Material_properties Properties related to the material. surface_roughness Information about the surface roughness of the material. Required: Yes surface_height_rms Root mean square of surface height deviations. Required: Yes surface_correlation_length Correlation length of the surface height deviations. Required: Yes elasticity_data Information about the elasticity of the material. Required: Yes youngs_modulus Young’s modulus of the material in Pa. Required: Yes poissons_ratio Poisson’s ratio of the material. Required: Yes source Source of the elasticity data. Required: Yes density_data Information about the density of the material. Required: Yes density Density of the material in kg/m^3. Required: Yes source Source of the density data. Required: Yes electromagnetic_properties_uri Relative path to a property lookup table file with electromagnetic material properties. Pattern: .*_emp\\.xompt$ Required: Yes retroreflectivity_data Information about the retro-reflective properties of the material in the visible light spectrum. Required: No coefficient_of_retroreflection Coefficient of retro-reflection in cd lx^-1 m^-2. Required: Yes source Source of the retro-reflectivity data. Required: Yes