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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
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.
Study of the NIKA2 beams (TP, point-like target) using calib_1scan
General
Ar2
Ar1
Ar3
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
3C279
1.29
Ar1-0.3 mm
173
3C279
1.19
Ar1-0.4 mm
175
3C279
1.09
Ar1-0.5 mm
177
3C279
0.99
Ar1-0.6 mm
179
3C279
0.89
Ar1-0.7 mm
181
3C279
0.79
Ar1-0.8 mm
183
3C279
0.69
Ar1-0.9 mm
185
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