NISP encircled energy as function of radius. Left: EE of the NI-OA at λ = 960 nm based on SHS measurements. Shown in red is the EE for the field centre, and in blue for the field edge. The ideal aberration-free or diffraction-limited case is given by the dashed black line. Right: enlarged section of the full range of radii on the left. The radii for the 50% and 80% EE values are expressed as a percentage of the diffraction-limited case. The x-axis is represented in physical units and in pixels.