Data assimilation methods are becoming increasingly popular to describe the observationally sparse environment in Earth’s magnetosphere. As energetic electrons pose a number of hazards to manned and unmanned spacecraft, the outer radiation belts are an especially high profile candidate for data assimilation techniques. Energetic electron diffusion can be simplified with a Fokker-Plank equation, which also allows for the ability to include loss or source terms. We use a one-dimensional radial diffusion model, a five satellite Phase Space Density (PSD) data set (three LANL-GEO, one GPS, and POLAR – all for constant first and second adiabatic invariants), and a conventional Kalman filter (CKF) to describe the energetic electron PSD for the full radial range of the outer radiation belt. Additionally, we augment the state vector to include the magnitude of a Gaussian-shaped local acceleration term. The result of the analysis is an estimate of electron PSD, as well as a time-dependent heating rate for specified location and width. To further constrain the source rate parameters, such as the location and width of the acceleration region, additional analysis is performed using the observational residual vector (or innovation vector) by quantifying the root mean square (RMS) of the vector in a location-width parameter space.