Figure 1. Around 16 UTC there hase been a temporary decrease in BNS range by 15 Mpc for a couple of hours, it did not correspond to any obvious change in interferometer alignment.

Figure 2. At that time the noise on the B1 photodiode null channel (different between PDs) has increased. 

Figure 3. There is not a clear difference in behaviour between the two photodiodes. So it is not the case that one of the two photodiodes is failing. 

What is happening with the photodiodes needs to be understood. If it is a particular type of environmental noise coupling into the new PD design, or if there is some malfunction that affects both photodiodes, but not in the same way so that it shows both in the signal sum and in the difference (NULL channel).

ITF found in Science mode; it kept Science mode for all the shift.

Software

TCSMoni restarted at 11:18 UTC to take into account new configurations provided by experts.

Below are the useful time windows for analysis (all times in UTC on October 7th), selected to avoid, as much as possible, noise from maintenance activities:

• Quiet:  02:00:00 + 600s

• Step 1: 07:49:00 + 300s

• Step 3: 08:18:00 + 120s

• Step 5: 08:30:45 + 120s

• Step 7: 09:04:05 + 120s

The BaDAQ server has been restored by Otger.

As a consequence, the previous actions were reversed 

As data collection of the IMC baffle made by the BaDAQ server has not  been restored  since the end of June 2025 (see the plot) :

• it has been set as optional in the VPM configuration
• it has been removed from the list of expected sources at the FbmAlp server level 
  • this server provides a channel related to  the latency of each source  called  Daq_FbmAlp_<source_name>_latency
  • when an input source is missing it latency channel is set to 0.

21:00 UTC ITF found in SCIENCE. It kept the lock through the whole shift

Guard Tours (UTC)
- 21:26
23:13 - 23:50
01:10 - 01:47
03:12 - 03:50

Today, starting in the morning we dismounted the IPATSiA setup from WE and brought it to TCS room in the central building. We tested the picomotors and discovered that the picomotor of the horizontal DoF of the last mirror (that points towards the payload) is not working (so it has to be moved by hand).

In the afternoon,we started the shift by ending the installation of the setup around the WI tower. However, we had some problems related both to the cabling of the sensors and the chiller used (the TCS spare, stored in the TCS chiller room).

At first, we couldn't get the temperature probe working (it seems related to the module ENV-TCSR2, to be investigated). We then decided to continue checking only the power, but unfortunately the chiller used could barely reduce the T of the water by 0.5 degree in ~1h.

To avoid any damage to the laser, we only used it for small period, checking the alignement towards the mirror. We moved by hand the picomotors in order to put the CO2-PA into the center of the mirror.

We ended the shift at around 18:20 in order to have the time to relock.

To be noted: when trying to get IPATSiA working, i.e. with us close to the tower, the ITF kept unlocking sistematically, that even if we weren't moving. We should understand wether this is a problem related to the several devices switched on or only to the human presence.

Different interventions were performed during today's maintenance.

• Timing_DSP:
  Underthreshold values were observed for Sc_SR and Sc_NI.
  By rebooting the Sc_SR master board, we successfully resynchronized the DSPs with the GPS time.
  The same procedure was applied to the Sc_NI master board; however, in this case, it was necessary to manually upload the hrd file, as data were not available after the reboot.
  However, the timing issue still remains on Sc_NI and should be investigated jointly with DAQ team. 

• WI, NI, PR vertical accelerometers centering:
  The positions of the WI, NI and PR vertical accelerometers sensing elements were re-centered with motors

ITF found in LOW_NOISE_3 and in Science Mode wIth Autoscience On.

All times are UTC.

MAINTENANCE Mode set at 6:00. Activity during maintenance:
- Cleaning standard tour + FCIM and FCEM (Ciardelli/Menzione);
- 6:23 TCS Chiller refil (Ciardelli/Menzione);
- From 6:25 to 6:36 OMC Lock (Operator);
- From 6:40 to 7:02 OMC Scan (Operator);
- From 6:36 Excavator started working on flags basement;
- 7:09 ISC_Fb TolmFrameBuilder, see #67875 (Masserot);
- From 7:19 to 7:36 SR DSP Timing Issue (Palaia, Piendibene);
- From 7:13 to 9:26 INJ HVAC Injections, see #67876 (Soldani, Paoletti);
- 7:40 bashrc_Virgo, see #67878 (Carbognani, Seder);
- From 7:49 to 8:12 TCS Camera Reference (Operator);
- From 8:40 to 9:03TCS CO2 Power Check (Operator);
- From 8:53 to 9:45 NI DSP Timing Issue (Palaia, Piendibene);
- 9:33 TCS NI CO2 CH power adjustment (Cifaldi);
MAINTENANCE ended at 10:30.
EARTHQUAKE Mode set at 12:13,
EARTHQUAKE Mode ended and Autoscience engaged at 12:41.
ITF left in LOCKING_OMC_DARM_B1_PD3 with OMC unable to lock;

TCS CO2 Power Checks:

Due to a change in the AC setpoint caused by the recent hardware replacement (see entry #67766), NI and PR filter temperatures were out of range. Since CEB temperature is now stable, DMS thresholds have been updated accordingly.

Today we tested some settings of the INJ HVAC system, in order to evaluate the noise increase inside the INJ lab.

This is the timetable (UTC) of the operations:

• 07:39:40 Set to "person present in lab" mode (leave all systems in automatic mode)
• 07:56:00 Switch back to "no one in lab" mode – 15 min
• 08:10:30 Keep extraction (return air) flow rate constant + increase supply air fan to 33 Hz
• 08:20:30 Keep extraction flow rate constant + return supply air fan to baseline value (~23 Hz)
• 08:30:20 Keep supply air flow rate constant + increase extraction fan to 30 Hz
• 08:45:20 Keep supply air flow rate constant + return extraction fan to baseline value (~20 Hz)
• 08:56:30 Increase both supply and extraction fan frequencies simultaneously by 10 Hz
• 09:10:30 Restore all parameters to initial conditions – end of test

A detailed analysis will follow.

It is worth noting that some acoustic noise was detected inside the INJ lab by the microphones. This could be a consequence of the maintenance operations carried out on the platform inside the CEB.

Also note that during the automatic setting at 07:39:40 UTC, only the supply fan was adjusted by the system.

Here the computation of the angular noise budget computed with the injections done on 29 September: all couplings look higher than in the recent past, especially DIFFp (both) and PR_TX, which looks impacting at low frequency. To be noted that this measurement was done before the recent PR MAR rebalancing.

As trial to reduce the SUSP_Fb input data flow,  this morning the data related to the TCS_ADC_Moni1 ADC7674 are now sent ot the ISC_rtpc instead of the SUSP_rtpc

• operation performed at 2025-10-07-07h09m53-UTC

ITF found in ACQUIRE_LOW_NOISE_3 and in Prepare_Science Mode. Back in Science Mode from 21:07 UTC.
It unlocked at 0:59 UTC, back in Science Mode from 1:43 UTC.
ITF left locked.

13:00 UTC ITF found in SCIENCE
13:16 UTC Etalon corrections reset
13:17 UTC ITF in SCIENCE
13:45 UTC EGO truck passage near CEB
15:30 UTC ITF in COMMISSIONING
15:34 UTC inject_lsc.py started
15:36 UTC data loss (SUSP_Fb). Injections stopped
15:41 UTC injections restarted (ended 15:57 UTC)
16:00 UTC ITF in CALIBRATION (measurements with ITF unlocked)
16:03 UTC CALIBRATED_DELAY (ended 16:18 UTC)
16:21 UTC CALIBRATED_PRWI (ended 19.03 UTC)
17:14 UTC while executing READY_DF_INtoEND_LN, signal from LSC_B7_DC was a flat line and NARM_LOCK showed usermsg "Waiting for arm power estimation". Contacted ISC on call expert, NE/NI mirrors had rotated when CALI node was put in DOWN up to a point that NARM was completely misaligned. Once realigned, ITF was kept in LOCKED_ARMS_IR for a few minutes to stabilize, as instructed by the expert.
17:45 UTC started again READY_DF_INtoEND_LN. Couldn't achieve the state and LN1 in time to run CALIBRATED_DF_INtoEND_LN - Measurement of actuators response for NI,WI mirrors skipped
18:24 UTC seismic noise on B4, B7 and B8, seismon flag red, locking attempt failed. B1p_QD1 and B1p_QD2 galvo loops opened and were closed
19:12 UTC ITF in SCIENCE
19:34 UTC unlock, followed by unlocks at CARM_NULL_1F and LOCKING_CARM_NULL_3F (three times), B1p_QD1/2 Vbias rearmed
 

Guard Tours (UTC)
17:52 - 18:30
20:54 -

ISC
(06-10-2025 19:02 - 06-10-2025 19:40) From remote
Status: Ended
Description: NARM misalignment during calibrations, multiple unlocks
Actions undertaken: NARM showing no triggers (WARM showing no problems) after CALIBRATED_PRWI. Realigned

The unlocks between CARM_OFFSET_STEP_3_OF_3 and CARM_NULL_3F, at UTC 20:01:16, 20:10:44, 20:19:49 all look the same (Fig.1).

PRCL, MICH, SRCL and several AA loops experience a very fast oscillation (400 Hz), further modulated by another one at 60 Hz over a few tenths of a second. The same oscillation is visible on the Z correction of the IMC.

Considering that these are rather anomalous frequencies for ISC loops, the IMC control might be the cause.

I was called because the North arm was too misaligned to show flashes.

I corrected the alignment of the test masses and re-locked the arm.

This morning the ITF unlocked at 10:14UTC, it relocked at the first attempt (science started at 11:03UTC); science mode stopped from 9:14UTC to 9:15UTC for adjusting (tune etalon stet point).

ISC
- 9:14UTC: NI etalon set from 20.4 to 20.2, 86400 sec ramp time.
- 9:14UTC: WI etalon set from 20.8 to 20.63, 86400 sec ramp time.

ITF found in LOW_NOISE_3 and in Science Mode. ITF left locked.

Guard Tour (UTC)
22:05 - 22:41 
0:38 - 1:03
3:08 - 3:42 

DAQ
At 1:11 UTC the value of Hrec_Range_BNS jumped to 0 for around a minute due to missing data of SUSP_Fb.

13:00 UTC ITF found in SCIENCE, range oscillating between 8 and 50 Mpc, wind activity and sea activity flags red
13:16 UTC unlock, seimson flag also red.
13:38 UTC ITF set in BAD_WEATHER
17:41 UTC ITF in SCIENCE
19:35 UTC unlock (no ENV flags red), unsuccessful relock at LOCKING_CARM_NULL_3F twice
20:47 UTC ITF in SCIENCE

Guard Tours (UTC)
13:06 - 13:34
15:51 - 16:24
19:45 - 20:25

Air Conditioning
(05-10-2025 15:30 - 05-10-2025 17:20) On site
Status: Ended
Description: NEB air compressor 1 malfunction (see attached screenshot)
Actions undertaken: Entry 67865: Status of air comp 2 granted to be able to carry on through the night, air comp 1 broken and leaking oil was safely shut down, technician to be called tomorrow (Romboli)

Figure 1. The etalon control actuation has been saturating for the past 10 days for WI and past few days for NI. This is most likely due to the temperature in the CEB, that was decreased by ~1 degree by the change in temperature controller, and in addition to the decrease in outdoor temperature.

At the earliest occasion the temperature of both and WI and NI etalon set point should be reduced by one fringe for each of them to cope with the lower ambient temperature.

The following report has been submitted to the On-call interface.

On-call events -> Air Conditioning

Title: NE air compressor failure

Author(s): romboli

Details:

I received a call from the operator regarding a drop in air pressure at the NE. I consulted with D. Soldani and we verified that even if one compressor was broken, the compressed air should be supplied by the twin compressor, even though the alarm flag indicated only one of the two compressors. I arrived on site and indeed, one of the two compressors was out of power and had a significant oil leak. I took steps to shut it down, disconnect it from the air circuit, and verify that the twin compressor was working properly. The technician will be called immediately tomorrow morning to repair it.

* Note that any files attached to this report are available in the On-call interface.