Plasma probes for the lunar surface

Dust particles on the lunar surface, or on any other airless planetary surface, can be directly exposed to solar wind plasma and ultraviolet radiation, resulting in electrostatic charging and possible subsequent mobilization and transport. Although there are several independent observations indicating dust levitation and transport on the Moon, these processes are still poorly understood, and the development of specialized plasma and dust diagnostic tools will be necessary for future missions. Here we discuss a measurement technique that could characterize the near surface lunar plasma environment. We report on laboratory experiments using an asymmetric double probe with vastly different collection areas to characterize the sheath above a photoemissive surface in a vacuum chamber. The approach could form the basis of a future in situ experiment that probes the photoelectron layer on the lunar surface.