Results from the S₁(λ) model fit on the spectrum of CALSPEC star HD111980, extracted from a simulated spectrogram. Left: spectrum data (red) compared with the best-fitting model (blue) and the model uncertainties (light blue band) due to the CTIO telescope transmission uncertainties, the true injected spectrum in the simulation (green), and the residuals (bottom). Middle: zoom around the dioxygen line at 762 nm and zoom on the H₂O absorption band around 950 nm. Right: correlation matrix of the fitted parameters.