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NIKA2 Re-Commissioning

March 18th-25th, 2025 + ...

NIKA2 run 72
Cryo run 84

Tuesday, March 18th, 2025

@10:30 a.m. Angel, Carsten, Monica, Stefano and maaany others arrived at the Telescope. There is a lot of snow 2-3m or more, accumulated by the wind in some spots), the windows of the dining room are completely covered. The sky is cloudy, but it seems that it might clear up a bit later. No precipitation at the moment

In the morning we check the NIKA2 traces:

• Ar1 looks fine.
• Ar3 has a big noise bump at ~0.3 Hz, common to all KIDs
• Ar2 has noisy KIDS in Box C. There is also a noise peak at ~10 Hz for a number of KIDs and a new spike at 6 Hz for KID KA156.

We have a briefing to make the point of what needs to be done first.

• the make-imbf is ready to be started and used. Both new and old versions are set to the current commissioning run
• New sweep: done on Wed 12/3. Ar1 OK. Ar3 noise bump. A second sweep was done on Fri 14/3, adjusting the Ar3 one. It looks better. Ar2 has the original sweep, defined in October 2024.
• Radio alignment check. the weather is not good enough. Maybe on Thursday we will have a chance. At the beginning we will start the operations without checking the alignment. Meanwhile we'll ask Dave if he'd be available on Thursday.
• check DAQ on sky. This is the first operation we will do:
  • Point a bright source (Mars, a QSO, or else, depending on the time of the day) and start an OTF
  • Check traces to verify that we see the source
  • check also the beam width on the traces

  • this will already tell us if a) we are on source; b) there are any problems with the dichroic and the beam

• small beam map: we will observe a small beam map (script already prepared by Nicolas and Angel), to be used by Nicolas to produce preliminary KIDPARS for the IDL pipeline
• with this, Nicolas will produce the first Kidpars.
• meanwhile we might observe already a first standard beam map for preliminary PIIC DAFs
• once the preliminary KIDPARS are ready, we proceed with pointing, focus, standard beam map, to be used to produce KIDPARS and DAFs for the whole array(s)
• with the big (standard) beam maps, Stefano will produce preliminary DAFs and Nicolas the KIDPARS
• once they're ready, we can start the PIIC Ql and we can give some peaceful time to Nicolas
• the standard beam map will give us already the followingnpieces of information:
  • DAFs/KIDPARS
  • flat field (i.e. is the dichroic healthy?)
  • focus difference between the three arrays
• we'll then loop on pointing, focus, primary calibrators and calib_1scan, with the aim to collect enough statistics for:
  • determine the new absolute flux calibration factors
  • study the difference of focus between the three arrays
  • derive new P2 and P7 values for the pointing model (Manuel might help with this)

We decide also that if we have dead times, there's no problem: we will avoid to put ourselves under pressure/stress and we will take the needed time to tackle possible problems/mistakes, discuss ideas and analyze the situation.

@13:15 LT: De-icing is switched on full power, but it's not fully working, there's some ice on the dish.

@15:25 LT: the Ar3 bump moved from 0.3 Hz to 0.6 Hz

@17:20 LT: it's still slightly snowing. Sometimes we see blu patches of sky. We check the main dish: it's mostly clean, except the upper-right rim and one of the four sub-reflectors supports. We park the antenna facing the "faint" sun, hoping it helps.

@19:00-19:30 LT: Frederic went up on the platform, but the ice on the legs of the subreflector is too hard and too far away to be reached and removed. Therefore we need to wait for the Sun to melt it tomorrow morning. Meanwhile the sky cleared up. Current air temperature: -4 C. Later the sky got foggy again.

Wednesday, March 19th, 2025

@07:00 LT: We wake up with a wonderful clear sky... and wind at 20-25 m/s. The current air temperture is -6 C. The telescope is facing the rising sun, in the hope that the ice melts, but the wind forecast predicts even stronger winds later today.

@10:00 LT: The wind has surpassed 32 m/s some time ago and some clouds are coming.

@12:30 LT: we have our first daily meeting.

• The weather is not collaborating, but we might have a chance tomorrow in the late morning and/or afternoon. Stay tuned!
• We developed a bad weather plan, in case we cannot go on the sky:
  • PIMP: craning it up, installing it, running it. Samuel will send info on how to install it with photos. Dave will come to the telescope on Thursday and Friday to help with all steps.
  • checks of the Ar3 synthetizer, Dave suggests to possibly replace it.
  • Dave suggests tests of the radio alignment, even against a closed vertex.
• Since the Ar3 noise bump at 0.3-0.6 Hz is happening with the closed NIKA2 window, we think that it must be something vibrating inside the instrument or something about the Ar3 synthetiser, which may be much more sensitive than the previous Ar3. It could be the wind, though the previous Ar3 did not show this. In any case, this low frequency correlated noise should not affect observations.

• Samuel points out that the constraints he set earlier for the check of the radio alignment (tau<0.2 and stability +/ 2 Jy/beam) can be relaxed. A tau up to 0.4 is fine, as long as we have stability.

• Samuel also suggests that - if we need to focus before the preliminary KIDPARS are ready - we could try to do it checking the traces and maximizing the signal of the source in there.
• priorities for tomorrow:
  • if the weather permits, the 1st priority is go on sky
  • if not, then we'll proceed with Dave's bad weather plan (see above)
• next meeting: tomorrow at 12:30 LT, using the IRAM-Granada video-cons system (check your email inbox)

Thursday, March 20th, 2025

During the night, we enjoy the wind show...

@08:00 LT: Current conditions: Temperature 0 C; wind speed ~20-30 m/s; sky partially cloudy. We now wait patiently for the wind to slow down further and give us a chance to start the NIKA2 operations.

@12:00 LT: Wind stays at 30-35 m/s. Transport cancelled. Based on input from SL, dedicated PIMP page created.

@12:30 LT: we have our daily meeting.

• observations cannot be started

• the transport up here has been cancelled because the wind is >35 m/s

• tomorrow Dave will likely come up
• the plan is to use the PIMP tomorrow
• Samuel prepared a very good collection of all available pieces of information about how to install and operate the PIMP (thank you! See above). We'll try our best, but we won't get crazy to figure it out, in case we can't make it work in few hours.
• Angel will write to Martino, Alessandro, Juan et al. with some questions about PIMP details and with the current PIMP .ini file for verification.
• a big wind and snow storm are expected for tonight.
• therefore we cancel the next daily meetings. If we need help for the PIMP, we will actively contact you again.

Friday, March 21st, 2025

@09:00 LT: stopped. Wind meter frozen, but wind is probably still around 20 m/s. There is a lot of ice at the subreflector and in the lower part of the dish. De-icing at full power. Low lying clouds above the telescope.