Abstract: Exposure of Mylar and Teflon films to combine dhigh-/medium-/low-energy electrons has been performed whose results differ from that of exposure to medium-energy electron environment alone, combined high-/medium-energy electron environment, and combined medium-/low-energy electron environment. The experimental results have shown that dielectric discharge can be initiated by highenergy electron exposure. The results of exposure of Teflon films to combined high-/medium-/low-energy electron environment agree with that of exposure to 1—100keV dN/dE∝E~(-2) spectral energy electron environment and that of NASCAP computer simulation. It is concluded that combined high-/mediumow-energy electron exposure can perfectly simulate charging and subsequent discharging effects of dielectrics aboard geosynchronous satellites. Necessity and sufficiency of using electrons with the three different energies have been demonstrated. It is inferred that the surface potential of dielectrics on spacecraft surface will be raised and discharges will be initiated if high-and/or mediumenergy electron fluxes increase to an adequate value in geosynchronous orbit during geomagnetic storm or substorm.