Total system response for the NISP grisms and emission line signal-to-noise ratios (S/N). Top panel: total system response for the NISP blue grism (shaded area, exceeding 50% of its peak transmission between 0.93–1.37 µm; these data are updated with respect to those presented in ESc22). The regularly spaced, grey spectrum shows the arbitrarily scaled Fabry-Perot emission lines used for the pre-flight calibration of the dispersion law. As an example for the in-flight calibration, the purple spectrum shows the estimated NISP S/N of He2-436, extrapolated from our X-shooter observations. The horizontal dashed line displays a 3.5σ threshold to identify usable PN lines. Bottom panel: same as for the other panel, but for the NISP red grism (1.21–1.89 µm).