The highly energetic electron environment in the inner magnetosphere (geosynchronous Earth orbit (GEO) inward) has received a lot of research attention in resent years, as the dynamics of relativistic electron acceleration and transport are not yet fully understood. These electrons can cause deep dielectric charging in any space hardware in the medium Earth orbit (MEO) to GEO region. We use a new and novel approach to obtain a global representation of the inner magnetospheric energetic electron environment, which can reproduce the absolute environment (flux) for any spacecraft orbit in that region to within a factor of 2 for the energy range of 100 KeV to 5 MeV electrons for any level of magnetospheric activity. We combine the extensive set of inner magnetospheric energetic electron observations available at Los Alamos with the physics-based Salammbô transport code using the data assimilation technique of “direct-insertion.” This, in effect, inputs in situ data into the code and allows the diffusion mechanisms in the code to interpolate the data into regions and times of no data availability. Here we present details of the methods used both in the data assimilation process and in the necessary intercalibration of the input data used. We present sample runs of the model/data code and compare the results to test spacecraft data not used in the data assimilation process.