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Contents

  1. NIKA2 Re-Commissioning (4th. attempt)
      1. NIKA2 run 75, Cryo run 87
    2. Oct. 13, 2025
    3. Oct. 14, 2025
      1. End of the day+night summary
      2. Tables (from 2025/10/14 ~13:00 UT to 2025/10/15 ~4:00 UT)
    4. Oct. 15, 2025
      1. Summary
      2. Tables (from 2025/10/15 ~04:00 UT to 2025/10/XX ~YY UT)

NIKA2 Re-Commissioning (4th. attempt)

NIKA2 run 75, Cryo run 87

Oct. 13, 2025

14:00-17:00; Martino, Alessandro, Dave, Angel: a new sweep was performed. Previous initialization file: run87_old.ini. Bad/total KIDs counts (cryo window closed) after sweep (Ar1, Ar2, Ar3): 9/1000, 8/574, 4/1013. New file in force: run87_new.ini. Files run87_new_tp.ini and run87_new_pol.ini were also created. See nika2-a:~/nika_V3_IRAM.ini.

Oct. 14, 2025

Angel, Miguel, Stefano, and maaaany others arrive at the telescope.

We rename the ini files:
run87.ini (active file)
run87_old.ini (OLD active file, not used in August)
run87_newSweep_tp.ini
run87_newSweep_pol.ini
run87_oldSweep_tp.ini
run87_oldSweep_pol.ini

@15:00 LT (13:00 UT) we start, after preparing the whole "NIKA2 week environment architecture: 15/8/55 lost KIDs in Ar 1,2,3. Unstable sky and thick clouds coming from the N. We're entering in the peak of the tau forecast. It will be better later this evening. Meanwhile we try to focus. The old make-imbf script does not produce the imbfits files. Angel contacts Albrecht to solve the issue. The new make-imbf produces the file regularly.

On the very variable thick clouds, we notice a very different response of Ar1 and Ar3 to sky noise (variations), the latter having a bkg few times higher than the former (compare the y-axis scales). Is it real? Is there a flux calibration problem in the old DAFs? The a posteriori (19:00 LT) check does not reveal any calibration issue: Ar1 and Ar3 give similar fluxes for the targeted sources.

Ar2 bad sky Ar1 bad sky Ar3 bad sky

While we wait, some checks to some Antenna temperature control cables are being carried out by the telescope team. We start again 18:45 LT. The old make-imbf is now producing files correctly (thanks Albrecht!).

We work on the focus. Here follow our observations/notes. It is hard to get the focus value for all three arrays at once. The Ar2 flux criterion shows big jumps. The Ar2 FWHM and flux criteria do not agree. It almost seems like the flux is maximized not when the FWHM is minimized. Strange behavious, almost as if there were more than one "best" focus position. We enlarge the focus range of the 5 scans sequence. It was +/- 0.8 mm in steps of 0.4 mm. Now we changed it to +/- 1.0 mm, in steps of 0.5mm. The aim is to see if we can have a more complete sampling of the focus curve (for all criteria). The new script is called focusOTF-Z_2025.pako. We also try with a total excursion of +/-1.2 mm and steps of 0.6 mm. It seems that this latter solution is the best.

Is it possible that the difference in focus between Ar2 and Ar1 is changing? The first time it was ~0.3 mm. The second time it was ~0.6 mm. Now it is ~1.0mm??? At the same time, the focus difference between Ar1 and Ar3 seems stable at ~0.2 mm. It's early to be worried, but let's keep an eye on this! Nope, using the +/-1.2 mm excursion, we get back to 0.6mm difference between Ar2 and Ar1. Fiuuuu.

We alternate pointing/focus obtained with the old sweep and beam maps taken with the new one. The goal is to have at least two beam maps per array, taken with the optimal focus for that same given array. In the tables below, we list: focus sequences, beam maps, calib_1scan, other relevant scans, and a book keeping of sweep changes (to be used when defining the new calibration files - PIIC DAFs, for example - for this recommissioning run).

End of the day+night summary

At the end of the day+night, we have:

In this way, we cover the whole range from Ar2-0.3 to Ar3+0.3 with 6 focus positions: Ar2-0.3, Ar2, Ar2+0.3, Ar1, Ar3, Ar3+0.3. It might turn out that we need more positions in order to determne well the three focal surfaces.

Note that the latter 2 items (in the list above) have been performed when the taumeter opacity started to increase. Nevertheless the l.o.s. peak-to-peak sky noise variations kept being ~1 Jy/beam the whole time. If these last three beam maps have issues, we'll need to perform a whole sequence of 6-7 beam-maps at different focal positions, during a very stable night, such that the reference focus does not vary across the sequence (it takes few hours, hence the very stable need.)

Impressions about the difference in focus of the three arrays. The focus difference between Ar2 and Ar1 seems to be between 0.6 and 0.7 mm. The focus difference between Ar1 and Ar3 seems to be further 0.2-0.3 mm. The total focus difference between Ar2 and Ar3 reaches up to 1.0 mm. A decent compromise might be to use the focus of Ar1 as reference, but a quantitative analysis is needed to say the last word.

Tables (from 2025/10/14 ~13:00 UT to 2025/10/15 ~4:00 UT)

Dinner Time at Pico Veleta...
Our friendly goat having dinner... Our friendly fox waiting for dinner... They're waiting for dinner too!
[ATTACH] Meet our new friend. Her name is Tau. She wants dinner too. And this is C/2025 R2 Swan... it's evidently dinner time up there too.

Oct. 15, 2025

Summary

HLS091828 Ar2 HLS091828 Ar1 HLS091828 Ar3

Tables (from 2025/10/15 ~04:00 UT to 2025/10/XX ~YY UT)