In this paper we apply the techniques of data assimilation to the problem of radial diusion,of electrons in the radiation belts. Unlike previous studies, the objective of this work is not to reproduce observations but rather to determine the diusion,parameters regulating the physical behavior of the radiation belts. We developed a code containing a radial diusion solver and a Kalman filter and show how the assimilation of data could potentially pin-down the most likely diusion,parameters. We supplied our assimilation model with artificial data in an identical twin experiment in order to illustrate the strengths and capabilities of data assimilation techniques. We find that there is a degeneracy in the parameterized diusion,function and that these parameters are anti-correlated. We discuss how this