Relationship between phase function parameters b and c. (a) shows the parameters derived from the two-term Legendre polynomial function, and (b) shows the parameters derived from the HG function. The b and c values of olivine, orthopyroxene, plagioclase, and ilmenite were obtained by Yang et al. (2019). The empirical b and c values were obtained from Lucey (1998). The CE4 in situ b and c values were obtained from Yang et al. (2020). The L-shaped region and the nature of its different parts were obtained from McGuire & Hapke (1995). “CE4 SWIR” means the short-wavelength infrared detector of the CE4 mission, and “CE4 CMOS” means the complementary metal-oxide semiconductor imager of CE4.