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| * Thanks to Brisa and the heterodyne pool week Team for this opportunity. |
Back to the NIKA2 Run 80 main page
Contents
-
Run80 data processing
- Focus difference between the three arrays
- Beam maps analysis
- Study of the Ar1 and Ar2 beams at different focus values
- New Study of the Ar1, Ar3 and Ar2 beams at different Z focus values
- Third (and last attempt to study of the Ar1, Ar3 and Ar2 beams at different Z focus values
- Test of focus difference between the three arrays after cryostat warm-up and cool-down cycle (April 25, 2026)
- A new test of focus difference between the arrays: May 19, 2026
Run80 data processing
Contributions by: Stefano Berta, Kaiyi Du.
Here we include the preliminary data reduction results of the re-commissioning NIKA2 run 80, as obtained at the telescope during this week (2026/03/24-31).
Focus difference between the three arrays
As of 2026/03/25 @01:25 UT.
The focus difference Ar1-Ar2 is roughly +1.00 mm.
The focus difference Ar3-Ar1 is roughly -0.05 mm.
Focus sequences
Scan nr
Target
Ar2
Ar1
Ar3
Polarized?
Notes
20260324s153-157
Uranus
0.27
1.25
1.2
no
Started at 1.0 mm; tadadada; Ar2 good fit; Ar1 and Ar3 fit is marginal
158-162
Uranus
out
1.3
1.25
no
Started at 1.5 mm; Ar1 perfect fit; Ar2 out of range
163-167
Uranus
0.28
out
out
no
Started at 0.5 mm; Ar2 perfect fit; Ar1 out of range
171-175
Uranus
out
1.22
1.18
no
started at 1.5 mm; Ar1 perfect fit; Ar2 out of range
206-210
0851+202
out
1.36
1.31
no
Started at 1.4 mm; Ar1 and Ar3 perfect fit; Ar2 out of range
Beam maps analysis
We have a new Ar3 and we need to characterize its geometry and its flat field. To this aim, on 2026/03/24 we took two beam maps focused on Ar1 (scans 20260324s169 and 177). The idea and hope is that the focus of Ar3 is roughly the same of that of Ar1, thanks to the March 10 intervention, and these beam maps will be good for our purpose.
We reduce the beam maps during the night between 2026/03/24 and 25.
Ar2 is out of focus and in order to be able to reduce it, we need to relax completely the constraints on its beam size and shape.
Ar1 is well on focus. The best beam map is 177. The other (169) has some problems at the lower edge for unknown reasons.
The Ar3 focus is decent. The array is missing Box S, as already known, and also several KIDs in Boxes M, N O (supposedly).
Below here you can see the geometry of the three Arrays as derived from the average of these two beam maps.
Study of the Ar1 and Ar2 beams at different focus values
On 2026/03/25, we carried out a series of calib_1scan with different focus values, starting from the Ar1 optimal focus to the Ar2 optimal focus, in steps of 0.2 mm. The aim was to study the change of MB flux (because the CAL is based on main beams), % of flux in the side lobes of the beam, and FWHM of the minor/major axes of the beam, as a function of focus (distance from the optimal position). Below here you find a table that summarizes our measurements and a series of plots produced by the PIIC monitors for Ar1 and Ar2.
Note, however that polarimetry observations would at best be carried out at the Ar1+3 optimal focus (rather than at a compromise focus) because of the criticality of the IP correction.
Studying this table, we have the suspicion that we need to perform a new lateral focus (XY). We are considering to postpone it to Sep-Oct, after a possible new NIKA2 hardware intervention.
Study of the NIKA2 beams (TP, point-like target)
General
Ar1
Ar2
Scan nr
El. [deg]
Target
Z Focus [mm]
Notes
MB flux [mJy]
Side lobes %
FWHM min [arcsec]
FWHM max [arcsec]
MB flux [mJy]
Side lobes %
FWHM min [arcsec]
FWHM max [arcsec]
243
48.8
3C273
1.35
Ar1 focus
4.85
7.4%
11.40
11.86
6.96
8.5%
17.72
20.47
245
50.1
3C273
1.15
Ar1-0.2 mm
4.32
9.5%
11.43
12.84
7.19
7.7%
17.54
19.49
247
51.8
3C273
0.95
Ar1-0.4 mm
4.07
11.2%
11.61
13.06
7.21
7.8%
17.24
19.60
249
52.9
3C273
0.75
Ar1-0.6 mm
3.77
16.0%
12.44
15.67
7.51
7.2%
17.19
18.84
251
53.7
3C273
0.55
Ar1-0.8 mm
3.62
19.8%
14.78
21.86
7.47
7.3%
17.34
18.56
253
54.3
3C273
0.35
+/- Ar2 focus
3.64
28.1%
17.40
29.17
7.34
8.0%
17.59
18.59
NOTE: the focus values listed here do already include the -0.2 adjustment for the curved focal surfaces
New Study of the Ar1, Ar3 and Ar2 beams at different Z focus values
2026/03/28-29 Following the request by Carsten, we repeat the experiment. Carsten noted that the best Ar2 beam is not at the best Ar2 focus, but a bit far from it. Several factors might be causing this:
- first of all this seems to be an indication of the need of a new lateral (XY) focus. We have discussed it here and we have decided to wait for October, because a) there won;t be any science observations meanwhile; b) there will hopefully be another NIKA2 hardare intervention to fix the difference of focus between Ar13 and Ar2, that seems to be caused again by the dichroic that is bending (a lot).
- during the whole campaign the best Z focus might have slightly changed, because of a change of Elevation and of other conditions such as temperature etc., although such change is surely not as big at 0.6 mm.
Check the table below: the Ar1 and Ar3 MB fluxes increase when they should be decreasing! Are we seeing the QSO that is bursting? Or is it the wind? Or the change of Elevation (I hope not!)
Study of the NIKA2 beams (TP, point-like target) using calib_1scan
General
Ar2
Ar1
Ar3
Extras
Scan nr
El. [deg]
Target
Z Focus [mm]
Notes
MB flux [mJy]
Side lobes %
FWHM min [arcsec]
FWHM max [arcsec]
MB flux [mJy]
Side lobes %
FWHM min [arcsec]
FWHM max [arcsec]
MB flux [mJy]
Side lobes %
FWHM min [arcsec]
FWHM max [arcsec]
windy records
20260328s165
38.9
3C279
1.59
Ar1 focus
12.34
9.4%
17.35
24.72
8.51
6.3%
11.52
12.10
11.32
7.5%
11.37
12.29
--
167
40.6
3C279
1.49
Ar1-0.1 mm windy
12.32
9.8%
17.25
25.01
8.17
6.5%
11.82
13.64
10.79
7.8%
11.78
13.23
5.5%
169
41.9
3C279
1.39
Ar1-0.2 mm windy
12.77
9.5%
17.03
25.02
8.39
7.1%
11.85
13.44
10.96
7.9%
11.73
13.07
8.9%
171
43.1
3C279
1.39 !
Ar1-0.3 mm windy
14.78
9.6%
16.81
25.82
10.98 (?)
7.8%
11.80
14.06
14.23 (?)
8.2%
11.84
13.52
9.0%
173
44.2
3C279
1.29
Ar1-0.4 mm windy
16.27
10.8%
17.71
26.68 (?)
14.18
9.2%
12.61
17.07
17.56
9.2%
12.63
16.49
7.5%
175
45.2
3C279
1.19
Ar1-0.5 mm
17.18
9.3%
17.31
24.85
14.83
8.4%
11.62
17.56
18.45
8.8%
11.80
16.16
--
177
45.9
3C279
1.59 !
Ar1 focus !
16.7
11.2%
17.05
29.45
15.56
9.1%
12.82
13.64
18.75
8.4%
12.31
13.55
--
20260329s2
46.4
3C279
1.09
Ar1-0.6 mm
18.12
10.3%
17.85
25.41
17.26
10.7%
11.86
21.65
20.12
10.4%
11.96
18.95
--
4
3C279
1.59 !
Ar1 focus ! windy
17.50
13.6%
17.46
34.04
17.19
13.2%
13.92
15.56
19.85
11.9%
12.90
15.72
14.7%
This last scan would have been on ar1 focus! We stop. Too much wind. We will have to repeat this exercise on a calm night, possibly wher the source is culminating, so to minimize the changes of Elevation between scans.
6 n/a
3C279
0.99
Ar1-0.7 mm
8 n/a
3C279
0.89
Ar1-0.8 mm
10 n/a
3C279
0.79
Ar1-0.9 mm
12 n/a
3C279
0.69
Ar2 focus
14 n/a
3C279
0.59
Ar2 focus
16 n/a
3C279
0.59
Ar2 focus
NOTE 1: the focus values listed here do already include the -0.2 adjustment for the curved focal surfaces
NOTE 2: the Ar3 absolute flux calibration is incorrect because no DAFs CAL are available yet
NOTE 3: focus performed in scans 159-163, Ar1=1.59; Ar3=1.54; Ar2=0.59
NOTE 4: windy records = percenteage of records rejected because of too large tracking deviations
Third (and last attempt to study of the Ar1, Ar3 and Ar2 beams at different Z focus values
2026/03/30 I try again. The wind has decreased significantly. This time I use 3C273 (much more stable than 3C279). I do it close to culmination, such that the change of Elevation is minimized. I also monitor the P100 information, i.e. the behaviour of the main dish / back structure temperature sensors. In fact, it is known that these sensors suffer humidity and condensation of the water that accumulates into the back structure. When they "get wet", the temperature difference in the back structure has some peaks and the temperature compensation of the focus goes bananas.
The procedure is as in the two previous attempts:
- pointing, focus, to determine the best focus values
- pointing, calib_1sca
- starting at the Ar1 focus and decresing to the Ar2 focus, in steps of 0.2 mm (as on 2026/03/25; instead of 0.1 mm as yesterday)
Study of the NIKA2 beams (TP, point-like target) using calib_1scan
General
Ar2
Ar1
Ar3
Scan nr
Tapas El. [deg]
Target
Z Focus [mm]
Notes
windy records
T diff bck struc [C]
T diff quadripod [C]
Z axis corr by T [um]
MB flux [mJy]
Side lobes %
FWHM min [arcsec]
FWHM max [arcsec]
MB flux [mJy]
Side lobes %
FWHM min [arcsec]
FWHM max [arcsec]
MB flux [mJy]
Side lobes %
FWHM min [arcsec]
FWHM max [arcsec]
20260330s11
54.01
3C273
1.05
Ar1 focus
--
-1.35
-0.41
-1063
7.02
12.8%
18.07
26.48
5.38
7.0%
11.50
12.32
6.33
8.5%
11.48
12.50
13
53.37
3C273
0.85
Ar1-0.2
--
-0.94
-0.36
-740
7.05
13.4%
18.17
28.56
5.43
6.9
11.69
12.26
6.3
8.3%
11.25
12.57
15
52.45
3C273
0.65
Ar1-0.4
--
-0.98
-0.36
-759
7.49
10.5%
17.53
23.03
5.44
7.6%
11.29
12.67
6.39
9.0%
11.18
12.58
17
51.44
3C273
0.45
Ar1-0.6
--
-0.86
1.14
-966
7.82
9.3%
17.54
21.00
5.00
10.8%
11.28
14.51
5.95
11.4%
11.31
13.69
19
50.30
3C273
0.25
Ar1-0.8
--
-1.42
-0.18
-1170
8.06
7.6%
17.78
19.17
4.50
16.8%
12.47
18.93
5.15
16.6%
12.37
17.13
21
48.88
3C273
0.05
Ar1-1.0 = Ar2 focus
--
-1.50
-0.23
-1228
8.12
6.7%
17.71
18.79
4.43
21.9%
15.50
24.61
5.04
21.1%
14.66
22.37
23
47.49
3C273
-0.15
Ar1-1.2
--
-1.53
-0.27
-1245
7.99
7.7%
17.53
10.12
4.66
22.0%
19.57
29.36
5.17
24.7%
18.30
26.48
25
45.97
3C273
1.05
Ar1 focus
--
-1.47
-0.15
-1219
7.11
8.4%
17.96
21.77
5.48
6.5%
11.24
11.74
6.46
6.5%
11.02
12.09
NOTE 1: the focus values listed here do already include the -0.2 adjustment for the curved focal surfaces
NOTE 2: the Ar3 absolute flux calibration is incorrect because no DAFs CAL are available yet
NOTE 3: focus performed in scans 4-8, Ar1=1.05; Ar3=1.05; Ar2=out of range
NOTE 3b: focus checked again at the end of the exercise, in scans 26-30, Ar1=1.05; Ar3=1.03; Ar2=out of range; good; the focus kept stable along the whole test.
NOTE 4: windy records = percentage of records rejected because of too large tracking deviations
NOTE 5: the Temperatures of the back structure etc. are recorded at the start of the calib_1scan
Test of focus difference between the three arrays after cryostat warm-up and cool-down cycle (April 25, 2026)
AoD: Ioannis
Outline of test slot T21-25:
- Started with the test on-time (21:00 LT)
- Tuning instrument with cryostat window closed (run92.ini). Bad kids 12/5/11 for Ar1/Ar2/Ar3. No bumps in DAQ traces for all arrays, instrument looks in very good condition.
- Tuning instrument with cryostat window open. Bad kids 47/13/28 for Ar1/Ar2/Ar3. No bumps in DAQ traces for all arrays, instrument looks in very good condition.
- Pointing and several focus sequences on 3C273. Stability at the beginning at +/- 3 Jy/beam at 2mm.
- Going to 3C279 for another focus test. Stability gets worse at +/- 7-10 Jy/beam. Opt focus for Ar2 and beam is 16.98x18.42
- Later stability improved again at +/- 2-3 Jy/beam
- Back to 3C273 for the calib_1scan series test at different focus positions. Results listed below. Consecutive scans showed strangely a pointing disagreement between the arrays with 2-3 arcsec differences in both Az and El.
- Conditions get much poorer at the end with +/- 20 Jy/beam (2mm)
As of 2026/04/25 @22:00 UT.
The focus difference Ar1-Ar2 is roughly +1.20 mm.
The focus difference Ar3-Ar1 is roughly -0.05 mm.
Focus sequences
Scan nr
Target
Ar2
Ar1
Ar3
Polarized?
Notes
20260425s35-39
3C273
0.81
out
out
no
Started at 1.0 mm; Ar2 good fit; Ar1 and Ar3 fit is out
40-44
3C273
out
1.97
1.93
no
Started at 2.0 mm; Ar1 and Ar3 good fit; Ar2 out of range
45-49
3C273
0.91
out
out
no
Started at 1.4 mm to catch all 3 focus positions but just missed Ar1 and Ar3
51-55
3C279
out
out
out
no
started at 1.6 mm to catch all 3 focus positions but all arrays out of range
56-60
3C279
0.79
out
out
no
Started at 1.0 mm; Ar2 perfect fit; Ar1 and Ar3 out of range
61-65
3C279
out
2.03
1.97
no
Started at 2.0 mm; Ar1 and Ar3 good fit; Ar2 out of range
Study of the NIKA2 beams (TP, point-like target) using calib_1scan
General
Ar2
Ar1
Ar3
Scan nr
Tapas El. [deg]
Target
Z Focus [mm]
Notes
windy records
T diff bck struc [C]
T diff quadripod [C]
Z axis corr by T [um]
MB flux [Jy]
Side lobes %
FWHM min [arcsec]
FWHM max [arcsec]
MB flux [Jy]
Side lobes %
FWHM min [arcsec]
FWHM max [arcsec]
MB flux [Jy]
Side lobes %
FWHM min [arcsec]
FWHM max [arcsec]
20260425s67
49.58
3C273
2.03
Ar1 focus
--
-2.38
+0.33
-2091
7.74
11.6%
18.24
23.26
4.26
11.4%
11.53
11.68
4.35
12.3%
11.10
12.68
69
50.49
3C273
1.63
Ar1-0.4
--
-2.39
+0.29
-2091
8.30
9.2%
17.66
20.77
3.79
14.6%
11.96
12.84
3.99
14.3%
11.13
14.28
71
51.26
3C273
1.23
Ar1-0.8
--
-2.28
+0.39
-2018
8.31
8.1%
17.65
19.76
3.13
20.4%
13.68
17.29
3.35
20.9%
12.47
18.40
73
52.08
3C273
0.83
Ar1-1.2 ~ Ar2 focus
--
-2.32
+0.34
-2042
8.47
8.6%
17.77
19.11
2.93
32.3%
17.11
22.32
3.26
29.0%
16.20
22.54
NOTE 1: the focus values listed here do already include the -0.2 adjustment for the curved focal surfaces
NOTE 2: windy records = percentage of records rejected because of too large tracking deviations
NOTE 3: the Temperatures of the back structure etc. are recorded at the start of the calib_1scan
A new test of focus difference between the arrays: May 19, 2026
- Thanks to Brisa and the heterodyne pool week Team for this opportunity.
- Cryostat has been cool since April 24, 2026. During the morning maintenance slot, Dave noticed a clear, relatively wide bump at ~1.4 Hz in the noise traces of array 1, with the window closed.
- Starting the preparation for the focus test at 21:00; anomalous refraction/unstable atmosphere during the preceding hours; tau_225GHz~0.25; pretty clear sky, no wind. DAQ started at 21:15 right after finishing an EMIR scan; window closed, bad KIDs (ar1, 2, 3): 14/1000, 7/574, 10/749. Noise traces:
- DAQ restarted at 21:25; window open, blank sky, bad KIDs (ar1, 2, 3): 17/1000, 7/574, 17/749. Noise traces:
- First pointing on 1226+023 (3C273), El. ~51.5 deg.; p2p var. ~5 Jy/beam (2 mm); superb tracking.
Focus sequences (preliminary)
Scan nr
Target
Ar2
Ar1
Ar3
Polarized?
Notes
20260519s234-238
3C273
0.23
(1.41)
(1.43)
no
Started at 1.0 mm; Ar2 good fit; Ar1 and Ar3 fit from FWHM's only
239-243
3C273
no
1.53
1.54
no
Started at 1.45 mm; Ar1 and Ar3 good fit; Ar2 out of range
244-248
3C273
0.56
out
out
no
Instabilities increasing; started at 0.3 mm; Ar2 good fit; Ar1 and Ar3 very bad
250-254
3C279
(0.54)
1.59
1.52
no
Started at 1.7 mm; Ar2 fit from FWHM's only; Ar1 and Ar3 good fit
255-259
3C279
0.55
out
out
no
Started at 0.6 mm; Ar2 good fit; Ar1 and Ar3 very bad
- Best-fit plots:
