In practice, measurements at small nonzero phase angles are used to derive the parameters which characterize the directional reflectance properties for the body ( Hapke parameters ).
2.
In detailed studies, the directional reflectance properties of astronomical bodies are often expressed in terms of the five Hapke parameters which semi-empirically describe the variation of albedo with phase angle, including a characterization of the opposition effect of regolith surfaces.
मोबाइल