Variation of the depth of the 2.0 μm absorption band (in %) calculated as a function of time (MJD − 55 660 days). The 2007 data have been shifted by an integer number of rotational period so that they can be overplotted on the 2011 data (see Table 1). The red circles and blue triangles correspond to the 2007 and 2011 data, respectively. All spectra were normalized at 2.225 μm for this study. The error bars are 1σ uncertainty for both data. Haumea’s light curve (solid line) is also represented for clarity. Values corresponding to the absorption band depth are in the [40–60%] range with a smallest water-ice absorption at 10° close to the lowest minimum of the light curve with no significant difference between DRS and no-DRS.