Extracted phase curves and color ratio curves. (a) Comparisons of the CE-4 (orange, this work) and CE-3 (blue, Jin et al. 2015) phase curves in the R band (640 nm). For CE-4 data, the gray color dots represent pixel densities (with a bin width of 0.375 on the phase-angle axis and 0.000375 on the reflectance axis) of the original reflectance values and the red curve with error bars is the averaged value within a 1° phase angle; and (b) reflectance in the R band (640 nm) normalized at a 2° phase angle. We note that the minimum phase angle of the CE-4 phase curve is 1°, while that of CE-3 is 2°. (c) Reduced reflectance values obtained from Eq. (3); (d) reduced reflectance normalized at a 2° phase angle;(e) extracted phase curves in three colors for CE-4: red (R, 640 nm), green (G, the average of two 540 nm channels G1and G2), and blue (B, 470 nm); and (f) color ratios of red over blue and green over blue for CE-4.