Why is it interesting?
It is possible to infer the properties of a surface from the way it scatters light. Surfaces that are quite rough tend to show a surge in the reflected radiance as the angles of emission and incidence reach zero. The sizes of the particles that make up the surface also play a role. The scattering is complicated but in recent years several theoretical developments have been made (notably by Bruce Hapke and Michael Mischenko), which we can now test by experiments. The results can be used to test model of the scattering properties of surfaces on, for example, Mars, Mercury and the Moon.
We are interested in the scattering properties of surfaces for several reasons. Firstly, we have been using the experiment to study the reflectance behaviour of simulants of the Mercury surface. This will be important for calculating signal to noise ratios for the BepiColombo Laser Altimeter (BELA). Secondly, the reflectance properties of Martian surface materials have been of interest to us in the past, particularly for Mars Pathfinder and for the MER missions. We are also interested in measuring photometric properties of icy samples containing impurities, analogues to cometary surfaces or icy satellites, in support of the ROSETTA (VIRTIS, OSIRIS) and JUICE missions (GALA). Finally, the surface of Titan may have some rather bizarre surface materials. PHIRE-1 and -2 can be used to study whether the scattering properties of these materials are unusual.