An empirical model of radiation belt relativistic electrons (m = 560–875 MeV G^–1 and I = 0.088–0.14 R_E G^0.5) with average energy ~ 1.3 MeV is developed. The model inputs solar wind parameters (velocity, density, interplanetary magnetic field (IMF) |B|, Bz, and By), magnetospheric state parameters (SYM-H, AL), and L*. The model outputs radiation belt electron phase space density (PSD). The model is operational from L* = 3 to 6.5. The model is constructed with neural network assisted by information theory. Information theory is used to select the most effective and relevant solar wind and magnetospheric input parameters plus their lag times based on their information transfer to the PSD. Based on the test set, the model prediction efficiency (PE) increases with increasing L*, ranging from –0.043 at L* = 3 to 0.76 at L* = 6.5. The model PE is near 0 at L* = 3–4 because at this L* range, the solar wind and magnetospheric parameters transfer little information to the PSD. This baseline model complements well a class of empirical models that input data from Low Earth Orbit (LEO). Using solar wind observations at L1 and magnetospheric index (AL and SYM-H) models solely driven by solar wind, the radiation belt model can be used to forecast PSD 30–60 min ahead.