Observations of Differential Charging Effects on Ats 6

Differential charging effects observed in the electron data of the University of California, San Diego, auroral particles experiment on Applied Technology Satellite 6 are described and analyzed. An electrostatic barrier around the environmental measurements experiment (EME) package on ATS 6 is shown to be the natural result of dielectrics around the spacecraft which are more negatively charged than the main-frame of the spacecraft. In particular, the large dish antenna on ATS 6 causes the formation of a barrier which traps particles emitted from the EME package surface and returns them to the spacecraft. The insulating surface of the rotating University of Minnesota detector on the otherwise conducting EME package is shown to be the source of accelerated fluxes of electrons during charging events.