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NIKA2 Re-Commissioning

March 18th - 25th, 2025 + March 30th - April 1st, 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

There's a bit of snow...

In the morning we check the NIKA2 traces:

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

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.

Frederic checks the ice conditions

Wednesday, March 19th, 2025

Good morning!

@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.

Thursday, March 20th, 2025

Tonight it's windy 60 m/s!!! ...

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.

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. Outside temperature -6deg. De-icing at full power. Low lying clouds above the telescope. AB tested the new ini file for acquisition with pimp.

@10:00 LT: Dave arriving. NIKA2 cooling ok, though 1 fan is stopped due to a block of ice.

@12:30 LT: PIMP work started:

@13:00 LT SB and CK join the PIMP work and we all test it together:

Example of RFdIdQ vs. pimp_pos, one of the first tests done this morning. We were not aware of how to set the temperatures of the cold/hot loads properly, hence this was taken with both temperatures at ~19 C.
One of the frst interferograms

@14:30 LT: DJ & AB are working on exchanging the Ar3 synthesizer, but they interrupt because it requires more operations than expected.

@14:40 LT: we continue the PIMP work. Here follow a list of the important things we do and learn. This can be used as a "practical guide" to use the PIMP in the future, and a condensed shortlist has been copied to the dedicated PIMP IRAM-ES wiki page:

@16:00-17:00 LT we are almost ready to start the PIMP integrations. Only the hot load temperature needs to reach 110 C. Meanwhile we take some test scans, to verify that the files are now correctly written, using the manual procedure. And here start some problems:

@17:20 LT it's time to go on

Summary of scan file names (in the run84_X/X36_2025_03_21/ directory):

@17:55 LT: the NIKA2 window cover is back in place. We give it some time and then we'll check the tuning again, to see if the KIDs will be back. And @18:10 they're all back, all three Arrays, with lost KIDS: 11/13/11 (Ar1,2,3). It seems that the PIMP (hot) load was too hot (we used ~110 C as recommended).

We did not find the convergent lens.

Synthesizer exchanged. However, there is no effect on the power spectra.

Saturday, March 22nd, 2025

@09:40 LT: Stopped. blue sky, low wind. But there is a lot of ice in the dish and it is -10deg. Pointing towards the sun.

@10:00 LT: Changed back to old synthesizer. One of the two NIKA2 fans starts hitting ice. Difficult to access due to risk of ice fall.

@10:40 LT: PIMP restarted. Checking black-bodies temperature settings for the PIMP. Today we keep the hot load colder (~50 C) than yesterday (~110 C). DAQ restarted; bad KIDs: 70/953, 8/578, 24/1000 (look better than yesterday). Today's data are in the run84_X/X36_2025_03_22/ directory. Here's a summary of the scans we took:

One example of today's PIMP signal (RFdIdQ vs. pimp_pos):
Today's PIMP signal

@15:00 LT: after talking with Juan, we do it again, switching the auto-tune OFF! Nevertheless, we don't solve the problem of the "plateau" at the peak signal. It takes another 2 hours, with the online live support of Juan and Andrea, to figure it out. Basically, the problem was that the moving mirror was not going all the way to 78200 steps (39 mm) as designated, but it was stopping (and coming back) at 61000 (30 mm). The illuminating point was the suggetsion by Andrea and Juan to try to "go a bit further" or move the fixed mirror - or the polarizer - by at least ~1 cm. The solution was to change the frequency resolution from 5 GHz to 3.85 GHz. Therefore, now, the best set of parameters values is:

List of scans (run84_X/X36_2025_03_22/X_2025_03_22_*_AA_man )

The last scan (nr. 90) is a test to see the effect of the auto-tune switched ON. Result: on the Ar2 traces no obvious difference is seen with respect to the scans with the auto-tune switched OFF.

Examples for Ar2 vs sample (left) and vs pimp_pos (right):
Ar2 vs sample Ar2 vs pimp_pos

Example for Ar3 vs sample (left) and bonus image of today (right):
Ar3 vs sample Brrrrr... when is Spring coming?

Fast (and dirty) spectral analysis of scan 77
WD spectra BWD spectra

Sunday, March 23rd, 2025

@09:30 LT: Still stopped, like every other day since we arrived. Snowing, foggy, -7deg.

@11:00 LT: Angel found the convergent lens of the PIMP. It was located 2 m away from the PIMP box, in a bubble wrap, with no labels whatsoever, on top of a pile of random cartoon boxes. Perfect! Than you Angel for your sharp eye! Now we mount it and re-do the PIMP story once again with this convergent lens. Note that the divergent lens is much thicker at the edge than the convergent one, therefore the screws that hold it are too long for the convergent lens (SB: no comment). Dave retrieves shorted screws. We adopt the same parameters as yesterday (see above for details).

SB thanks personally Dave for spending the weekend with us in the snow storm(s), instead of enjoying a warm sunshine down in Granada.

List of scans (run84_X/X36_2025_03_23/X_2025_03_23_*_AA_man )

@ 13:00 LT: PIMP has been de-installed, packed, and craned down again. With some more experience, the PIMP page has been updated.

Craning down PIMP's wooden box and support

@ 17:00 LT: Still stopped: windy, foggy, snowing.

@ 19:45 LT: Before craning down the PIMP, Dave closed the NIKA2 window and shielded its borders with aluminum tape. Switched to run84_tp.ini file. DAQ restarted and re-tuned: 7/953, 16/578, 9/1000 KIDs lost (Ar1,2,3). Screenshots below show the monitor and bottom-line noise traces at this time:

monitor_20250323 noisetr_ar1_20250323 noisetr_ar2_20250323 noisetr_ar3_20250323

@21:30 LT: we start the new and old make-imbf, just in case there will be a chance to go on sky during the night (so we don't have to start it at 3 a.m.)

Monday, March 24th, 2025

@ 03:30 LT: Midnight snowfall was quite intense. Frédéric removed as much ice as he could from the legs and the sub-reflector cell. Thanks, Frédéric! But a couple of large ice sticks in the upper outer rim/layers on the lower part of M1 prevent the operations. Likewise, hard ice patches in the central part of M2 are also reported. The de-icing is still on, but the effect of the sun will be essential to have the telescope in good shape. Waiting for mid-morning.

@ 08:30 LT: Telescope oriented to the Sun position, 0 deg. elevation, for contributing to the de-icing. Switching off the telescope's de-icing system. Vertex cannot be opened (hinges are probably frozen).

@ 09:40 LT: After sunlight exposition, the telescope is under minimal conditions for starting observations (a thin layer of ice in the lower part of M1 remains at the beginning). Vertex opening system works properly. Moving the telescope close to 2251+158. DAQ restarted and re-tuned: 4/953, 16/578, 9/1000 KIDs lost. Nicolas Ponthieu joins us through skype. Adopting previous DAFs of array 2 for quick-look reduction using PIIC.

The first surprise of the morning was the absence of data from box C (array 2) after the first pointing and focus scans. See the results from PIIC and IDL for (e.g.) scan 20250324s35 in the screenshots below:

scan35_ar2_PIIC scan35_ar2_IDL

Several hypotheses are being managed. Firstly, DAQ was restarted twice and a hard reset of the Ar2 electronics was done. There is a suspicion that some KIDs of box C are noisier than expected, for any unknown reason so far. Stefano and Nicolas are editing the corresponding rejection thresholds -provisionally- in the KIDs signal in the PIIC and IDL-RTA codes, respectively, with the intention of recovering as many of them as possible in box C. Preliminary DAFs and KidPars are in progress.

Before the daily meeting, a partial beam map (scan 20250324s22; 25 scans) and two full beam maps (s23 and s37) were obtained, all of them on 2251+158. Beam shape was improving quickly since the beginning of the observations, getting a FWHM ~ 17.46" x 18.32" about 2.5 hours after the beginning of the observations.

@ 12:30 LT: Daily meeting (MR, SB, CK, DJ, IM, SA, SL, AS, AM, MS, AB). Updating about re-commissioning progress since last Friday. AM asked for obtaining some timelines for each array during scans on (e.g.) a planet.

@ 13:00 LT: Moving to Uranus when El. ~40 deg. From focus sequences, beam geometry is improving clearly. The screenshots below show the timelines of focus scans on Uranus per arrays 2 (box C), 1 and 3:

timelines_Uranus_ar2 timelines_Uranus_ar1 timelines_Uranus_ar3

Note by SL: For A2 it seems you have plotted KIDs from box C which has a problem as you mentioned previously, so this is not representative of how the signal is for the boxes which don't have problem... Could you display the timelines of another box?

Getting skydips (s44, s99) and a full beam map (on-focus) on Uranus (s58).

@ 14:35 LT: Starting a calib_1scan session: Uranus (s61), MWC349 (s68), CRL2688 (s69), NGC7027 (s70), W3OH (s82)

@ 16:00 LT: Becoming cloudy. Last pointing corrections tell us about possible anomalous refraction in the l.o.s. Inside the cloud at 16:10 (LT). Observations stopped.

@ 17:30 LT: quick update on the preparation of the PIIC DAFs by SB:

While processing the beam maps with PIIC, it happened that the "new" imbf have a number of record couples with the same time. Jean has been notified. Meanwhile the imbf produced by the old make-imbf are being used.

List of KIDs numbering correspondences:

KID-ID (NIKA2 run 72 .ini)

NAME

Array

PIIC (run 68 sweep)

PIIC (run 72 sweep)

NOtes

821

KC016

2

363

363

OLD reference KID

813

KC009

2

355

355

Temp used by Stefano but failed on Ar1 and Ar3 w/ segm. fault!

416

KB013

2

202

202

Temp used by Stefano

6083

KP004

3

520

425

Temp used by Nicolas

@ 18:35 LT: Resuming observations. DAQ restarted and re-tuned: 9/953, 13/578, 22/1000 KIDs lost.

The screenshots below show a new set of timelines from focus scans on Mars per arrays 2 (box B), 1 (box H), and 3 (box Q):

timelines3_Mars_ar2 timelines3_Mars_ar1 timelines3_Mars_ar3

@20:00 LT: the POLAMI group of Ivan Agudo takes over, for 4 hours of POLAMI observations,.

@20:30 LT: we welcome back our old good friends, the Spindle / Hexapod Errors.. this time with some extra twist that complicate the recovery (Frederic et al. are working on it). We did not miss you!

@22:00 LT: after fighting with Box C, NIKA2 and PIIC for the whole day, Stefano finally converges to a preliminary PIIC analysis of the beam-maps. Sorry for the delay: I re-did it N times, seeking different solutions for the reference KID and trying different tricks to solve the missing KID 363, but without success. Therefore now the preliminary version is based on KID 202 of Ar2 (see table above). The best beam map so far is scan 20250324s58, in my opinion. To be improved in the +/- near future with new data.

Here follow some plots that visualize the current status of the arrays, via the beam-maps analysis.

IDL results by Nicolas (thank you!), based on beam map 20250324s58:
IDL results on 20250324s58 IDL results on 20250324s58

PIIC results by Stefano, based on beam map 20250324s58:
PIIC results on 20250324s58, Ar2 PIIC results on 20250324s58, Ar2 PIIC results on 20250324s58, Ar2 PIIC results on 20250324s58, Ar2
PIIC results on 20250324s58, Ar1 PIIC results on 20250324s58, Ar1
PIIC results on 20250324s58, Ar3 PIIC results on 20250324s58, Ar3

Note that in the reduction/analysis of beam maps the Ar2 Box C is (much) more populated than in the on the fly reduction of pointing/focus/maps scans. This is because of different thresholds (values/types) adopted in the different kinds of data reduction. The reference KID (363 Ar2) is rejected by PIIC because of very low (bad) flat field correction and also because of very low correlation coefficient. This happens likely because of the enhanced noise of Ar2 Box C.

As a comparison, the flat fields given by Perotto et al. 2020 are shown here:

Flat fields from Perotto+2020

Moreover, when reducing the pointing/focus or calib_1scan maps on the fly with PIIC, we noticed that Ar2 Box C is rejected systematically, but when the noise of the timelines is very high, few KIDs of Box C are retained. This likely happens because the rejection is done based on the noise of the given KID vs. the median noise of the whole array. Here follows a couple of examples: scans 20250324s7 and s103 (focus the attention on the top-right panel).

PIIC example of noisy scan, keeping some of the Ar2 Box C KIDs PIIC example of noisy scan, keeping few of the Ar2 Box C KIDs

Despite the fact that the beams did not look so nice today (especially at 1mm, likely due to bad sky conditions, but we cannot exclude some bad optics effects at this stage), here come some focus statistics (20250324s...), to be taken with a lot of grains of salt (approximative values, plus some targets are intrinsically extended). [NOTE: I later added also the 2025/03/25 (better) scans.]

2025/03/24

2025/03/25

scans

target

Ar2

Ar1

Ar3

scans

target

Ar2

Ar1

Ar3

6-10

2251+158

bad

bad

bad

6-10

1253-055

1.30

1.28

1.55

11-15

2251+158

2.18

bad

bad

13-17

MWC349

1.32

1.30

1.60

16-20

2251+158

2.50

2.55

2.72

21-25

NGC7027

1.25

1.25

1.52

24-28

2251+158

2.00

-

2.20

28-32

K3-50A

1.34

1.29

1.64

29-33

2251+158

1.90

-

2.15

35-39

CRL2688

1.29

1.30

1.56

39-43

Uranus

1.35

-

-

42-46

MWC349

1.25

1.24

1.50

47-51

Uranus

1.10

-

-

49-53

CRL2688

1.28

1.30

>1.70

52-56

Uranus

1.10

-

-

56-60

NGC7027

1.40

1.35

>1.70

63-67

MWC349

0.80

0.83

0.95

63-67

K3-50A

1.30

1.33

1.53

72-76

W3OH

0.95

1.00

1.10

71-75

MWC349

1.36

1.45

1.75

77-81

W3OH

0.80

1.05

bad

78-82

CRL2688

1.35

1.41

>1.70

88-92

Uranus

1.20

-

-

85-89

NGC7027

1.47

1.53

>1.70

93-97

Uranus

1.25

-

-

92-96

MWC349

1.55

1.63

1.90

103-107

Mars

1.30

1.51

1.60

112-116

W3OH

bad

bad

bad

150-154

Mars

1.40

1.45

1.53

117-121

W3OH

1.25

1.26

1.49

156-160

Mars

1.30

1.30

1.50

Tuesday, March 25th, 2025

@00:00 LT: we restart the NIKA2 observations. Lost KIDs: 4/8/19

A nice example of focus (the best so far, scan 156):
PIIC Ar2 focus scans 156-160 PIIC Ar1 focus scans 156-160 PIIC Ar3 focus scans 156-160

@01:00 LT. Lost KIDs 15/11/54 on the DAQ

@01:20 LT we try to work on the electronics:

@03:20 Wonderful sky, we continue looping on pointing/focus/calibrators

@03:40 LT: Beammap on 1253-055 (scan 20250325s11). Very stable conditions: +-1Jy. tau225~0.23.

@04:40 LT: pointing, focus, calib_1scan on MWC349 (3 calib_1scans: 19,47,76), NGC7027 (3 calib_1scans; 26,61,90), K3-50A (2 calib_1scans; 33,69), CRL2688 (3 calib_1scans; 40,54,83).

@08:19 LT: Telescope alarm activated; hexapod error (Hxp limit XY triggered, according to the ACU prompter; it happens for the second time in ~12h as far as there is news). Stopped. Trying to recover the telescope. Enrique Lobato and Manuel Nieto (TG) are working on that.

@10:00 LT: After several tries, we continue with the problem. Trying again on W3OH. Pointing & focus okay. Then, a calib_1scan. Week finished.

@12:00-16:00 LT: Nicolas: Early analysis of March 24th and 25th focus sequences (IDL):

focus_3 focus_1 focus_2

The last plot shows the calib per kid mJy/Hz and the beam FWHM. No straightforward correlation between the central disk visible in calib and the beam FWHM. There's a hint of the same NW-SE band on A3 beam as on A2 calib...? True or fake? Could the dichroic explain this?

focus_3 focus_1 focus_2 focus_2

@14:39 LT: explanation of the noisier BOX C, by Alessandro and Dave:

Friday, March 28th, 2025

Angel, Dave and Stefano arrived again, safe, at the telescope.
Today is an EMIR day, but we came up early because there is no transport during the weekend.

@12:00 LT: Dave changed the (blue) polarisation box of channel 7 with a spare unit, but the ADC value of box C did not change.

@12:30 LT: we have our re-commissioning daily meeting:

@13:30 LT: Detailed plan, decided in the post-teleconf briefing here on site:

Good night!

Saturday, March 29th, 2025

We start the day with some "real astronomers" work...

Real astronomers at work! After a bit of stretch and unsharp masking Full view by Angel :-)

Africa and Gibraltar

Today was another EMIR day.

Sunday, March 30th, 2025

The NIKA2 operations are planned to start at 8:00 a.m. CEST. The daylight saving time started few hours ago.

@08:15 LT: we start the check of the radio alignment. Dave gradually slides a piece of absorber in front of the NIKA2 window and we check when the KIDs react. This is done from different directions. Then we change roles and do it again. The following table summarizes the measurements of the distance of the absorber from the opposit edge of the windown, when the KIDs react. The measurement has an uncertainty of 0.5 to 1.0 cm, related to several factors: delay in the response of the DAQ trace plot to the KIDs reaction; measurement with the extensible meter; absorber thickness; human hand; human eye; human reaction time to the plot of the DAQ; small number statistics. Note: the KIDs must be well tuned and need to be watching the sky. The diameter of the window is 23.5 cm. All measurements were performed checking the traces of Array 2.

Direction

measurement [cm]

u -> d

15.8-16.0

15.8

15.0-16.0

16.0

d -> u

15.5

16.0

15.0

15.0

r -> l

15.0-16.0

16.0

15.0-17.0

l -> r

15.0

15.0

15.5

45 deg 1

16.0

45 deg 2

15.0-15.5-15.8

45 deg 3

16

45 deg 4

14.5 difficult to assess

Direction

Average

r.m.s

u -> d

15.77

0.38

d -> u

15.38

0.48

r -> l

15.80

0.84

l -> r

15.17

0.29

Overall, the NIKA2 array(s) seem centered in the NIKA2 entrance window. The sensitive area is a square of side ~8.5 cm well centered. With this method we cannot get a better precision than +/- 0.5 at 1 sigma.

SL feedback (2025/03/31 in the afternoon): I'm surprised by your results, the sensitive area should have been much bigger than that. Unlike the measurements done in 2017 (see the History_of_optical_and_radio_alignments_of_NIKA2.pdf which is also available at the beginning of the "Commissioning & special test runs" section of the main wiki page), your measurement don't seem compatible with the expectations from optics simulations. Indeed as you can see on the figures below, in terms of rays tracing (left figure, showing the footprint of 10 beams from various point sources across the FOV) you should have a circular sensitive area (your 45 deg measurement actually go in that direction) of ~15.5 cm diameter, and in terms of physical optics propagation (POP) (right figure, showing the beam from a point source at the FOV center in a log-10 scale), which accounts for diffraction effects all along the optical chain, the sensitive area should even be a bit bigger, reaching almost 20 cm diameter. The POP figures illustrates why it is important to oversize the window with respect to the ray tracing: the goal is that the warm spillover diffracting on the window edge is far enough from the useful zone that only the 10-7 side lobe level reaches it and thus has a negligible contribution to the background. Note that with radio axis determination using the Eccosorb you shouldn't have the asymmetry visible on the POP figure; this asymmetry is only for beams coming from sky and is due to the off-axis reflections on M5 and M6, it fades away and on focal surfaces and become lower than 10-4, visible only beyond the 3rd diffraction ring.
Beam_on_window_Ray-trace_and_POP-f00

SB (2025/03/31): thank you for the feedback, Samuel. How would you then suggest to proceed?

@10:00 LT: we start the proper NIKA2 sky observations. Lost KIDs: 6/12/12. Box C is still noisy and therefore rejected. We use KID KB013 as reference (Ar2, see the numbering summary Table on Monday, 24th March). We start with several sequences of pointing, focus, calib_1scan on the usual suspects (MWC349, CR2688 and NGC7027), for few hours. For each source and cycle, we take calib_1scan focused on Ar2 and on Ar3.

2025/03/30 focus sequences

Scans

Target

Start El. [deg]

Ar2

Ar1

Ar3

Notes

78-82

3C345

47.2

1.0

1.1

1.5

Marginal for Ar3

85-89

MWC349

86.0

0.85

0.96

1.30

The new IMBF of scan 88 is missing

91-95

MWC349

84.5

0.83

0.93

1.15

Optimized for Ar3

106-110

MWC349

74.4

0.80

0.80

1.12

121-125

MWC349

65.1

0.70

0.75

1.05

The new IMBF of scan 124 is missing; Ar3 a bit marginal

134-138

MWC349

56.5

0.66

0.68

0.95

140

MWC349

53.9

n/a

n/a

n/a

Special "focustrack Z" scan (see below)

145-149

MWC349

49.5

0.51

0.57

0.80

160-164

MWC349

40.2

0.45

0.50

0.91

166

MWC349

37.5

n/a

n/a

n/a

Special "focustrack Z" scan

178-182

Uranus

64.6

0.51

0.62

0.93

184-188

Uranus

66.5

0.50

0.64

off

190

Uranus

68.3

-

-

-

please ignore this scan; Special "focustrack Z" scan

191-195

Uranus

68.6

-

-

-

please ignore this sequence

203-207

Uranus

71.6

0.31

0.37

0.64

209

Uranus

70.9

n/a

n/a

n/a

Special "focustrack Z" scan

212-216

Uranus

70.0

0.34

0.40

0.66

218

Uranus

68.7

n/a

n/a

n/a

Special "focustrack Z" scan

221-225

Uranus

67.2

0.62

0.67

off

227

Uranus

65.5

n/a

n/a

n/a

Special "focustrack Z" scan

228-232

Uranus

65.3

0.67

0.73

0.94

Optimized for Ar3

238-242

Uranus

59.8

0.70

0.76

1.00

248-252

Mars

62.9

0.76

0.79

1.06

258-262

Mars

69.0

0.68

0.72

0.95

264

Mars

71.3

n/a

n/a

n/a

Special "focustrack Z" scan

270-274

3C84

47.2

0.62

0.70

0.90

277

3C84

44.1

n/a

n/a

n/a

Special "focustrack Z" scan

283-287

3C84

29.6

1.20

1.25

1.47

289

3C84

27.4

n/a

n/a

n/a

Special "focustrack Z" scan

294-298

1253-055 (3C279)

34.9

1.45

1.50

1.61

(almost) one-sided A3 focus curve

300

1253-055 (3C279)

37.3

n/a

n/a

n/a

Special "focustrack Z" scan

303-307

1253-055 (3C279)

41.8

1.47

1.47

1.78

(almost) one-sided A3 focus curve

308-312

1253-055 (3C279)

43.0

1.45

1.47

1.71

well-sampled A3, A1 and A2 focus curves

Focus results for the days 24, 25 and 30 March, as derived by the PIIC monitor. Dashed lines: median values per day. Solid lines: median over the three days.
Focus values derived by the PIIC monitor Focus differences

Special, extra scans/data:

@14:45 (LT): the beam geometry looks distorted from pointing (MWC349, scan 165) after focus sequence. FWHM (a2, a1, a3): 17.9x19.3 arcsec; 12.2x15.9 arcsec; 11.5x21.8 arcsec.

@15:40 (LT): The telescope is suffering from the Sun illumination, combined to today's air temperature (+6 C). Moving to Uranus.

@18:30 LT: the main dish starts to relax

@19:00 LT: box P is missing (Ar3). We need to re-tune, after the focus s238-242 sequence. Lost KIDs 4/11/14 (Ar 1,2,3)

@19:30 LT: Uranus is at the same Az of the Sun. We move away and go to Mars.

The thin Moon says goodnight to Granada

@21:00 LT: after sunset, while waiting for the main dish to relax and reach the typical NIKA2 night focus, we observe the big M81-82 maps, monitoring the focus in between repetitions.

CK: Two quick comments: is Box P of Ar3 missing all the time ? Is this a big worry ? The z-Focus of Ar2 may be biased by the missing box C, as already pointed out by Nico. We'll need to be careful when deriving conclusions.

SB: quick answers: 1) no, Box P was easily recovered by re-tuning. 2) might be, but as long as the source is fully sampled by the map (which is the case, because the "holes" are elsewhere, and because we've chosen a reference KID that is not in Box C), I think we're safe.

CK: Does this mean that the z-focus currently measured with Ar2 will not be different from what we will measure with Box C repaired ?

SB: I don't fully understand how the missing Box C can change the focus. I think there will be no significant difference. Simply the S/N will be sqrt(25%) larger.

CK: The z-focus changes with radial distance from the central pixel. As box C mainly samples the inner part of the full 2mm array, those focus values are now missing.

SB: yes, the absolute value depends on the position on the array, but the optimal focus position is defined on a relative (between different subreflector's Z positions) basis and probably won't change much, because the distance of the current "ref pix" from the optical axis is of the order of 1-2 beams only.

Monday, March 31st, 2025

@00:30 LT: Last focus sequence (20250330s294-298), returned focus very close to the value expected for relaxed surface (1.5mm), see above table. Also Ar2 and Ar1 beams are much more symmetrical after adjusting the focus (17.4"x18.1" and 11.7"x13.7", respectively), while Ar3 remains elongated when optimizing the focus for Ar1/2, indicating again the focus discrepancy between Ar1/2 and Ar3. Sky is very stable, with +/- 0.5 Jy/beam at 2mm. So, I decide to do the first beam map on 1253-055/3C279 (20250330s301), with a focus position optimized for Ar1/2 (1.45 mm).

@01:30 LT: After verifying the optimal focus positions for Ar1/2 and Ar3 and confirming they remain stable, I continue with a beam map on 1253-055/3C279 (20250330s314), with a focus position optimized for Ar3 (1.71 mm).

@02:20 LT: Optimal focus positions remain stable. Beam maps on 1253-055/3C279, with a focus position optimized for Ar2 + 0.25 mm (1.7 mm, 20250331s8), Ar2 - 0.25 mm (1.2 mm, 20250331s10), Ar2 + 0.5 mm (1.95 mm, 20250331s12), Ar2 - 0.5 mm (0.95 mm, 20250331s14).

Summary of total power beam maps

Scan

Target

Focus [mm]

Notes

20250330s301

3C279

1.45

Optimized for Ar2

20250330s314

3C279

1.71

Optimized for Ar3

20250331s8

3C279

1.70

Ar2 focus +0.25 mm

20250331s10

3C279

1.20

Ar2 focus -0.25 mm

20250331s12

3C279

1.95

Ar2 focus +0.5 mm

20250331s14

3C279

0.95

Ar2 focus -0.5 mm

@05:00 LT: Checked focus again on 3C279 after the finish of the focused/defocused beam maps sequence. Generally fairly consistent with latest values, only a possible small discrepancy of about 0.1 mm wrt to the previous optimal focus value (1.36 in Ar1/2 and 1.59 for Ar3).

2025/03/31 focus sequences

Scans

Target

Start El. [deg]

Ar2

Ar1

Ar3

Notes

1-5

1253-055 (3C279)

46.4

1.46

1.47

1.73

well-sampled A3, A1 and A2 focus curves

7

1253-055 (3C279)

46.9

n/a

n/a

n/a

Special "focustrack Z" scan

16-20

1253-055 (3C279)

36.1

1.36

1.36

1.59

well-sampled A3, A1 and A2 focus curves

22

1253-055 (3C279)

34.1

n/a

n/a

n/a

Special "focustrack Z" scan

25-29

1253-055 (3C279)

28.2

1.25

1.26

1.50

NIKA2-Pol mode, partially sampled Ar3 focus curve

30-34

1253-055 (3C279)

26.4

1.21

1.25

1.44

NIKA2-Pol mode

57-61

1641+399 (3C345)

70.5

1.44

1.50

1.87

NIKA2-Pol mode; repeating to have better Ar3-focus fitting

62-66

1641+399 (3C345)

68.4

1.46

1.51

1.74

NIKA2-Pol mode

68

1641+399 (3C345)

65.6

n/a

n/a

n/a

NIKA2-Pol mode; Special "focustrack Z" scan

77-81

1641+399 (3C345)

49.5

1.00

1.09

1.30

NIKA2-Pol mode

83

1641+399 (3C345)

47.3

n/a

n/a

n/a

NIKA2-Pol mode; Special "focustrack Z" scan

91-95

MWC349

75.9

0.22

0.26

0.60

NIKA2-Total power

118-122

MWC349

52.5

0.10

0.17

0.49

NIKA2-Total power

124

MWC349

49.9

n/a

n/a

n/a

Special "focustrack Z" scan

131-135

MWC349

43.2

0.27

0.33

0.65

Ar3 marginal

137

MWC349

41.3

n/a

n/a

n/a

Special "focustrack Z" scan

144-148

3C454

49.8

0.47

0.53

0.80

Ar3 marginal

160-164

3C454

32.6

0.65

0.68

>0.9

Ar3 terrible

183-187

3C84

37.8

1.51

1.58

1.80

197-201

Mars

60.2

1.44

1.55

>1.80

Ar3 bad

202-206

Mars

58.4

1.40

1.45

1.70

208

Mars

56.2

n/a

n/a

n/a

Special "focustrack Z" scan

@05:20 LT: Start with NIKA2-Pol mode. Tuning fine (lost KIDs 9/10/26) and HWP behavior normal. Start with pointing and focus on 1253-055 (3C279). Then calib_1scan on the same target with focus optimized for Ar1/2 (1.21 mm, 20250331s36) and then for Ar3 (1.44 mm, 20250331s37). Moving quickly to 1226+023 (3C273; also close to El. 20) an getting a calib_1scan with both focus optimizations (1.21 mm, 20250331s39; 1.44 mm, 20250331s40).

@06:40 LT: Continuing on 1228+126 (M87), close to the previous targets (El. ~25 deg.); pointing (quite stable atmosphere) and calib_1scan with focus optimized for Ar1/2 (1.21 mm, 20250331s43) and for Ar3 (1.44 mm, 20250331s44) after that.

@06:54 LT: Changing to 1308+326 (El. ~40 deg.) It's time for observing without/with the external calibrator. Pointing first, beam sizes: 17.5"x18.1" (Ar2); 11.6"x12.2" (Ar1), 10.9"x13.7" (Ar3). No need to focus.

@07:24 LT: External calibrator switched off. Jumping to 3C286 (close to 1308+326). Calib_1scan with focus optimized for Ar1/2 (1.21 mm, 20250331s50); FWHM 17.4"x18.4". Then, a calib_1scan for Ar3 (1.44 mm, 20250331s51).

@07:35 LT: Pointing on 1510-089. Calib_1scan with focus optimized for Ar1/2 (1.21 mm, 20250331s53) and calib_1scan for Ar3 (1.44 mm, 20250331s54).

@07:55 LT: A clear dawn. Stable atmosphere, no wind; tau ~0.14. Pointing on 1641+399 (3C345), El. ~70 deg. Getting a good focus (see table above). After focus correction, from pointing: FWHMs 16.8"x17.6" (Ar2), 10.9"x11.4" (Ar1), 11.1"x12.9" (Ar3). Special "focustrackZ" scan done (20250331s68). First sunbeams on telescope's backside @08:35 (LT). A second round of calibrations without/with the external calibrator:

@08:58 LT: After pointing on 3C345 (FWHM 17.1"x17.9", Ar2), we launched a beam map-pol (@202503/beammap1scan95sub_polar_hwp3hz_29min; 20250331s74). Unable to have the new imbfits for the beam map and the folllowing pointing scan (20250331s75). Service restarted and pointing relaunched (scan 76) for checking: everything is okay again.

@09:48 LT: Refocusing on 3C345 (see above). The beam for Ar2 looks a bit broadened (FWHM 18"x18.8"). A new round of calib_1scans with focii optimized and without/with the external calibrator:

@10:30 LT: We switch back to total power. After removing the HWP and switching the DAQ on again, Box D is not tuning properly. Dave goes in the cabin to put the NIKA2 window cover on for a while and see if Box D recovers. He'll also check that there is no hydraulics pipe (e.g. of the HWP movement) in the optical path (SB remembers that it happened months ago, maybe one year). We'll wait the time necessary for this check.

@11:10 LT: Instrument capabilities restored (thanks Dave!) after restarting the DAQ with the window closed. DAQ restarted successfully. Bad KIDs (a1, 2, 3): 4, 10, 16. Moving to MWC349. Focus corrections changed a lot (e.g. from 1.0 to 0.2 mm for Ar2; see the table above), despite M1 is not exposed to the Sun. But the day is clear, ambient temp. reaches 10C and rising, no wind. FWHM (Ar2) from pointing: 17.8"x18.8". Calib_1scan with focus optimized for Ar1/2 (0.18 mm, 20250331s103) and for Ar3 (0.51 mm, 20250331s104) after that. We did the same for NGC7027 (scans 20250331s106 ansd s107) and CRL2688 (scans s108 and s109). After a pointing (FWHM 17.9"18.8" for Ar2; no need to focus), we cycled the calib_1scans on this fantastic trio.

@12:30 LT we have our daily NIKA2 re-commissioning meeting:

@15:30 LT: after few more cycles of calibrations and focus sequences, we swicth to a carefully selected field aimed at checking the noise level in a map with several scans.

@17:30 LT: Samuel has written his feedback about the radio alignment check. See above here at the beginning of yesterday's report, when we described the results. His comments are in line with what we suspected and we wrote today in the summary of the daily meeting @12:30 LT. Thank you, Samuel. How would you then suggest to proceed? We still have some time today to try again, if needed.

@18:10 LT: we go to the cabin to repeat the radio alignment check. We find the culprit of the incorrect reslts of yesterday morning: we were simply not monitoring the proper KIDs. Yesterday we monitored a random box of Ar2, while the echoabsorber was introduced in the optical path. Today we realized that we should instead monitor the edge KIDs. This is obvious, but also not so obvious. Lesson learned: if you wanna do somebody's else job, insist to get some good fn instructions, otherwise you'll have to discover yourself how to do it. Same as March 21st-23rd. ROFLWP.

The external KIDs that we use today are marked in the following plot (PIIC numbering). The Table below summarizes our measurements and reports also the correspondance of the KIDs numbering. The measurements are taken from the position at which the KID starts reacting to the opposite edge of the NIKA2 window. Finally, we include also some photos taken during the operations (both yesterday and today). We end the new radio alignment check at ~19:45.

Ar2 KIDs used to check the radio alignment

The echo-absorber enters the optical path Measuring the distance Today's new setup The signatures of the echo-absorber on KID KC016

Measurements using KIDs at the edge

Direction

KID nr

KID ID

Measurements

Avg

rms

Top to Bottom

541

KD043

19.0 20.5 21.0 20.5 21.0

20.40

0.83

Bottom to Top

53

KA045

23.0 22.0 22.0 22.5 22.0

22.30

0.45

Right to Left

237

KB039

20.5 20.0 20.5 21.0 20.5

20.50

0.35

Left to Right

668

KD155

21.2 21.5 21.0 21.3 21.0

21.20

0.21

Measurements using the reference KID (nr 363, KC016)

Direction

Measurement

Avg

rms

Top to Bottom

18.0 17.2 16.8 17.0 16.8

17.16

0.50

Bottom to Top

17.5 16.8 17.8 18.0 17.5

17.52

0.46

Right to Left

17.5 17.8 17.5 17.8 17.5

17.62

0.16

Left to Right

18.0 17.5 17.8 17.5 17.5

17.66

0.23

Result: the radio alignment check reveals some not perfect centering, with an apparent shift to the bottom-left. I'm not sure whether this is significant of not, given the uncertainties. Here follows a scheme of Stefano's mesmerizing calculations (sorry, I'm too lazy to make a proper plot).

Scheme of radio alignment check results

@21:20 LT: Resuming observations. DAQ restated in total power; bad KIDs (a1, 2, 3): 8,11,16. Weird fittings after the first focus try. Guess value: 2 mm. Moving to 3C84. Best focus corrections given in the table above. Calib_1scan on Uranus, focus optimized for ar1/2 (1.51 mm; scan 20250331s189) and then optimized for ar3 (1.8 mm; 20250331s190). After pointing on 0716+714 (FWHM ar2, 1, 3: 16.6"x17.1", 10.9"x11.5", 10.7"x13.5"), we launched 1 repetition on M8182.

The ongoing observations... Grand finale Good night! See you next time!

Tuesday, April 1st, 2025

@00:00 LT: Checked again focus with Mars. Seems consistent with last correction. Best focus corrections given in the table above. After pointing again on 0716+714 (FWHM ar2, 1, 3: 17.1"x17.7", 11.4"x11.6", 11.0"x13.2"), launched 2 more repetitions on M8182.

@02:30 LT: Quicklook with PIIC not working due to date limitation of CAL files. SB becomes available (thanks!) and fixes the issue by extending the date range until June 1st, 2025. New setup tested with pointing, focus and calib_1scan scans successfully.

@03:30 LT: weather starts to degrade, tau225 steadily increasing from 0.1 to 0.3. Focus position changed by -0.3 mm.

@04:00 LT: Focus gets stabilized and started 1 rep on G2. Towards the end of the repetition, weather degraded even more.

2025/04/01 focus sequences

Scans

Target

Start El. [deg]

Ar2

Ar1

Ar3

Notes

6-10

0851+202

27.1

1.06

1.13

1.38

focus changed significantly

11-15

0851+202

25.0

1.17

1.22

>1.5

Ar3 bad

16-20

0851+202

22.7

1.08

1.16

1.38

22

0851+202

19.8

n/a

n/a

n/a

Special "focustrack Z" scan

35-39

1253-055

30.4

1.11

1.12

1.40

41

1253-055

28.2

n/a

n/a

n/a

Special "focustrack Z" scan

71-75

MWC349

72.5

1.50

>1.3

>1.7

Ar3 too bad, 1 imbfits missing (scan 72)

76-80

MWC349

74.4

1.35

1.42

1.66

82

MWC349

76.9

n/a

n/a

n/a

Special "focustrack Z" scan

@06:00 LT: Light haze, tau ~0.35. High background rms (>~300 mJy) in the ql maps at 1 mm. Moving to the main group of secondary flux calibrators. Pointing on MWC349. No need to focus again: FWHM 17.3"x17.9" (ar2). Getting calib_1scan maps with both focus optimizations (1.11 mm for Ar1/2 and 1.40 mm for Ar3): MWC349, NGC7027, CRL2688 (scans 20230401s47 to s52). Then, a skydip (20250401s53).

@07:20 LT: 3 reps. x 4 PA (10 x 5 sq.-arcmin maps) on Arp 220 (pointing on 1611+343 before and after such scans).

@08:30 LT: Coming back to the secondary flux calibrators. Sky's grayish. Pointing and focus on MWC349. Final results are given in the table above. Launching a new set of calib_1scan maps with two focus optimizations (1.35 mm for Ar1/2 and 1.66 mm for Ar3): MWC349, NGC7027, CRL2688 (scans 20230401s83 to s88). A skydip after that (20250104s89).

@10:00 LT: we switch off and say goodbye.

DailyReportsNika2Run72 (last edited 2025-04-01 13:32:16 by NikaBolometer)