Illustration of data combination and background subtraction. The grey spectra show the 1728 acquisitions of cube T1-00400765976 acquired on 13 September 2015 from 11h:46m:19.3s to 15h:24m:49.8s UT. The orange spectrum is the averaged spectrum, and the blue spectrum is the average spectrum obtained after subtraction of the continuum background, following the method explained in the text. This cube, which shows extreme variations in dust continuum because it was acquired during an outburst (Bockelée-Morvan et al. 2017), was not considered for this paper.