In the second year, testing begins in earnest to identify candidate plasma sail materials. At MSFC, we process 3 or more dust samples per week using our automated system. Our goal is produce an empirical (and/or theoretical) model of the light scattering properties of single dust grains by collecting data on the effect of diameter, surface composition, non-sphericity, charge buildup, and magnetization on the radiative scattering.
In addition to the light scattering properties, we also study the photoemissive properties of the dust, and test the theories of equilibrium charge density of the dust grains. Since the force balance enables us to calculate the charge on the grain, we are able to measure the equilibrium charge state of the grain as a function of light intensity and frequency. For some materials (styrene, or surface coated dust) and dependant on the intensity of the tuneable lasers, we may also be able to test the degradation of the materials which would be equivalent to long exposure to sunlight.