could be related to that. This comparison can be re-run once we are locked for a more accurate comparison.

Optics_ASD_1444003218_vs_1474675218.pdf shows the ReferenceTime and CheckTime on the same figure for each optic, and Optics_ASD_1444003218vs1474675218-2.pdf shows the ratio between the two spectrums; both of these have a 60 second time span. Most of the optics do agree at higher frequencies, but a lot of them show differences in optics motion at low frequencies. Some optics shows some major motion differents below 10 Hz, like PRM, RM1, RM2, OM1 pitch and yaw, OM3, OMC.

Update:

Below are plots with a longer time span (10 minutes) and fft length of 64, and a different check time as well:

• Comparison: Optics_ASD_1444003218_vs_1471046418.pdf, Ratio: Optics_ASD_1444003218vs1471046418.pdf Check time: August 18th, 2026
• Comparison: Optics_ASD_1444003218_vs_1474070418.pdf, Ratio: Optics_ASD_1444003218vs1474070418.pdf

TITLE: 10/05 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Corrective Maintenance
INCOMING OPERATOR: Tony
SHIFT SUMMARY: Majority of the day was spent commissioning the mode hopping problem in DRMI and some work towards moving past TR_CARM (commissioners will post their own alog with the details). The LVEA is also Laser HAZARD for HWS table work.
LOG:

J. Kissel

As we explore the relationship between HAM3 - HAM2 differential motion with the SPI, it's forcing us to re-understand some ISI fundamentals. Brian made claims that we *shouldn't* use the ISI super sensors as metrics for the real displacement of the platform in LHO:92129, and points us to some math in T2500279. I wanted to back up the math with some plots of platform motion to help better visualize the math.

You can find plots of the current blend filters in use, in their dimensionless comparable form, from LHO:70527.
- the X/Y blend frequency is 0.18 [Hz] with broad gain peaking of around 1.5x to 2x from 0.03 - 0.6 [Hz].
- the RX/RY blend frequency is 0.375 [Hz] with more focused gain peaking of 4x from 0.1 to 1 [Hz].

Let's start with RX, since that's a relatively simple feedback loop, with no sensor correction complicating the math.
(RX-1) RX ASD (Blend Inputs vs. Blend Outputs vs. Super Sensor)
    - The input to the blend filters are shown in SOLID light blue (CPS) and green (GS13), compared with their sensor noise scaled to the RX degree of freedom (same color, just in dot-dot line style). Above ~1 Hz, the CPS is limited by its sensor noise, but also arguably below 0.1 Hz. Below 0.15 Hz, the GS13 is limited by its sensor noise. This implies that 
    - As we apply the blend filters to those input signals, we see what Brian describes in Section 2 of his document:
        . There's a hefty amount of gain peaking between 0.1 and 1 Hz [Hz] from the complementary blends, reporting a factor of ~4x more motion than at the input.
        . The CPS output is virtually identical in amplitude to the GS13 output up to 10 Hz.
        . The sum of the two blended outputs is "essentially zero" -- this is what we strive to understand.
    - There two channels, H1:ISI-HAM2_BLND_RX_FADE_OUT and then H1:ISI-HAM2_BLND_SUPS_RX -- test points in series just after the sum -- and just downstream's H1:ISI-HAM2_ISO_RX_IN1 that are equivalent and identical. 
    These two test points being identical to the ISO input is only true for DOFs where there's no input from the SUSINF external "sensor correction," either SUS offloading or CPS DIFF or SPI, as is true for the RX DOF -- knowing this will become important for DOFs that employ, e.g. CPS DIFF like the X DOF. I show the SUPS_RX and ISO_RX_IN1 channels here just confirm that there's nothing wild or crazy going on like "the signal changes as you exit up and out of a level in the simulink model," and to show that there's no external input from SUSINF. 

(RX-2) RX TF COH (Blend Outputs vs. Super Sensor)
    - This shows the linear coherence between each output to the blends and the super sensor.
    - assertion The CPS output's coherence is only non-zero where the CPS are actually measuring real platform motion where that signal appears above the sensor noise, between 0.1 and ~1 Hz.
    - The coherence of the GS13 output matches the coherence of the CPS below 10 Hz. assertion That implies that the GS13s are measuring the exact same thing as the CPS in this frequency region, whether it be real platform motion, or CPS sensor noise * the blend CPS filter.
     
(RX-3) RX TF PHA(Blend Outputs vs. Super Sensor)
    - This shows the (unwrapped) phase of the TF between the CPS blended output and the GS13 blended output w.r.t. the super sensor.
    - At least below ~3 Hz [Hz] it's obvious that the blended output of the CPS is exactly 180 [deg] out of phase with the blended output of the GS13
        Spot check of RX TF Phase at 0.5 [Hz]
            DISP OUT / SS       = 529.8 [deg] 
            INERT OUT / SS      = 349.8 [deg] 
            Difference          = 180 [deg]
      One can only trust the spot check at most frequencies if the blend filters are truly complementary. If they're not, then you've gotta be conscious of the "deviation from complementary" in the comparison. This will become important for DOFs where we push hard on the performance, like the X DOF.
    - Thus, the two signals, measuring exactly the same thing with the same amplitude below ~10 Hz, and when added together, given their phase relationship, you get a super sensor signal that's "essentially zero."

(RX-4) RX TF MAG (Blend Outputs vs. Super Sensor)
    - This shows magnitude of the TF between the CPS blended output and the GS13 blended output w.r.t. the super sensor.
    - Again, below ~10 [Hz], the GS13 and CPS blended outputs has the same transfer function magntiude w.r.t. the super sensor.
    - This -- especially is essentially a measure of the loop suppression
    - assertion where the TF is incoherent, the TF magnitudes loop suppression is reporting that the platform motion is dominated by suppressing sensor noise. In the case of the GS13s, its an independent measure of this loop-suppressed CPS noise that's dominating the platform motion.

TITLE: 10/05 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Corrective Maintenance
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 4mph Gusts, 2mph 3min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.11 μm/s 
QUICK SUMMARY: H1 in IDLE over the weekend; I'll start running some alignment to prepare for the day of locking progress. Found OM3 saturating, so I'll look into backing that off a bit.

In loop from 10/03 05:00 UTC (but only analyze from 05:30 UTC) to evaluate stability and possible tilt improvement from lower noise floor.
Had to reduce damping gain from 1 to 0.01, it looks like it was otherwise fighting with the isi loop. 

I've been in and out of the PCAL lab trying to test this new laser from CrystaLaser this week.
Thankfully I was able to connect with Dr. Jin out there and they steered me in the right direction.

When I first tried to test it I had the wrong power supply that couldn't keep up with current demands. As noted by the faintly lit current limit LED. The laser needs around 1.3 to 1.5 Amps to start up.

I've been finding that I had a fairly consistant TEM01 mode coming out of the laser it's self. I'm certain that the laser's been jostled around during shipping. After a few emails with Dr. Jin about this, Jin was able to guide me towards easily tweaking the laser to get a much better beam out of this laser head.

I was able to set up a beam profiler to do some preliminary beam profile data from a scanning slit profiler that was getting 1% of the beam out of a 1% beam splitter. 
the other 99% was sent to a power meter. 

Subject laser:
Make: CrystaLaser. 
Model: CL1047-2W0-ULG
Serial number: SN 460308-9464 
Gov #: G33348
Max power: 1.92W (measured after a 1% beam spliter.)
More beam profiler info comming soon. 
  

TITLE: 10/03 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Corrective Maintenance
INCOMING OPERATOR: None
SHIFT SUMMARY: We're still having trouble at TR_CARM. There was some weirdness with PR2 then SRM, I'm leaving IFO in down for the weekend.
LOG:                                                                                                                                                                                                                                             

~23:30 UTC While I was locking DRMI to then touch up SRM, after doing the same for PRMI and PRM, all of M3 and M1 LF RT immediately saturated with a huge signal coming from ISC L. Looking at the LSC SRC1 filter bank, we could see that the error signal could not reach positive 800 due to the offset of -800. Keita then turned off FM4 and the saturations stopped, turning it back on brought them right back. We were able to turn that filter off and on while seemingly remaining locked (if it was a real lock, heres  a plot of the sidebands power during PRMI then the subsequent DRMI, the levels are about the same) on DRMI 1f despite having no length feedback. The SRM alignment was likely bad, it "held" until I manually brought us down with ISC_LOCK.

TITLE: 10/02 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC

STATE of H1: Corrective Maintenance
INCOMING OPERATOR: Ryan C
SHIFT SUMMARY:

Today there was continued work looking at the lead-up to the CARM TO TR step for ISC LOCK.  For the most part DRMI reacquisition was fairly easy (Sheila alog-ed about a random PR3 move which was odd.) 

Toward the end of the shift, OM3's heater was increased from 1.0 to 4.0W for over the weekend.
LOG:

• 1437-1536 Manual Initial Alignment
• 1700-1740 EQ Mode Activated (M5.8 Russia)
• 1715-1829 CHETA laser hazard work (sophie)
• 1723-1732:  PRMI taking a while to lock, so touched up PRM & BS via PRX + MICH DARK align ifo states. (PRM moved the most (in pit), not much though); then back to PRMI_LOCKED.
• 1850-1925 Working on CrystalLaser (tony)
• 1915-1933 IR cavity alignment for PRM, BS, SRM again.
• 1948 While waiting for DRMI to lock, flashes all of sudden stopped.  RyanC noticed it was due to 
• 2100-2205 OMC dcpd function generator set-up in lvea, WP13679 (keita,alex)
  • But mentioned going out later.
• 2122-2209 Recording change made with  PCal CrystalLaser (tony, ryanC)
• 2312 Sheila requested us to take SR3's heater to 4.0 W (from 1.0W) for over the weekend.

Daniel, Sheila, Corey, Keita

Here are some comparisons of power build ups on POPAIR B:

Tony and Ryan Crouch found time for PRMI + DRMI without the arms from before the BS swap using state counter, they are writting an alog about that. 

We seem to now get more of an increase in build ups that we would expect from locking the arms, and we have more light on the diode than in O4.  We do not know if we might have had clipping in this in air path during O4. 

Some changes:

• leaving SRCL offset on for TR_CARM transition seems to help.  I have commented out line 1163 in ISC_DRMI, so the SRCL offset will stay on until we manually turn it off.  It may be better to use a larger offset, like -1200 counts.  
• With DRMI locked, after Corey fine tuned the alignment, we moved the SRCL offset around.  POP90 changes with the SRCL offset as shown in the attached screenshot. It seems like we need to keep POP18 above 200 counts to have a smooth time with the TR_CARM transition. 
• Moving the ALS COMM VCO a bit closer before starting the TR_CARM transition seems to help (-100 Hz offset instead of -200 Hz).  (this change is in lscparams).  
• PR3 jumped, 92170.  After this Corey put it back according to the top mass osems and then realigned MICH and PRX.  After this the build ups in DRMI were lower, but they were also more stable and we didn't have as much mode hopping.  
• We were able to go to the start_TR_CARM state, and with the above changes the guardian was able to once do this without intervention.  This means we can servo the arm transmitted powers, but something seems not stable here.  
• I tried to measure the TR_CARM loop gain, but the coherence is too low with the settings in our usual template (userapps/lsc/CARM/TR_CARM has excitation amplitude of 1).  I increased the loop gain by putting a 3 in TR_CARM where there is normally a 1, and increased the amplitude to 10.  We lost lock for an unknown reason, not the measurement.
• locking PRMI and DRMI has been slow.  Here is an old alog about the trigger levels 44348  When we ahave DRMI locked the MICH TRIG MONITOR (POP 18 norm) is around 100, based on this old alog I manually changed the trigger threshold to 27 and this seemed to help PRMI lock.  I've only tried this once and didn't put it in the guardian.  
• We are able to to strat_TR_CARM, with the SRCL offset on, then add a factor of 3 gain (in the input matrix or TR_CARM) and then step the TR_CARM offset to -0.8 without looseing lock.  I was only able to get a poor coherence measurement but it seems like this may have a ugf close to 100 Hz.  I do not understand why this is not stable, and stepping down the ALS gain seems to cause locklosses or large glitches.  

If anyone is looking for times that the PRMI is locked and the ALS COMM was Down, then Ryan C. Went ahead and found all those times for ya.
please see the following attached text files.

PRMI35-Locked_NoALS100_preBS.txt is a list of GPS time when H1:GRD-ISC_DRMI_STATE_N= 35 (in a PRMI state) AND H1:GRD-ALS_COMM_STATE_N = 100 (the Down State)

This was created via a tool called statecounter found in /ligo/gitcommon/statecounter. 

To run this particular command we used the following:
python3 statecounter.py -chan "H1:GRD-ISC_DRMI_STATE_N H1:GRD-ALS_COMM_STATE_N " -operator "==" -value "35 100" -trend "m-trend" -gpsstart "1198828818" -gpsstop "1459036818" --host h1daqnds0 -port 8088 -output "/ligo/home/anthony.sanchez/Documents/TonysOps/StateCounterResearch/PRMI35-Locked-NoALS100preBS.txt"

I also did the same for a bunch of DRMI states too which are included below.

Thanks for your help dividing and conquering Ryan C!
Thanks for the challenging question Sheila!

The CHETA X arm table telescope was fully aligned as described in gitlab. The performance of the telescope was determined by profiling the beam after L2 and calculating the complex q factor. The profile was measured using the nanoscan beam profiler over a 55cm range between M4 and M5.

This unit was profiled twice the first with a slight angle on L1 to prevent back reflection and then with a reduced angle to determine if this was detrimentally effecting the beam propogation. A non-linear fit was used in both cases to find the q factor which was propogated to the ITM to determine ITM beamsize. Both results show the horizontal axis have a large deviation from the expected q factor and the beamsize at the ITM is reduced by ≈35% and reducing the angle had a minimal effect.

Unit 0922 is noticibly non gaussian, screenshot attached, which we believe is consistent with what was observed by thorlabs and is indicated in a paper datasheet shipped to us with the unit. We believe this may be contributing to the deviation from the model.

Ryan Crouch, Corey, Sheila, Keita

After Corey aliged PRMI, and was waiting for it to lock, we suddenly lost the flashes in PRMI.  Ryan Crouch noted that PR3 moved, indeed there is a jump in all 6 top mass osems at the time that we lost the flashes.  Perhaps we need to investigate these electronics.

J. Kissel

As I'm building up my understanding the ISI system -- in order to eventually understand how to compare it to the SPI signals -- I found one thing I didn't like. 
When looking at the ISI data offline, we're typically looking at DQ channels -- i.e. those versions of test points that are stored in the frames -- so that we don't have to wait so long to gather data down to 1 [mHz]. 

Fine.

The native rate of the ISI front-end models is 4096 [Hz], so storing every interesting channel at the full data rate would be too much. As such, we down-sample some channels before storage.
Fine.

Of course, down-sampling requires a digital anti-aliasing filter, often referred to as the "DAQ down-sampling filter."
These are defined in T1600059 and the front-end in terms of "factor-of-reduction from native sampling frequency," e.g. if the native rate of the model is 4096 [Hz] and you chose to store the channel at 2048 [Hz], then you apply the "2x" filter. 

We store the inertial sensors, input to the blends e.g. H1:ISI-HAM2_BLND_GS13X_IN1_DQ at 4096 [Hz] so there's no downsampling filter involved.
Long ago, we decided that down-sampling the CPS to 512 [Hz] is good.
4096 / 512 = 8x.

But there's something very wrong with the 8x down sampling filter in the ISI system.
    (a) The DC magnitude of the transfer function between raw and DQ channel is 0.9954; i.e. a 0.5% gain loss.
    (b) The filter's ripple peaks at ~70 Hz with a magnitude of 1.0386.
    (c) The phase loss at 10 Hz is -9.1 [deg].

It's difficult to tell from the plots in T1600059 what the magnitude is doing, but I thought that these filters were normalized such that *either* the DC magnitude was 1.0, or the peak of the ripple is 1.0. Neither is true.
But, far worse -- the 8x filter phase in the design doc says its only losing -0.5 [deg] of phase at 10 [Hz].

We should fix the issue with the filter, and/or use a higher down-sampling rate.

If there's confusing stuff like this happening at such a base level, it makes it that much harder to interpret / compare the already confusing sensor signals.

Travis, Gerardo, Jordan, Betsy, Tyler, Richard

This morning we proceeded with the manual opening of GV20. Tyler had made a nice support for the input shaft on the gearbox to stabilize it while rotating the handwheel. This worked great, no additional oil leaked out of the gearbox after installation.

We had left the valve soft closed overnight, so we started raising the valve at 10:41:59 Pacific by turning the handwheel counter clockwise, stopping every 50 turns to check the ballnut/shaft collar gap. No issues found.

At turn 370, we tested to see if the handwheel would be driven backwards by the weight of the gate. No backwheeling was present, so we continued raising the valve stopping every 50 turns to check ballnut/ball screw height. At turn 620 we decided to increase the interval between stoppages to 100 turns. After turn 1520, the top of the ball screw was about even with the top of the clutch body. At 1920, there was enough exposed ball screw to install the safety plate and the locking collars. Locking collars were torqued to 140 in-lbs. 

We then continued raising the valve 300 turns (2") at a time, adjusting the lock collars at each interval, until the medm screen showed green.

Final turn count: 7161

Final ball screw height, +37.75" from top of clutch body (open position/green on medm) Note: Height stamped on side actuator body read 37 7/8" for the open position.

The interlock pin was then set, and lock collars were moved to top of safety plate, and torqued to 140 in-lbs. The handwheel was left installed on the gearbox with a clamp on it to prevent rotation.

Full set of compiled notes/details will be posted to the DCC with noises/turn counts/timestamps/ball screw heights/etc.