Absolute calibration of the Mariner 10 filters with MDIS and MASCS data. Dashed gray line is MASCS observation VIRSVC_OB2_12304_234502 of our test area in Budh Planitia (18.8°N, 211.0°S), acquired at 79° phase. Blue line is the same spectrum after applying a scaling coefficient (1.86058) to match the median MDIS 560 nm reflectance of the same location. Orange squares are MDIS band centers included in the eight-color mosaic (normalized to i = 30°, e = 0°, g = 30°, retrieved from the Astrology Science Center; S. E. Hawkins et al. 2007, 2009; B. W. Denevi et al. 2018). Green circles are the Mariner 10 band centers after applying coefficients (UV = 0.045461, BL = 0.037407, OR = 0.080899) to fit them to the MDIS-calibrated MASCS spectrum.