Photometric modelling for laboratory measurements of dark volcanic sand

- Goniometric measurements of the BRF of black volcanic sand.
- Measurements with different treatments for the roughness of the surface.
- A good quality set of measurements is obtained.
- Testing the applicability of a semi-numerical scattering model.
- Good fits to the measured data are obtained.

We have performed laboratory measurements of the bidirectional reflectance factor (BRF) of a sample of dark volcanic sand. The measurements were carried out with three different treatments of the sample to produce different porosity and roughness characteristics. We model the measured BRF with a semi-numerical scattering model for particulate media, meant especially for dark planetary regoliths. We compare the BRF in two different spectral bands, 500-600 nm and 800-900 nm. The particulate medium (PM) scattering model is found to fit the measured data well, with a phase function representing the differences between the spectral bands. The interpretation of the physical parameters of the PM model is qualitatively sound, but remains somewhat uncertain due in part to the difficulty of characterizing the measured sample.