Example of local continuum spline fitting and modelling of the CO₂ (top panel), H₂O (middle panel), and (bottom panel) ice absorption feature’s optical depth. The dashed line shows the model for the thermal continuum fit to red points on either side of the ice feature, while the solid black line indicates the cubic spline fit. The data is shown in green for source A. The majority of unlabelled emission features in the lower panel are H₂O emission.