Mineral abundances inferred from in-situ reflectance measurements of Chang'E-4 landing site in South Pole-Aitken basin

Figure 2. (a) Original in-situVNIS reflectance spectra expressed in reflectance factor measured by CE-4 during the first two lunar days; (b) the six spectra normalized at 750 nm. Comparisons of continuum-removed measurement spectra of six different sites with the corresponding best-matched LUT spectra obtained using fourdifferent fitting metrics are shown in (c)~ (h). (c) for N15, (d) for N16, (e) for N17-1, (f) for N17-2, (g) for N18-1, and (h) for N18-2, respectively.

Figure 3.Average M³spectra of selected typical units. The locations of selected areas in (a) and (b) are marked in Figure 1band Figure 1a, respectively.

Figure 4. The ternary diagram of PLG-PYX-OLV abundances of (a) the CE4 landing site and selected ROIs within the Von Kármán (VK) crater; (b) the CE4 landing site and selected ROIs outside the VK crater extracted from the CE-4, M³and Kaguya Lunar Multiband Imager (MI) data; (c) the plot of CPX abundance vs OPX abundance of the CE4 landing site and selected ROIs extracted from the CE-4, M³and MI data. Note the abundances are relative.The different results of M³and Kaguya/CE-4 are probably caused by their different spatial resolutions.

Figure 6. Principal component analysis results of CE-4 landing site. (b) PC2 vs PC1 and (c) PC4 vs PC3 are distributions of the typical PC values of selected ROIs calculated from the M³spectra in the PC space.

Figure S1.The original CMOS spectrum, original SWIR spectrum and the scaled CMOS  spectrum of N18-1 measurement site. Reflectance was obtained by using Eq.(S1). After scaling the CMOS spectrum to the SWIR spectrum, the two spectra agree with each other well in the overlapping region and the scaling did not introduce any distortions to the 1 mm absorption feature.

Figure S2. Reflectance in REFF at six measurement sites using solar irradiance calibration (red dots) and the onboard calibration target method (blue squares).

Figure S3. Continuum-removed measurement spectraat six sites using the solar irradiance calibration (red dots) and onboard calibration target method (blue squares).

Figure S4.Relative differences of REFF for the six measurements shown in Figure S2. The relative difference was obtained by (eq.(S3) – eq.(S1))/eq.(S3)).

Figure S7.Retrieved mineral abundances by using reflectance spectra obtained by using the solar irradiance (Eq. S1)) and onboard calibration target (Eq. (S3)) calibration methods. The absolute differences between the two results are also shown. It can be seen that measurements with shadows in either the lunar surface (N17-1) or calibration target (N17-2) have incurred larger differences.

Figure S8. Comparisons of continuum-removed measurement spectra of selected areas (Figure 1a) of M³data and the corresponding best-matched LUT spectra obtained using fourdifferent fitting metrics (Equations (S4)-(S7))for (a) CE-4 landing site, (b) F1, (c) F2, (d)A1, (e) A2, (f) VKM, (g) VK, (h) H1 and (i) H2, respectively.

Figure S9. Comparisons of continuum-removed measurement spectra of selected areas (Figure 1b) of M³data and the corresponding best-matched LUT spectra obtained using fourdifferent fitting metrics (Equations (S4)-(S7))for (a) CP, (b) C1, (c) C2, (d)C3, (e) C4, (f) C5, (g) C6, (h) C7 and (i) C8, respectively.

Figure S10. Cumulative variances of the first ten principal components.