A photovoltaic (PV) array simulator, consisting of a computer controlled d.c. power supply producing up to 100 W and associated control software, was designed and developed to generate real-time current-voltage (I-V) output characteristic curves of photovoltaic cells under simulated conditions. The system is also capable of modelling radiation damage due to high energy particles. The system comprises a pre-regulator, a switch-mode regulator, a computer interface, and modelling and control software. The control software uses feedback of the output voltage and current to iteratively converge to the actual operating point for the connected load. Simulation results match the expected theoretical calculations well. The main advantage of the simulator is its ability to simulate different types and sizes of arrays under varying illumination and temperature using actual loads. The system can be used to study the short-term and long-term performances of PV modules and to predict end-of-life efficiency. The simulator is a far more cost effective and reliable replacement for actual field testing.