I ran 3 BNC cables from the SP table to 1X7 rack so that we can have 16 bit channels for the Ontrak PD that will be used to test oplev lasers. The BNC cables are plugged to the Ch 29, 30 & 31 that were already created for this purpose (elog 10488)

[Koji, Jenne, Diego]

Summary:  We really don't have any MICH signal in REFL 165.  Why is still a mystery.

We made several transfer function measurements while PRMI was locked on REFL33 with the arms held off resonance, and compared those to the case where the ETMs are misaligned.  We fine-tuned the REFL165 demod phase looking at the transfer function between 10-300 Hz (using bandpassed white noise injected in the MICH FF filter bank and looking at REFL165Q), rather than just a single line.  We did that at CARM offset of 3 counts (ALS locked), and then saw that as we reduced the CARM offset, the coherence between MICH injection and REFL165Q just goes down.  Any signal that is there seems to be dominated by PRCL. 

So, we're not sure why having the arms eats the MICH 165 signal, but it does.  Everyone should dream tonight about how this could happen. 

Koji suggested that if the signal is just lost in the noise, perhaps we could increase our modulation depth for 55MHz (currently at 0.26, a pretty beefy number already).  Alternatively, if instead the problem is that the MICH signal has rotated to be in line with the PRCL signal, there may be no hope (also, why would this happen?).

Anyhow, we'd like to understand why we don't have any MICH signal in REFL165 when the arm cavities are involved, but until we come up with a solution we'll stick with REFL33 and see how far that gets us. 

The only really worthwhile plot that I've got saved is the difference in these transfer functions when PRMI-only locked and PRMI+arms locked.  Green is PRMI-only, with the demod phase optimized by actuating on PRM and minimizing the peak in the Q signal.  Blue is PRMI with the arms held off resonance using the ALS signals, with the demod phase set again, in the same way.  We were expecting (at least, hoping) that the blue transfer function would have the same shape as the green, but clearly it doesn't.  The dip that is around 45 Hz can be moved by rotating the demod phase, which changes how much PRCL couples into the Q phase.  Weird.  At ~3nm we had somewhat reasonable coherence to RELF165Q, and were able to pick -102deg as the demod phase where the dip just disappears.  However, as the CARM offset is reduced, we lost coherence in the transfer functions.

[Diego,Koji]

Today we took some measurements of transfer functions and power spectra of suspensions of the MC* mirrors (open loop), for all the DOFs (PIT, POS, SIDE, YAW); the purpose is to evaluate the Q factor of the resonances and then improve the local damping system.

[Diego, Jenne]

The script is moving forward and we feel we are close, however we still have a couple of issues, which are:

1) some python misbehaviour between the system environment and the anaconda one; currently we call bash commands within the python script in order to avoid using the ezca library, which is the one complaining;

2) the fine scan is somewhat not so robust yet, need to investigate more; the main suspects are the wavelet parameters given to the algorithm, and the Offset and Ramp parameters used to perform the scan.

Here is an example of a best case scenario, with 20s ramp and 500 points:

Earlier today, I did some simulations that suggested that PRC lengths on the order of a cm from our current estimated one could result in degenerate PRCL and MICH signals in REFL165 at 3nm CARM offset. I attempted more demod-angle derived cavity PRC length measurements with REFL11 and REFL55, but they weren't consistent with each other...

In any case, adding dual recycling, even with a SRC length off by 1cm in either direction, doesn't seem to exhibit the same possibility, so I spent some time tonight seeing if I could make any progress towards DRMI locking. 

I was able to lock SRY using AS55 in a very similar manner to PRY, after adjusting the AS55 demod angle to get the error signal entirely in I. I used this configuration to align the SRM to the previously aligned BS and ITMY. Oddly, I was not able to do anything with SRX as I had hoped; the error signal looks very strange, looking more like abs(error signal). 

I then was able to lock the SRMI on AS55 I & Q, the settings have been saved in the IFO configure screen.  I've used AS55Q for PRMI locking with a gain of -0.2, so I started with that; the final gain ended up being -0.6. PRMI/PRY gain for prcl is something like 0.01, so since I used a gain of 2 for locking SRX, I started the SRCL gain around 0.02, the final gain ended up being -0.03. I basically just guessed a sign for AS110 triggering. Once I lucked upon a rough lock, I excited the PRM to tune the AS55 angle a few degrees; it was luckily quite close already from the SRY adjustment. AS110 needed a bigger adjustment to get the power into I. (AS55: -40.25->-82.25, AS110: 145->58, but I put AS55 back for PRMI)

I briefly tried locking the DRMI, but I was really just shooting in the dark. I went back and measured various sensing amplitudes/angles in SRMI and PRMI configurations; I'm hoping that I may be able to simulate the right gains/angles for eventual DRMI locking.

The PSL HEPA stopped working while it was running at 80%. I have closed the PSL enclosure.

Steve is working to fix this.

 The Variac burned out and it was replaced. Each unit was checked out individually. HEPA -north is still noisy at full speed.

Preparations

- According to Diego's report, the MC WFS gains were too high. We'll fix this later by tweaking the servo shapes.
But for now, all of the WFS gains were reduced by 40%.
i.e. WFS(1|2)(PIT|YAW) gains from 5 to 3, MC2TRANS(PIT|YAW) gains from 50 to 30.

- Aligned IMC carefully and ran the offset nulling script. MC REFL became 0.435~0.445 and MC TRANS was ~16600.

- Locked the arms and ran ASS.

PRMI

- Started locking PRMI. I just used REFL33I&Q as suggested by the configure script. The PRMI locking was not so robust.
Particularly, the third violin mode of PRM and BS seemed to get excited and dominated the signals.
I modified Vio3 filter in the violin filter for BS and PRM to include zero at 1921Hz where the growing peak was seen.

- We probably want to start from the 1f signals for DRMI lock acquisition. So I wanted to check how REFL11s are.
Measured the demod phase and relative gain between 33I and 11I. (By the way, REFL11I whitening gain was lowered to 0dB).
REFL11I had about x10 gain and the same phase compared to REFL33I. The demod phase for REFL11 was +21deg.
Also checked REFL55 phase and gain. 55Q has almost the same gain as 33Q. And the adjusted phase was 25deg.
These were just rough adjustment of the demod phases.

- Then the servo configuration was transtioned to Configuration 1 (below), and then Configuration 2.

- This configuration was very stable and the PRMI stayed locked about ~1 hour. During this long lock, I could measure 
PSDs, sensing matrix, and etc. Also I could play with the PRM ASC. I wasn't sure if the POP is actually stabilized or not.
(I have no data)

- I noticed that something was ringinging up at 1883Hz. Another 3rd order viloin mode???

- The lock was lost due to too strong injection. But also it reacquired without touching.

- Precise demod phase adjustment has been done by elliminating PRCL from the Q signals.

REFL11 16.75
REFL33 133.0
REFL55 31.0
REFL165 -142 
AS55 -53

- Configiration1 (REFL11I&REFL55Q)

REFL11: WTN 0dB PHASE 21deg, REFL11I x0.1 -> PRCL
REFL33: WTN 30dB PHASE 145deg
REFL55: WTN 21dB PHASE 25deg, REFL55Q x1 -> MICH

PRCL: GAIN -0.04 FM4/5 ON, Triggered FM 2/3/6/9, Servo trigger: POP22I 50up 10down, No Normaization.
MICH: GAIN 10 FM4/5 ON, Triggered FM 2/3/6/9, Servo trigger: POP22I 50up 10down, No Normaization.

PRCL -> PRM +1
MICH -> PRM -0.2625, BS +0.50 BS

- Configuration 2 (REFL11I&Q)

Same as above except:
REFL11Q x-0.1 -> MICH

Calibration

Let's use these entries 

PRM: http://nodus.ligo.caltech.edu:8080/40m/8255
PRM:  (19.6 +/- 0.3) x 10^{-9} (Hz/f)^2 m/counts

BS/ITMs http://nodus.ligo.caltech.edu:8080/40m/8242
BS     = (20.7 +/- 0.1)    x 10 ^-9 / f²
ITMX = (4.70 +/- 0.02)  x 10 ^-9/ f²
ITMY = (4.66 +/- 0.02) x 10 ^-9/ f²

- PRCL Calibration

Lockin oscillator module 675.13Hz 100 -> +1 PRM

Measurement bandwidth 0.1Hz -> Signal power BW 0.471232 (FLATTOP window)

C1:SUS-PRM_LSC_IN1: 118.99 cnt/rtHz => 5.12pm/rtHz
REFL11I: 17.84  cnt/rtHz => 3.49e12 cnt/m
REFL33I:  2.28  cnt/rtHz => 4.46e11 cnt/m
REFL55I:  0.158 cnt/rtHz => 3.09e10 cnt/m
REFL165I: 1.63  cnt/rtHz => 3.19e11 cnt/m

- MICH Calibration

Lockin oscillator module 675.13Hz 100 -> -1 ITMX +1 ITMY

Measurement bandwidth 0.1Hz -> Signal power BW 0.471232 (FLATTOP window)

C1:SUS-ITMX_LSC_IN1: 121.79 cnt/rtHz => 1.26pm/rtHz
C1:SUS-ITMY_LSC_IN1: 121.79 cnt/rtHz => 1.25pm/rtHz
REFL11Q:  0.0329   cnt/rtHz => 1.32e10 cnt/m (PRCL/MICH ratio 265)
REFL33Q:  0.00773  cnt/rtHz => 3.09e9  cnt/m (144)
REFL55Q:  0.001645 cnt/rtHz => 6.58e8  cnt/m (47)
REFL165Q: 0.00374  cnt/rtHz => 1.50e9  cnt/m (213) !?
AS55Q:    0.0696   cnt/rtHz => 2.78e10 cnt/m

Openloop TF measurements
Servo filter TF measuremnts

The UGFs were ~250Hz for PRCL and ~120Hz for MICH, respectively.
The OLTF was modelled by the servo and violin filters TF from foton, estimated TF of the AA/AI filters, and the constant time delay.

Displacement spectra measurement

SELF NOTE: DON'T FORGET TO TURN ON the whitening of the unused signals! (USE MC DOF or manual switch)

- PRCL

The PRCL displacement was measured with REFL I signals. In the attachment 3, the in-loop and free-run equivalent displacements are shown (red and blue).
Other out-of-loop sensors (33/55/165) were also plotted together.

FIrst of all, the uncompensated displacement noise level of PRCL is around 1e-7 m/rtHz. This is a good indication that the calibration was not crazy.

The sensing noise of REFL11 seems to be 1e-15~1e-16 m/rtHz at high frequency which is enough for now.
As expected, REFL11I has the best noise level among the REFLs. At low frequency, it seemed that the noise level is limited by something at 1e-12 m/rtHz.
Of course, we can't say this is just the sensing noise of the other REFLs or the noise of the REFL11I. But this noise level is enough small for the locking of
the low finesse (F<100) PRCL cavity.

Remembering we had no trouble locking PRCL with REFL33/55/165, this plot indicates that the PRCL was suppressed too much below 2Hz.
And we want more supression between 5Hz to 30Hz. We have resonant gains in ther PRCL servo but not sure how effective they were.
If we consider the contamination of PRCL in MICH, we should try to optimize the PRCL servo.

- MICH

The MICH displacement was similary calibrated to PRCL. The signal sources were the REFL Qs and AS55Q.
In the attachment 4, the in-loop and free-run equivalent displacements are shown (red and blue).
Other out-of-loop sensors were also plotted together.

The problem here is that the out-of-loop levels (REFL33/55/165 and AS55) show almost the same levels
and thus it is likely that the actual (out-of-loop) stability of MICH is this kind of level. If we believe it, we only have
~1/100 supression between 1-10Hz and ~1/10Hz below 0.5Hz. The strong servo control does nothing to stablize
MICH. From the out-of-loop noise level of MICH, this comes for the contamination from leakage PRCL.
We really need to improve the signal quality of MICH.

The MICH servo filter has quite complicated shape, but is not necessary according to the estimated free-runing MICH.

The MICH free-running motion is quieter than the PRCL one between 1Hz to 30Hz. The reasonable explanation is
that it comes from poor vibration isolation of the tip-tilts. It means that SRCL also has the similar noise level to PRCL.

Something to note, as we have the IMC angular controls under consideration:

Jenne has the DRMI locked right now. I took a look at the coherence between the POP QPD and MC2 transmission QPDs. (Since she's using ASC, I also included those control signals. The coherences are about the same, unsurprisingly)

Based on the observed coherences, from about 1 to 6Hz, IMC motion is responsible for a fair amount of the DRMI angular motion. Also, PIT and YAW couple differently. 

I wonder if this is the coherence caused by the beam itself, or caused by the same ground motion.
Jenne should be able to tell us...

SRM Calibration

After the DRMI measurements on Friday, SRY cavity was locked in order to compare ITMY and SRM actuators.

SRY cavity was locked with AS55Q ->  SRM servo with gain of +10?
(My memory is fading. I tried +50 and noticed it was saturated at the limiter. So I thought it was 10)

Then the transfer functions between SRM->AS55Q TF and ITMY->AS55Q TF were measured.

The ratio between two transfer functions was obtained as seen in the second attachment.
The average at f<100Hz was 4.07 +/- 0.15. Therefore the calibration is ... as you can find below

SRM: http://nodus.ligo.caltech.edu:8080/40m/10664
SRM = (19.0 +/- 0.7) x 10 ^-9/ f²

PRM: http://nodus.ligo.caltech.edu:8080/40m/8255
PRM:  (19.6 +/- 0.3) x 10 ^-9 / f² m/counts

BS/ITMs http://nodus.ligo.caltech.edu:8080/40m/8242
BS     = (20.7 +/- 0.1)    x 10 ^-9 / f² m/counts
ITMX = (4.70 +/- 0.02)  x 10 ^-9/ f² m/counts
ITMY = (4.66 +/- 0.02) x 10 ^-9/ f² m/counts

Summary: Cannot find beatnotes between the arms and PSL.

I wanted to measure the ALS out of loop noise before putting stuff on the PSL table for frequency offset locking.

But I was not able to find the beat notes between the arms and PSL green. All I could find while scanning through the end laser temperatures is the beatnote between the X and Y green.

EricQ says that he spent some time yesterday and could not find the beatnotes as well.

Debugging and still could not find:

1. Checked the FSS slow actuator. This was close to zero ~0.003

2. Checked the green alignment on the PSL table. Everything seems fine.

3. Checked the actual PSL laser temperature. It was 31.28deg and not very far from when it was last set at 31.33deg elog.

4. Also checked the end laser temperatures. Both the lasers are ~40deg (where I could see the beatnote between the arms). Based on the plot here and  here , we are very much in the regime where there should be a beatnote between the PSL and the arms.

I've fallen down the rabbit hole of trying to reconcile our desire for newer versions of the Numpy and Scipy python packages with the use of our handy cdsutils tools. 

I've set up an installation of Anaconda python in /ligo/apps/anaconda. Installing pyepics, nds2, and cdsutils was straightforward, but there were a myriad of odd python packages that cdsutils depends on, that are typically installed at the OS level (python-gst, gobject, glib) which I just manually copied over to the anaconda directories. Also, the version of readline that anaconda ships with is somewhat borked (dark voodoo fix was found here: github link. The issue mentioned there wasn't why I needed the fix. Somehow libreadline was causing pyepics initialization to fail). 

I was initially hoping this kind of exercise would be useful, as having a separate python environment that we control buffers us from the system installation and allows us to use whatever version of packages we want, but the amount of hackery I did to get to get cdsutils to work probably didn't result in the most robust solution. (Maybe there was a better way!)

In any case, I have not changed any of our machines' default paths or environment variables. Instead, I have simply created an alias that points to Anaconda python: "apython"

Example:

Thus, Diego should now be able to complete his script that needs the newer Scipy, as well as CDSutils. 

Final note: I've tested z (read|write|avg) with $PATH modified to have /ligo/apps/anaconda/bin at the start, and they seem to work. If things seem to hold up, maybe we can replace the default command-line python, but its not strictly necessary. 

Given the checkout of the aLIGO BBPDs happening (aLOG link), wherein the PDs were acting funny, and Koji has made some measurements determining that intermodulation/nonlinearity of circuitry can corrupt 3F signals, I've made a similar measurement of the RF spectra of REFL165 when we're locked on DRMI using 1F signals. Maybe this could give us insight to our bad luck using REFL165...

In essence, I plugged the RF output of the PD into an AG4395, through a 10dB attenuator and downloaded the spectrum. I also did REFL33 as a possible comparison and because why not. The attached plots have the 10dB accounted for; the text files do not. 

REFL165 (Exposed PCB BBPD):

(What is all that crap between 8 and 9 fmod?)

REFL33 (Gold Box resonant RFPD):

If you look at the intermodulation at 14 (4+10) and 16 (6+10), 15 (5+10) would make any problem, thanks to the notch at 1f and 5f.

BUT, this absolute level of 165MHz is too tiny for the demodulator. From the level of the demodulated signal, I can say REFL165 has
too little SNR. We want to amplify it before the demodulator.

Can you measure this again with a directional coupler instead of the direct measurement with an attenuator?
The downstream has bunch of non-50Ohm components and may cause unknown effect on the tiny 165MHz signal.
We want to measure the spectrum as close situation as possible to the nominal configuration.

90MHz crap is the amplifier noise due to bad power bypassing or bad circuit shielding.

I have no comment on REFL33 as it has completely different amplification stages.

[Steve, Diego, Manasa]

Since the beatnotes have disappeared, I am taking this as a chance to put the FOL setup together hoping it might help us find them.

Two 70m long fibers now run along the length of the Y arm and reach the PSL table.

The fibers are running through armaflex insulating tubes on the cable racks. The excess length ~6m sits in its spool on the top of the PSL table enclosure.

Both the fibers were tested OK using the fiber fault locator. We had to remove the coupled end of the fiber from the mount and put it back in the process. So there is only 8mW of end laser power at the PSL table after this activity as opposed to ~13mW.  This will be recovered with some alignment tweaking.

After the activity I found that the ETMY wouldn't damp. I traced the problem to the ETMY SUS model not running in c1iscey. Restarting the models in c1iscey solved the problem.

Found the IR beatnote between PSL and Y end laser.

Since our goal was to find the beatnote ASAP to recover ALS, I ignored the fine details in alignment. I will revisit the setup to make some improvements in the near future.

1. Coupled the PSL IR beam leaking after the doubler into the fiber. We have only 10% coupling into the fiber at the PSL table right now (6mw); but this will be improved once I get a suitable translation stage for the telescope.

2. PSL IR --> PM980 fiber --->50-50 fiber beam splitter ---> 50-50 fiber beam combiner
  AUX Y ---> PM980 fiber ---> 50-50 fiber beam combiner
The output port of the fiber beam combiner is connected to the fiber coupled broadband RF PD.

3. The RF output of the PD when connected to a spectrum analyzer shows a beatnote of -50dBm. The small amplitude of the beatnote is due to the laser power being attenuated before coupling into the fiber to keep the PD safe.

Attached is photo of how the setup is put on the PSL table. We will put all the stuff in a box once the X setup is also in place.

Green beatnotes recovered.

It was just a matter of aligning the arm greens and PSL greens on the PSL table. I suppose something knocked the PSL alignment out of whack... I was also able to simultaneously see the green beatnote and IR beatnote respond to Yend laser temperature. 

Locked arms on POX/POY, checked RMS of ALS-BEAT[X/Y]_FINE_PHASE_OUT_HZ channels. 

• ALSY: 300Hz RMS
• ALSX: 700Hz RMS

These seem fine. Locked CARM and DARM on ALS, found IR resonances. 

ALS is back in business 

Now that I have followed the chain, the PD signal is indeed being amplified at the LSC rack. It goes into a ZFL-1000LN+ amplifier (~23dB gain at 165MHz and 15V supply), followed by a SHP-100 high pass filter, and then enters the RF IN of the demod board. 

I repeated the measurement in two spots.

First, I took a spectrum of the RF MON of the REFL165 demod board during DRMI lock; this was input-referred by adding 20dBm. 

Second, I inserted a ZFDC-10-5 coupler between the high pass and the RF input of the demod board. This was input-referred by adding 10dBm. 

My calibration isn't perfect; the peaks above the high pass corner seem to be different by a consistent amount, but within a few dBm. 

Thus, it looks like the demod board is getting a little under -40dBm of 165MHz signal at its input. 

 Tonight I tried some more tests on the script; it seems to work better, with both performance and robustness improved, although the Xarm behaved badly almost all the time. I did not perform all the tests I wanted because the ALS lock was pretty unstable tonight (not only because of the X arm), with more than a few lock losses; after the last lock loss, however, I couldn't restore the Xarm. I'll do some more tests as soon I can recover it, or post the result of the first batch of tests.

In addition, I encountered the following error multiple times, but I have no idea about what could it be:

Thu Nov 06 02:00:13 PST 2014
medmCAExceptionHandlerCb: Channel Access Exception:
Channel Name: Unavailable
Native Type: Unavailable
Native Count: 0
Access: Unavailable
IOC: Unavailable
Message: Virtual circuit disconnect
Context: fb.martian.113.168.192.in-addr.arpa:5064
Requested Type: TYPENOTCONN
Requested Count: 0
Source File: ../cac.cpp
Line number: 1214
 

Where is the PD out spectrum measured with the coupler???

EDIT on X arm: I found different settings in C1SUS_ITMX, with respect to ETMX, ITMY and ETMY (namely LSC/DAMP is OFF and LSC/BIAS is ON); I don't know if this is intended or for some reason ITMX was not recovered properly after the lock loss, so I didn't change anything, but it may be worth looking into that.

Still no luck in recovering the X arm, I am giving up for tonight; honestly I didn't try many things, as I don't know well the system and didn't want to mess things up.

Preliminary results so far:

I confirm that the best settings for the ramp of the ALS scan are 20s and 500 points; this causes however the script to be fairly slow (80s for the scan/data collection, 7s for the coarse peak finding, 17s for the fine peak finding, total ~2 min); in the best cases the TR*_OUT obtained is around 0.90, as shown in the first plot (early in the evening, all the following plots are in chronological order, if that can help finding the reason for the X arm misbehaviour...):

However, after a few minutes somehow the TR*_OUT went down a bit, without any kind of intervention; also, it is visible the instability of the X arm:

Even when X arm was somewhat stable, its performance and robustness were (far) worse than the Y arm ones:

The following plot shows (about the Y arm only) that there is still some margin, as the maximum value of TRY_OUT is not completely kept at the end of the procedure:

Finally the last plot I managed to obtain, before the X arm went completely crazy...

The next step, after obviously figuring out the X arm situation, is to try some averaging during the fine scan, I don' t know if this will improve the situation, however it shouldn't impact on the execution time. Tomorrow I'll post something more detailed on the script itself and the wavelet implementation.

 AP Armaflex  tube 7/8" ID X 1" wall insulation for the long fiber in wall mounted cable trays installed yesterday.

The 6 ft long sections are not glued. Cable tied into the tray pressed against one an other, so they are air tight. This will allow us adding more fibers later.

 Atm2: Fiber PSL ends  protection added on Friday.

Liyuan is measuring the He/Ne telescopes in the Y arm between the tube and CES wall. He'll be here till 1pm

 The "coupled" port of the coupler went to the AG4395 input, the output of the Highpass is connected to the "IN", and the "OUT" goes to the demod board. 

[Diego, Koji]

X arm has been restored, after modifying the two parameters mentioned in http://nodus.ligo.caltech.edu:8080/40m/10676 (C1SUS_ITMX:  LSC/DAMP and LSC/BIAS); after that, a manual re-alignment of ETMX was necessary due to heavy PIT misalignment. I will check the ALS lock once work on the Y arm is done.

IMC WFS operating point seemed to get degraded.

- IMC WFS feedback was relieved.

- WFS servo was turned off.

- IMC alignment was tuned carefully

- /opt/rtcds/caltech/c1/scripts/MC/WFS/WFS_FilterBank_offsets was run

- WFS servo was turned on again 

That's not what I'm asking.

Also additional cables are left connected to the signal path. I removed it.

After some enlightening conversation with Koji, we figured that the RF amplifier in the REFL165 chain is probably being saturated (the amp's 1dB compression is at +3dBm, has 23dB gain, and there are multiple lines above -20dBm coming out of the PD). I took a few more spectrum measurements to quantify the consequences, as well as a test with the highpass connected directly to the PD output, that should reduce the power into the amplifier. However, I am leaving everything hooked back up in its original state (and have removed all couplers and analyzers...)

I also took some DRMI sensing measurements. In the simple Michelson configuration, I took TFs of each ITMs motion to AS55Q to make sure the drives were well balanced. They were. Then, in the DRMI, I took swept sine TFs of PRCL, SRCL and differential ITM MICH motion to the Is and Qs of AS55 and all of the REFLs. I constrained the sweeps to 300Hz->2kHz; the loops have some amount of coupling so I wanted to stay out of their bandwidth. I also took a TF of the pure BS motion and BS-PRM MICH to the PDs. From these and future measurements, I hope to pursue better estimates of the sensing matrix elements of the DRMI DoFs, and perhaps the coefficients for compensating both SRCL and PRCL out of BS motion. 

I'm leaving analysis and interpretation for the daytime, and handing the IFO back to Diego...

 Liyuan is continuing his measurement in the Y arm till noon today.

The measurements I took yesterday bear this out. However, even putting the high-pass directly on the PD output doesn't reduce the signal enough to avoid saturating the amplifier.

We need to think of the right way to get the 165MHz signal at large enough, but undistorted, amplitude to the demod board. 

 The current signal chain looks like:

I previously made measurements at (3). Let's ignore that. 

Last night, I took measurements with a directional coupler at points (1) and (2), to see the signal levels before and after the amplifier. I divided the spectrum at (2) by the nominal gain of the amplifier, 23.5dB; thus if everything was linear, the spectra would be very similar. This is not the case, and it is evident why. There are multiple signals stronger than -20dBm, and the amplifier has a 1dB compression point of +3dBm, so any one of these lines at 4x, 6x and 10x fMod is enough to saturate. 

I also made a measurement at point 4 in the following arrangement, in an attempt to reduce the signal amplitude incident on the amplifier.  

 Though the signals below 100MHz are attenuated as expected, the signal at 110MHz is still too large for the amplifier. 

Minicircuits' SHP-150 only has 13dB suppression at 110MHz, which would not be enough either. SHP-175 has 31dB suppression at 110MHz and 0.82dB at 160MHz, maybe this is what we want.

I have found an SHP-150, but no SHP-175's (also, several 200's, and a couple of 500's).

Why do you say the SHP-150 isn't enough?  The blue peak at 10*fmod in your plot looks like it's at -12 dBm.  -13 dB on top of that will leave that peak at -25 dBm.  That should be enough to keep us from saturation, right?  It's not a lot of headroom, but we can give it a twirl until a 175-er comes in.  

Koji also suggests putting in a 110 MHz notch, combined with either an SHP-150 or SHP-175, although we'll have to measure the combined TF to make sure the notch doesn't spoil the high pass's response too much.

Yesterday I did some more tests with a modifies script; the main difference is that scipy's default wavelet implementation is quite rigid, and it allows only very few choices on the wavelet. The main issue is that our signal is a real, always positive symmetrical signal, while wavelets are defined as 0-integral functions, and can be both real or complex, depending on the wavelet; I found a different wavelet implementation, and I combined it with some modified code from the scipy source, in order to be able to select different wavelets. The result is the wavelet_custom.py module, which lives in the same ALS script directory and it is called by the script. In both the script and the module there the references I used while writing them. It is now possible to select almost any wavelet included in this custom module; "almost" means that the scipy code that calls the find_peaks_cwt routine is picky on the input parameters of the wavelet function, I may dig into that later. For the last tests, instead of using a Ricker wavelet (aka Mexican hat, or Derivative of Gaussian Order 2), I used a DOG(6), as it also has two lesser positive lobes, which can help in finding the resonance; the presence of negative lobes is, as I said, unavoidable. I attach an example of the wavelet forms that are possible, and in my opinion, excluding the asymmetric and/or complex ones, the DOG(6) seems the best choice, and it has provided slightly better results. There are other wavelet around, but they are not included in the module so I should implement them myself, I will first see if they seem fitting our case before starting writing them into the module. However, the problem of not finding the perfect working point (the "overshoot-like" plot in my previous elog) is not completely solved. Eric had a good idea about that: during the fine scan, the the PO*11_ERR_DQ signals should be in their linear range, so I could also use them and check their zero crossing to find the optimal working. I will be working on that.

 Avoid rabbit holes! What I did at LLO which works is to install an Anaconda in some shared directory and then just make an alias which puts that directory at the head of the path when running the more advanced SciPy installs. It works fine and cannot interfere with our usual operation since its only sourced when running peak find.

 I think 'saturation' here is a misleading term to think about. In the RF amplifiers, there is always saturation. What we're trying to minimize is the amount of distorted waveforms appearing at 3f and 15f from the other large peaks. Usually for saturation we are worried about how much the big peak is getting distorted; not the case for us.

PRM sus damping recovered and PMC locked.

 Jenne and I measured the situation using a SHP-150 directly attached to the REFL165 RF output, and at first glance, the magnitude of the 165MHz signal seems to not be distorted by the amplifier. 

We will soon investigate whether 165 signal quality has indeed improved. 

To further reduce the RF power at 110MHz in the REFL165 chain, I made a twin-t notch in a pomona box.

It is tuned at 110.66MHz.

The inductor is Coil Craft 5mm tunable (164-09A06SL 100-134nH).
Without the 10Ohm resister (like a usual notch), the dip was ~20dB. With this configuration, the notch of -42dB was realized.

Q >> Please measure the RF spectrum again with the notch.

I was able to lock the DRMI on 3f signals this evening, although the loops are not stable, and I can hear oscillations in the speakers.  I think the big key to making this work was the placement of the SHP-150 high pass filter at the REFL165 PD, and also the installation of Koji's 110 MHz notch filter just before the amplifier, which is before the demod board for REFL165.  These were done to prevent RF signal distortion.

DRMI 3f:   With DRMI locked on 1f (MICH gain = 1, PRCL gain = -0.05, SRCL gain = 2, MICH = 1*REFL55Q, PRCL = 0.1*REFL11I, SRCL = 1*REFL165I), I excited lines, and found the signs and values for 3f matrix elements.  I was using the same gains, but MICH = 0.5*REFL165Q, PRCL = 0.8*REFL33I and SRCL = -0.2*REFL165I.  Part of the problem is likely that I need to include off-diagonal elements in the input matrix to remove PRCL from the SRCL error signal. 

With the DRMI locked on 1f, I took a sensing matrix measurement.  I don't think we believe the W/ct of the photodiode calibration (we need to redo this), but otherwise the sensing matrix measurement should be accurate.  Since the calibration of the PDs isn't for sure, the relative magnitude for signals between PDs shouldn't be taken as gospel, but within a single PD they should be fine for comparison. 

As a side note, we weren't sure about the MICH -> ITMs balancing, so we checked during a MICH-only, and with the locking apparatus we are unable to measure a difference between 1's for both ITMs in the output matrix, and 1 for ITMX and 0.99 for ITMY.  So, we can't measure 1% misbalances in the actuator, but we think we're at least pretty close to driving pure MICH. 

We kind of expect that SRCL should only be present in the 55 and 165 PDs, although we see it strongly in all of the REFL PDs.  Also, PRCL and SRCL are not both lined up in the I-phase.  So, I invite other people to check what they think the sensing matrix looks like. 

• The excitation lines (and matching notches) were on from 12:14am (
• Nov 11 2014 08:14:00 UTC / GPS 1099728856) to 12:20am (
•  
• Nov 11 2014 08:20:00 UTC / GPS 
• 1099729216) for 360sec. 
• MICH was driven with 800 counts at 675.13 Hz, with +1*ITMY, -1*ITMX. 
• PRCL was driven with 1000 counts at 621.13 Hz with the PRM. 
• SRCL was driven with 800 counts at 585.13 Hz using the SRM. 

All 3 degrees of freedom have notches at all 3 of those frequencies in the FM10 of the filter banks (and they were all turned on).  During this time, DRMI was locked with 1f signals. 

DRMI sensing matrix:

Earlier in the evening, I also took a PRMI sensing matrix, with the PRMI locked on REFL33 I&Q.  Watch out for the different placement of the plots - I couldn't measure AS55 in the DRMI case, since cdsutils.avg freaked out if I asked for more than 14 numbers (#PDs * #dofs) at a time.

Rana, Koji and I were staring at the DRMI sensing matrix for a little while, and we aren't sure why PRCL and SRCL aren't co-aligned, and why they aren't orthogonal to MICH.  Do we think it's possible to do something to digitally realign them?  Will the solution that we choose be valid for many CARM offsets, or do we have to change things every few steps (which we don't want to do)? 

Things to work on:

* Reanalyze DRMI sensing matrix data from 12:14-12:20am. 

* Make a simulated scan of higher order mode resonances in the arm cavities.  Is it possible that on one or both sides of the CARM resonance we are getting HOM resonances of the sidebands? 

* Figure out how to make DRMI 3f loops stable.

* Try CARM offset reduction with DRMI, and / or PRMI on REFL 165.

The new nodus machine is being brought to life; until installation is finished and everything is fine, the old nodus will be unharmed. For future reference:

New Nodus hardware:

Case: SuperMicro SC825MTQ-R700U

M/B: SuperMicro X8DTU-F

CPU: 2x Intel Xeon X5650

RAM: 3x Kingston KVR1333D3S8R9S (2GB)

         3x Samsung M393B5673EH1-CH9 (2GB)

           Total 12 GB

HDD: Seagate ST3400832AS (400GB)

Current software situation and current issues :

1) Ubuntu Server 12.04.5 is installed and updated

2) The usual 'controls' user is present, with UID=1001 and GID=1001

3) Packages installed: nfs-common, rpcbind, ntp, dokuwiki, apache2, php5, openssh-server, elog-2.8.0-2 [from source], make, gcc, libssl-dev [dependencies for elog], subversion

4) Network: interface eth0 is set up (static IP and configuration in /etc/network/interfaces); eth1 is recognized and added, but not configured yet

5) DNS: configuration is in /etc/resolvconf/resolv.conf.d/base (since /etc/resolv.conf is overwritten by the resolvconf program using the 'base' database)

6) ntp is installed and (presumably) configured, but ntpd misbehaves (namely, all the servers are found, but a 

tail /var/log/syslog

shows that no actual synchronization is performed, and the daemon keeps

Listening on routing socket on fd #22 for interface updates

7) dokuwiki apache2 php subversion elog are installed but not configured yet (I need info about their current state, configuration and whereabouts)

8) I copied and merged the old nodus' .bashrc and .cshrc into new nodus' .bashrc, need to know if something has to be added

9) backup frames, backup user dirs and 40m public_html are not set yet, as in #7

Is there something missing?

If there is something missing from here (ligo/cds software, smartmontools/hddtemp and similar, or anything else) tell me and I'll set them up.

Sensing matrix calculation using DTT + Matlab

Note: If the signal phase is, for example,  '47 deg', the phase rotation angle is -47deg in order to bring this signal to 'I' phase.

Note2: As I didn't have the DQ channels for the actuation, only the relative signs between the PDs are used to produce the radar chart.
This means that it may contain 180deg uncertainty for a particular actuator. But this does not change the independence (or degeneracy) of the signals.


=== Sensing Matrix Report ===
Test time: 2014-11-11 08:14:00
Starting GPS Time: 1099728855.0
 

== PRCL ==
Actuation frequency: 621.13 Hz
Suspension (PRM) response at the act. freq.: 5.0803e-14/f^2 m/cnt
Actuation amplitude: 20.3948 cnt/rtHz
Actuation displacement: 1.0361e-12 m/rtHz
 
C1:LSC-AS55_I_ERR_DQ 4.20e+10
C1:LSC-AS55_Q_ERR_DQ -1.91e+11
==> AS55: 1.95e+11 [m/cnt] -24.58 [deg]
C1:LSC-REFL11_I_ERR_DQ 3.17e+12
C1:LSC-REFL11_Q_ERR_DQ -8.04e+10
==> REFL11: 3.17e+12 [m/cnt] -18.20 [deg]
C1:LSC-REFL33_I_ERR_DQ 4.15e+11
C1:LSC-REFL33_Q_ERR_DQ 4.28e+10
==> REFL33: 4.17e+11 [m/cnt] -137.11 [deg]
C1:LSC-REFL55_I_ERR_DQ 1.90e+10
C1:LSC-REFL55_Q_ERR_DQ -9.91e+09
==> REFL55: 2.14e+10 [m/cnt] -58.58 [deg]
C1:LSC-REFL165_I_ERR_DQ -1.16e+11
C1:LSC-REFL165_Q_ERR_DQ -3.14e+10
==> REFL165: 1.20e+11 [m/cnt] 45.20 [deg]
 
 
== MICH ==
Actuation frequency: 675.13 Hz
Suspension (ITMX) response at the act. freq.: 1.0312e-14/f^2 m/cnt
Suspension (ITMY) response at the act. freq.: 1.0224e-14/f^2 m/cnt
Actuation amplitude: 974.2957 cnt/rtHz
Actuation displacement (ITMX+ITMY): 2.0007e-11 m/rtHz
 
C1:LSC-AS55_I_ERR_DQ 2.55e+12
C1:LSC-AS55_Q_ERR_DQ 4.51e+12
==> AS55: 5.18e+12 [m/cnt] 113.51 [deg]
C1:LSC-REFL11_I_ERR_DQ -4.84e+10
C1:LSC-REFL11_Q_ERR_DQ -4.07e+09
==> REFL11: 4.85e+10 [m/cnt] 168.06 [deg]
C1:LSC-REFL33_I_ERR_DQ 2.06e+10
C1:LSC-REFL33_Q_ERR_DQ -9.39e+09
==> REFL33: 2.26e+10 [m/cnt] -167.51 [deg]
C1:LSC-REFL55_I_ERR_DQ 2.52e+09
C1:LSC-REFL55_Q_ERR_DQ -1.02e+10
==> REFL55: 1.05e+10 [m/cnt] -107.09 [deg]
C1:LSC-REFL165_I_ERR_DQ -1.79e+10
C1:LSC-REFL165_Q_ERR_DQ -5.50e+10
==> REFL165: 5.79e+10 [m/cnt] 102.02 [deg]


== SRCL ==
Actuation frequency: 585.13 Hz
Suspension (SRM) response at the act. freq.: 5.5494e-14/f^2 m/cnt
Actuation amplitude: 1176.3066 cnt/rtHz
Actuation displacement: 6.5278e-11 m/rtHz
 
C1:LSC-AS55_I_ERR_DQ -9.90e+10
C1:LSC-AS55_Q_ERR_DQ -1.18e+11
==> AS55: 1.54e+11 [m/cnt] -76.89 [deg]
C1:LSC-REFL11_I_ERR_DQ 2.96e+08
C1:LSC-REFL11_Q_ERR_DQ 4.78e+08
==> REFL11: 5.62e+08 [m/cnt] 41.42 [deg]
C1:LSC-REFL33_I_ERR_DQ -2.93e+09
C1:LSC-REFL33_Q_ERR_DQ 1.23e+10
==> REFL33: 1.27e+10 [m/cnt] -39.63 [deg]
C1:LSC-REFL55_I_ERR_DQ 3.71e+09
C1:LSC-REFL55_Q_ERR_DQ 2.78e+09
==> REFL55: 4.63e+09 [m/cnt] 5.86 [deg]
C1:LSC-REFL165_I_ERR_DQ -1.80e+10
C1:LSC-REFL165_Q_ERR_DQ 2.68e+10
==> REFL165: 3.23e+10 [m/cnt] -26.02 [deg]
 

Demodulation phases of the day

    'C1:LSC-AS55_PHASE_R = -53'
    'C1:LSC-REFL11_PHASE_R = 16.75'
    'C1:LSC-REFL33_PHASE_R = 143'
    'C1:LSC-REFL55_PHASE_R = 31'
    'C1:LSC-REFL165_PHASE_R = 150'


The notch filter has been installed directly attached to the output of the SHP-150 at the PD output. Structurally, there is a right angle SMA elbow between the two filters; I set up a post holder under the notch pomona box to prevent torque on the PD. Via directional coupler and AG4395, we measured the output of the REFL165 RF amplifier with the PRMI locked on REFL33. 

Note, the plot below is not referred to the amplifier output, as in my previous plots; it is directly representative of the amplifier output spectrum. 

There are no RF signals being output above -28dBm, thus I am confident that we are not subject to compression distortion. 

Given the last measurements we made (ELOG 10692), I estimate that the notch has reduced the power at 110MHz by ~33dB, which is 9dB higher than the notch performance Koji measured when he made it. Maybe this could be due to the non-50Ohm impedance of the HPF distorting the tuning, or I physically detuned it when mounting it on the PD. Still, 33dB is pretty good, and may even give us room to amplify further. (ZRL-700+ instead of the ZFL-1000LN+?)

I did some simulations to see if we are susceptible to HOM resonances as we reduce the CARM offset. I restricted my search to HG modes of the Carrier+[-55,-11,0,+11,+55]MHz fields with n+m<6, and used all the real physical parameters I could get ahold of. 

In short, as I change the CARM offset, I don't see any stray resonances within 2nm of zero, either in PRFPMI or DRFPMI. 

Now, the mode matching in my simulation is not the real mode matching our real interferometer has. Thus, it can't tell us how much power we may see in a given mode, but it can tell us about our susceptibility to different modes. I.e. if we were to have some power in a certain mode coming out of the IMC, or present in the vertex, we can see what it would do in the arms. 

Since my simulation has some random amounts of power in each HOM coming into the interferometer, I simply swept the CARM offset and looked for peaks in the power of each mode. Many of the fields exhibited gentle slopes over the range, and we know we ok from 3nm->~100pm, so I made the selection rule that a "peak" must be at least 10 times as big as the minimum value over the whole range, in order to see fields that really do have CARM dependence. 

In the following plots, normalized IFO power is plotted and the locations of HOM peaks are indicated with circles; their actual heights are arbitrary, since I don't know our real mode content. However, I'm not really too concerned, since all I see is some -11MHz modes between 2-3nm of full resonance, where we have no problem controlling things... Also, all of the carrier HOMs effectively co-resonate with the 00 mode, which isn't too surprising, and I didn't include these modes in the plots.

Finally, I visually inspected the traces for all of the modes, and didn't really find anything else peeking out. 

Code, plots attached.  

Koji pointed out something to me that I think he had told me ages ago, and Rana alluded to last night:  Since I'm not tuning my "demod phase" for the sensing matrix lockins, unless I happened to get very lucky, I was throwing away most of the signal.  Lame.  

So, now the magnitude is sqrt(real^2 + imag^2), where real and imag here are the I and Q outputs of the lockin demodulator, after the 0.1Hz lowpass.  (I put in the low pass into all of the Q filter banks).  To keep the signs consistent, I did do a rough tuning of those angles, so that I can use the sign of the real part as the sign of my signal.  When I was PRMI locked, I set the phase for all things acutated by MICH to be 79deg, all things actuated by PRCL to be 20 deg, and when DRMI locked set all things SRCL to be 50deg. 

After doing this, the phases of my sensing matrix output matches Koji's careful analyses.  I don't know where the W/ct numbers I was using came from (I don't think I made them up out of the blue, but I didn't document where they're from, so I need to remeasure them).  Anyhow, for now I have 1's in the calibration screen for the W/ct calibration for all PDs, so my sensing matrices are coming out in cts/m, which is the same unit that Koji's analysis is in. (Plot for comparing to Koji is at end of entry).

While reducing the CARM offset, I left the sensing matrix lines on, and watched how they evolved.  The phases don't seem to change all that much, but the magnitudes start to decrease as I increase the arm power.

For this screenshot, the left plot is the phases of the sensing matrix elements (all the REFL signals, MICH and PRCL), and the right plot is the magnitudes of those same elements.  Also plotted is the TRX power, as a proxy for CARM offset.  The y-scale for the TRX trace is 0-15.  The y-scale for all the phases is -360 to +360.  The y-scale of the magnitude traces are each one decade, on a log scale.

Bonus plot, same situation, but the next lock held for 20 minutes at arm powers of 8.  We don't know why we lost lock (none of the loops were oscillating, that I could see in the lockloss plot).

Here are some individual sensing matrix plots, for a single lock stretch, at various times.  One thing that you can see in the striptool screenshots that I don't know yet how to deal with for the radar plots is the error bars when the phase flips around by 360 degrees.  Anyhow, the errors in the phases certainly aren't as big as the error boxes make them look.

PRMI just locked, CARM offset about 3nm, CARM and DARM on ALS comm and diff, arm powers below 1:

PRMI still on REFL33 I&Q, CARM and DARM both on DC transmissions, arm powers about 4:

CARM offset reduced further, arm powers about 6:

CARM offset reduced even more, arm powers about 7:

For this plot for comparing with Koji's analysis, I had not yet put 1's in the calibration screen, so this is still in "W"/m, where "W" is meant to indicate that I don't really know the calibration at all.  What is good to see though is that the angles agree very well with Koji's analysis, even though he was analyzing data from yesterday, and this data was taken today.  This sensing matrix is DRMI-only (no arms), 1f locking.

Bonus plot, PRMI-only sensing matrix, with PRMI held using REFL 33 I&Q:

 I looked at the endtable for possible space to setup optics in order to couple the X end laser into a PM fiber.

Attached is the layout of where the setup will go and what are the existing stuff that will be moved.

In my previous meditations about RIN, particularly elog 10258, I was only thinking about the RIN contribution at the offset that I was currently sitting at.  Also, In elog 10258 I was comparing to the ALS signals and just said that the trans signals are better which is true, although isn't super helpful when thinking of reduced CARM offsets. 

My summary today is that I think we want to reduce the RIN in arm transmissions by a factor of 3.

Rather than dig around, I just remeasured the RIN, for both the single arm transmissions and the MC transmission.  (Data attached as .xml file)

The RMS RIN for the Xarm is 1.3e-2.  The RMS RIN for the Yarm is 8.9e-3.  The RMS RIN for MCtrans is 4.0e-3.  For the simulations below, I will use 1e-2 as an average RIN for the arms.

As an estimate of the RIN's contribution to cavity fluctuations, I divide the RIN by the slope of the CARM transmission peak.  The slope (from optickle) gives me [ delta-W / delta-m ], and the inverse of that gives me [ delta-m / delta-W ].  I multiply this by RIN, which is [ delta-W / W ] to get [delta-m / W]. 

Then, since I'm using the DC transmission signals as my error signals, I use just TRX (normalized to be 1 for single arm resonance) as my Watts.

So, in total, the traces plotted are { TRX * RIN / slope }. 

The 2 plots are the same data, one with linear-x and the other with log-x.  They both include my estimate of the cavity length fluctuations due to RIN at the arm transmission, as well as an estimate of the cavity length fluctuations if the arm RIN was as good as the MC RIN.  I also show the DRFPMI CARM linewidth (23 pm for HWHM), and 1% of that linewidth.  The last trace is 1% of the half-width of the transmission peak, at the current CARM offset.  For example, 1000 pm away from full resonance the half-width is 1000 pm and 1% of that is 10 pm. 

What we want to see here is that the solid blue line is below one of the dotted lines.  I think that using the overall linewidth (purple dotted line) isn't really the right thing to look at.  Our goal is to prevent excursions that will get too close to the resonance peak, and cause a lockloss.  A one picometer excursion is a much bigger problem (relatively) below say 100 pm, as opposed to above 100 pm.  So, I think that we should be looking at the half-width of the resonance peak at whatever the current CARM offset is (orange dotted line).  Above 25 pm, the blue line is below the orange line for all offsets plotted.  If we made the arm RIN as good as the MC RIN, that would be true down to 12-ish pm. 

We should be able to safely transition to non-normalized RF signals at 10pm or below.  This implies that (since any RF signals normalized by this RIN-y trans signal will have the RIN), we want to improve the RIN of the transmission PDs by about a factor of 3. (This will lower the blue line such that it crosses the orange dotted line at 10 pm).

MC WFS was oscillative at 1Hz. I've reduced the servo gain further (x1, x1, x10, x1, x1, and x10).

The MC mirrors were realigned, and the WFS offsets were reset.

So, with my last entry, I was guilty of just throwing stuff into the simulation and not thinking about physics... so I retreated to Siegman for some algebraic calculations of the additional Guoy phase accumulated by the HOMs in the arms -> their resonant frequencies -> the arm length offset where they should resonate. Really, this isn't completely precise, as I treated the arms independently, with slightly differing ETM radii of curvature, but I would expect the "CARM Arm" to behave as a sort of average of the two arm cavities in this regard. (EDIT: Also, I didn't really consider the effect of the coupled vertex cavities... so there's more to be done)

The basic idea I used was:

• Assume ITMs are effectively flat, infinite Rc
• Use 40mwiki values for ETM curvatures
• Each additional HG order adds arccos(sqrt(1 - Larm/Rc)) of Guoy phase for a one way trip down the cavity (Eqn 19.19 in Sigman)
• For each HOM order up to 5 of the carrier and first order sidebands, add the appropriate phase shift 
• fold it onto +-FSR/2 of the carrier 00 resonance, convert to m

In practice, I threw together a python script to do this all and print out a table. I've highlighted the values within 10nm, but the closet one is 3.8nm

Results:

 I modified the MC2 trans optical setup a little bit: the reflection from the QPD was not dumped and so it was hitting the wall of the black box.

I angled the QPD slightly and moved the dump so that the reflection hit it. The leakage through the 50/50 steering mirror for the QPD was already being dumped and I made sure that that one stayed dumped on its razor dump. After doing this we turned off the WFS and re-aligned the MC2 trans beam onto the QPD to zero the pit/yaw signals.