Phase ratio in single-scattering dust particles: Implication to future DESTINY+ study of asteroid (3200) Phaethon

The phase ratio is defined as a ratio of reflectivity of object at two different phase angles α. This light-scattering characteristic has revealed high sensitivity to physical parameters of a planetary regolith. We investigate the phase ratio of single-scattering irregularly shaped particles with different morphology by means of the discrete dipole approximation. The phase ratio defined at α = 0° and 30° appears to be highly sensitive to the imaginary part of refractive index and less sensitive to the size distribution of target particles; whereas, it is not sensitive to their real part of refractive index and irregular morphology when it attains a high level of disorder. Further, the phase ratio defined at α = 30° and 60° is almost fully insensitive to microphysics of target particles. This feature might help to enhance the scientific return from the future DESTINY+ mission to asteroid (3200) Phaethon.