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Table 2

Summary of the parameters employed in the NIRSpec parametric model of the spectrograph.

Number of parameters
Element Type Description Total Free

Optical module Paraxial transform Input plane center 2
COL, CAM Output plane center 2
Rotation angle 1
Scaling factors 2
Geometrical distortion Forward 2D polynomials 21 × 2 21 × 2
Backward 2D polynomials 21 × 2 21 × 2

MSA Quadrant positions Position of shutter (1, 1) 2 × 4 2 × 4
Rotation angle 4 4
Shutters Pitch size 2 × 4 2 × 4
Aperture size 2 × 4
Fixed slits Absolute position 2 × 5 2 × 5
Aperture size 2 × 5

GWA Dispersers Alignment angles 3 × 8 3 × 6
Grating dispersion Front surface tilt 6
Groove density 6
PRISM dispersion Front surface tilt 1
Internal prism angle 1
Sellmeier refractive index 8
Temperature and
pressure dependence 6

FPA Detector positions Position of pixel (1, 1) 2 × 2 2
Rotation angle 2 1
Pixel positions Pitch size 2 × 2

IFU Slicer position Absolute position 2
Rotation angle 1
Slices Relative position 2 × 30
Aperture size 2 × 30
IFU-FORE Optical module Paraxial + 2D polynomials 7 + 21 × 2
IFU-POST 30 Opt. modules Paraxial + 2D polynomials (7 + 21 × 2) × 30 3 × 30

Notes. All of the parameters needed to transform a point from one focal or pupil plane are listed here. The two last columns give the total number of available and free parameters in the optimization process described in Sect. 5.

(†)

The prism was not included in this work and the mirror alignment was set to fixed angles.

(‡)

Only for SCA492.

(♣)

Only the center position and rotation of the output plane of each IFU-POST paraxial part were optimized.

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