Synthetic ice spectra of a ‘simple’ ice composition, containing only the major ice species and S-bearing molecules in the NIRSpec wavelengths. The spectral information used for each species (band shapes, positions and band strengths) are listed in Table A.1. The column densities of H₂O, CO, CO₂, CH₃OH used to plot these spectra are, respectively, 3.0 × 10¹⁸, 3.0 × 10¹⁷, 3.0 × 10¹⁷, and 5.0 × 10¹⁷ molecules cm⁻², while we assume 1.0 × 10¹⁶ molecules cm⁻² for all four S-bearing species (H₂S, OCS, SO₂, and CS₂). The zoom panel emphasises the low band strength of the band corresponding to H₂S, as well as its overlapping with the methanol combination mode. The red line is the signal that would be obtained with the most basic settings in SynthIceSpec (pure species with no mixing). In this wavelength range, of the S-bearing species, only OCS and H₂S present absorption features.