SSA and continuum-removed SSA. After reflectance calibration, thermal correction, and photometric correction, we used the Hapke model to solve the SSA, and then a Savitzky–Golay filter was applied to the SSA to smooth the spectra. At last, we use the Convex Hull algorithm to detect and remove the continuum; in this way, the relative reflectance can be derived. The x-axis is the wavelength in nm, and the y-axis is the reflectance SSA/continuum-removed SSA (stack for clarity).