Noise and S/N distributions obtained with V_mag = 4 and t_exp = 15 min. Top panel: Variance (σ²) of the 1D simulated flux obtained by summing the different noise contributions in quadrature according to Eq. 7. Second panel: Standard deviation (σ) of the 1D simulated flux. Third panel: Noise spectrum obtained by setting its standard deviation as computed in the previous panel. Fourth panel: Synthetic S/N spectrum over the complete spectral range of CubeSPEC, obtained by dividing the 1D signal by its standard deviation. The horizontal orange line shows the median S/N.