The Hapke parameters are a set of parameters for an empirical model that is commonly used to describe the directional reflectance properties of the airless regolith surfaces of bodies in the Solar System. The model has been developed by astronomer Bruce Hapke at the University of Pittsburgh.
The main parameters are: [1]
The Hapke parameters can be used to derive other albedo and scattering properties, such as the geometric albedo, the phase integral, and the Bond albedo.
The Hapke model has been criticized for having a large number of unconstrained parameters that can make the parameters difficult to constrain. [3] [4] In particular, the model has been shown to often require unphysical parameters (e.g., the asymmetry factor) when modeling the albedo of ices. [5] [6] [7] [8]