Space experiments with particle accelerators (SEPAC) on Atlas-1 space transportation system (STS-45) included a plasma contactor to neutralize charge buildup on the orbiter due to electron accelerator operations. The SEPAC plasma contactor operated the same as it had during testing in the laboratory. During SEPAC electron accelerator operations, the contactor emitted currents that helped balance the electron beam current. The Langmuir probe measured the charge exchange ions and the thermal electrons emitted by the contactor. The electric field wave data showed an order of magnitude increase in the 4-8 MHz band. There were no reports of contactor operations interfering with either orbiter systems or other Atlas-1 experiments.