Calibration and performance of the NIKA2 camera at the IRAM 30-m Telescope

Open Access

Table 2.

Field-of-view deformation.

Characteristic	Array 1	Array 3	Array 2
λ [mm]	1.15	1.15	2.0
Design detectors	1140	1140	616
Selected KID ^(a)	866	808	488
Well-placed KID ^(b)	864	808	488
Deviation ^(c) [″]	1.01	0.95	0.75
Distortion ^(d) [″]	1.09	1.01	0.84
Array centre ^(e) [″]	(1.9, −5.1)	(2.3, −6.2)	(9.6, −7.8)
Scaling ^(f) [″ mm⁻¹]	4.9	4.9	4.9
Rotation angle ^(g) [°]	77.3	76.3	78.2
Grid step ^(h) [″, mm]	9.8, 2.00	9.7, 2.00	13.3, 2.75
Grid step ⁽ⁱ⁾ [λ/D]	1.11	1.10	0.87
Modelled grid step ^(j) [λ/D]	1.09	1.09	0.93

Notes. Example of mapping of the observed KID positions in the sky to their mechanically designed positions. The initial table of selected KIDs is given by the focal plane geometry procedure, as described in Sect. 5.1, and applied to a beammap scan acquired during the N2R12 campaign. More than 90% of the detectors are within less than 5″ of their expected position.

^(a)

Initial number of KIDs selected in a FOV geometry using a beammap scan of the N2R12 campaign.

^(b)

Number of KIDs for which the best-fit sky position is less than 4″ away from the expected position.

^(c)

Median angular offset in arcseconds between the expected and measured sky position of the KIDs.

^(d)

Average best-fit cross term of the polynomial model across the FOV given in arcseconds.

^(e)

Array centre in Nasmyth coordinates.

^(f)

Averaged scaling between measured KID position grid and the designed one.

^(g)

Rotation from the design to Nasmyth coordinates given in degrees.

^(h)

Centre-to-centre distance between neighbour detectors.

⁽ⁱ⁾

Centre-to-centre distance between neighbour detectors using the reference frequencies (260 GHz and 150 GHz) and a 27-m entrance pupil diameter (see Sect. 2.2).

^(j)

Centre-to-centre distance between neighbour detectors modelled using ZEMAX simulation.

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