APEX (Advanced Photovoltaic & Electronic Experiment) successfully tested a wide array of advanced photovoltaic and electronic components in a harsh radiation environment, provided significant data to support improved designs for future space systems. During operation, APEX’s highly elliptical orbit allowed the investigation of space plasma effects on high-voltage operation (current leakage at positive voltages and arcing at negative voltages) in the perigee region, plus the investigation of space radiation effects (decreased array power output from passage through the inner radiation belt) in the apogee region.