The development of high power, high voltage solar arrays for spacecraft has increased the risk of damage by electrostatic discharge mechanisms, and examples already exist of recently launched 10 kW+ spacecraft which have experienced solar array damage in their first year of operation. While recent analysis coupled with space and ground-based experiments has produced further insight into the problem, unresolved issues continue to exist.In the present experiments, simulation of the GEO space environment has been improved compared to past studies. An electron gun charges the solar cell circuit and its substrate using variable current and energy settings, at 1×10-7 Torr background pressure. A solar simulator lamp provides photons over the 200 nm to near infrared spectral range. The temperature of the substrate is controlled, and a floating power supply simulates the remainder of the solar cell string.As expected, the substrate and insulator surfaces can be charged to kV levels by the electron beam. The charge levels have been investigated as a function of electron current and energy, and light impingement. Preliminary results are presented regarding the occurrence of electrostatic discharge phenomena, considering the influence of solar cell circuit, temperature, light impingement, electron energy and flux levels.