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Plan for the NIKA2 re-commissioning, after the March 2025 upgrade

See also the minutes of the 2025/01/24 meeting dedicated to the re-commissioning.

List of operations / observations for the NIKA2 recommissioning (2nd half of March 2025)

1. new sweep, closed window
   • already will show if any KID has enhanced noise (no info about dichroic)

2. check DAQ on sky, check traces: could already see if there are problems on some KIDs
   

   • noise properties also shows if dichroic is healthy source / beam width

- pointing, focus, pointing, beam-map

• this very first observations might be a bit tricky, because we likely do not have the possibility to alternate the new sweep to the old sweep (because we have completely new arrays), therefore the question is how we will assess the first data (pointing/focus). I asked Juan last week at the telescope, and there is a way to do it with the IDL pipeline.

- reduce quickly these data, derive quick rough DAFs and finally enable the

• PIIC monitor. This takes some time: transfer the data (by hand, without waiting for the Grenoble mirroring), and analyze them (takes few hours for the beam map). At the beginning one beam map might be enough. This process will need some back-forth iterations, between observations and data processing. This is not the on the fly data processing, therefore it takes more time

- any possible idle times could be filled by EMIR.

- determine / check the passbands with the PIMP

• who on site is able to run the PIMP

  documentation wiki NIKA2 -> PIMP is there special ini file for DAQ it will be craned it up to the cabin in advance analyse the data -> Juan

- see above (I will add later): small beam maps

- With beam maps we will assess the "flat field", i.e. we assess if the current

• shadowing caused by the dichroic is gone. We can also assess how big is the difference in beam shape/s (i.e. focus) across the f.o.v.

- with the focus maps + beam maps, we assess immediately how much is the focus difference

• between Ar. 1,2,3

- I'd say we need some statistics, therefore we will probably need one/two

• days/night of data (or are few scans enough?)

- then we can take a decision: does the upgraded NIKA2 need to be opened again,

• so to optimize the (relative) position of the three arrays and make so that they all three have the same focus? Are there any other issues that need to be solved by opening the cryostat?

- if so, then assess by how much the arrays need to be moved (and which arrays),

• open NIKA2 again and proceed. Finally close, cool down, and repeat the above listed operations. In order to do this efficiently, the people who can open the instrument should be on site, or in Granada, so that they can promptly intervene. If not, then we will observe with EMIR while waiting for them to come, or we keep observing with the upgraded, sub-optimal NIKA2, if the difference in focus between the arrays is not dramatic.

- if we decide to re-open, then no need for a pointing session

- we perform the full characterization of the arrays

• - 1h on HLS
  • first assessment of new sensitivity if good, then spend time on faint source
  - deep integration on faint source G2 (5-10 hours) - orion-B - M8182 - polarimetry QSOs - polarimetry Crab Nebula - beam map on 3C286 - beam map Uranus in pol-mode - calib_1scan on all possible calibrators - external calibrator on/off

- considering that the cool down takes ~1 week, it's necessary to take this decision

• quickly, either with IDL or PIIC, in order to have still time for further recommissioning after opening, changing, closing and re-cooling, within the two weeks that are available (March 18th to April 1st)

- if no second opening is necessary, then we proceed directly with the next steps.

- in this case, perform a pointing session too

- in this case, also de-focused beam maps

• - aim: determine the best offset to have the best focus on avg over the whole
  • focal surface (at the moment this is the "famous" 0.2 mm offset)

- once we have decided that the instrument is in its "final" hardware configuration,

• we proceed further with its characterization

- keep doing pointing, focus, beam maps. Add calib_1scan to determine the new

• absolute flux calibration factors

- derive the NEFD and update the exposure time calculator

- test polarimetry: again the usual series of scans (pointing, focus, calib_1scan,

• beam maps). The analysis of these takes longer and is not critical for setting up the instrument, therefore we can collect the data and process them a posteriori "at home". This will bring: evaluation of the instrumental pattern (is it better than before?); characterization of the pol. angle systematics, and maybe other issues.

- test the instrument on known targets/scans, in order to be able to compare with

• the performance before the upgrade: 2251+158; MWC349; Uranus.

- We then also need larger maps onto which we will evaluate the rms in typical condition.

• To this aim, we can use two total power targets: Orion-B (project 113-24 and previous submissions) and M8182 (used to test the new servo system in January 2024). Both are free from conflicts and both are big maps aimed at this purpose. They should be enough to cover a large LST range, complementing the polarimetry targets and others (to be decided).