Numerical Determination of the Internal Scattering Coefficient from Reflectance Spectra of Meteorites and Minerals

Abstract

In this work, the internal scattering coefficient s was obtained as a function of wavelength from reflectance measurements of a suite of eight particulate samples in the VIS/NIR from RELAB database. First, the imaginary part of the index of refraction was retrieved by inverting the reflectance spectra using the Hapke's model, incorporating the porosity correction. No a priori assumptions were made  for any parameter values during this inverse process. The average value of the internal scattering coefficient obtained from the spectra inversion at the center of the first absoption band was 0.0692 𝜇m^-1. This is of the same order of magnitude as the value reported in the literature for a synthetic silicate glass sample. Additionally, values of s were derived for individual particle size ranges by fitting each spectrum using the average imaginary refractive index. The resulting values of s fell in the range 0 to 0.102 𝜇m^-1,  corresponding to particle diameters from 37.50 to 310.12 𝜇m. For this type of analysis, a positive correlation between s and particle diameter D is typically expected. However, with the methodology employed here, most samples showed either a negative or a weak correlation; only one sample exhibited a positive correlation. Consequently, it is not possible to definitively conclude whether a correlation exists between s and D, based on these results, indicating that further analysis is required.