ABSTRACT
Spacecraft charging to high negative voltage may interfere with the scientific measurements onboard and harm the electronic instruments. Any low-level voltage due to charging can be tolerated usually, because it does not cause significant interference in the electronics, nor does it cause severe harm on the instruments. Positive ions are also emitted from sharp points by positive electric fields about ten times stronger. The thermionic emission method can also be used for mitigation of spacecraft charging by means of electron emission. The thermionic emission method is an active method. It requires a command from the ground to turn on the hot filament. Low-energy positive ion emission from a highly negatively charged spacecraft can produce an ion fountain. The low-energy ion beam emission method is effective in mitigating differential charging. Low-energy missions of electrons and positive ions are more efficient than low-energy ion emission alone.
