CCFs for ¹³CO and H₂¹⁸O. The CCFs are calculated for each order-detector pair and summed over all orders and detectors. The CCFs are converted to S/N by dividing them by the standard deviation of the CCFs away from the peak (|υ_rad| > 100 km s⁻¹). The S/N of the peaks of the CCFs is shown in the legend. The residuals between the observed and modelled CCFs – the auto-correlation function (ACF) – are shown in the bottom panel.