Figure 5: a) Reflectance (I/F) as a function of phase angle (g) for the BZs. b) BZ reflectance, normalized to background values. c) Reduced reflectance (IoF/LS), showing compositional differences between landing sites. d) Apollo 12 reflectance versus incidence angle (i), showing the effects of viewing geometry. e) Apollo 12 reflectance versus g. f) Apollo 12 reduced reflectance as a function of g, which masks the effects of viewing geometry and shows increased separation between BZ and background I/F values at higher phase. Figure 2: Apollo 11 landing site, with the LR-BZ and HR-BZ outlined. NAC image M R. Mission Avg. I/F for HR- BZ Avg. I/F for LR-BZ Avg. background I/F Avg. normalized I/F b Elliptical Area (m 2 ) Lander mass (kg) Avg. Thrust c (kN) Ap Ap12 a Ap Ap Ap Ap Apollo avg0.047− L − L − L − L − L − Luna avg − S − − S − − S − − S − − Surv. avg − a Apollo 12 measurements include Surveyor Crater b Normalized I/F = IoF_bz/IoF_background (for HR-BZs) c Calculated from average Apollo, Luna, and Surveyor thrust values a Apollo 12 measurements include Surveyor Crater b Normalized I/F = IoF_bz/IoF_background (for HR-BZs) c Calculated from average Apollo, Luna, and Surveyor thrust values Table 1: Average blast zone measurements and reflectance values for each landing site. Average I/F values are for phase angles of ~30°. Figure 1: NAC images of the Apollo, Surveyor, and Luna landing sites, cropped to the region around the landers. Dashed lines outline the outer extent of each blast zone (HR-BZ). Insets are zoomed in on the lander. a) Apollo 14, image M L. b) Luna 23, image M R. c) Surveyor 1, image M L. (a) Apollo (b) Luna (c) Surveyor Photometric Functions Hapke’s Bidirectional Reflectance Equation (from [6]) Double Henyey-Greenstein Function: Lommel-Seeliger Function (LS): Hapke’s Bidirectional Reflectance Equation (from [6]) Double Henyey-Greenstein Function: Lommel-Seeliger Function (LS): Parameters w = single scattering albedo p(g) = single particle phase function B co = amplitude of Coherent Backscatter Opposition Effect (CBOE) B c = angular shape function of CBOE h c = CBOE angular width parameter S = shadowing parameter b = angular width of forward or backscattering lobe c = magnitude of forward or backscattering lobe i = incidence angle e = emission angle g = phase angle *Bold variables are key parameters Parameters w = single scattering albedo p(g) = single particle phase function B co = amplitude of Coherent Backscatter Opposition Effect (CBOE) B c = angular shape function of CBOE h c = CBOE angular width parameter S = shadowing parameter b = angular width of forward or backscattering lobe c = magnitude of forward or backscattering lobe i = incidence angle e = emission angle g = phase angle *Bold variables are key parameters Figure 6: Preliminary photometric model fitted to BZ reflectance for Apollo 12 (top) and Apollo 16 (bottom). Acknowledgments We thank NASA for support of the LRO mission and the LROC Operations Team for making available the data used in this research. Acknowledgments We thank NASA for support of the LRO mission and the LROC Operations Team for making available the data used in this research. (b) (a) backward (d) wB co hchc bcS Ap Ap Table 2: Parameter values used for modeling in Fig. 6 feldspathic basaltic forward (e) (f) ID: P43B-1931