  The Lunar Orbital Platform-Gateway (LOP-Gateway, or simply Gateway) is a
crewed platform that will be assembled and operated in the vicinity of the Moon
by NASA and international partner organizations, including ESA, starting from
the mid-2020s. It will offer new opportunities for fundamental and applied
scientific research. The Moon is a unique location to study the deep space
plasma environment. Moreover, the lunar surface and the surface-bounded
exosphere are interacting with this environment, constituting a complex
multi-scale interacting system. This paper examines the opportunities provided
by externally mounted payloads on the Gateway in the field of space plasma
physics, heliophysics and space weather, but also examines the impact of the
space environment on an inhabited platform in the vicinity of the Moon. It then
presents the conceptual design of a model payload, required to perform these
space plasma measurements and observations. It results that the Gateway is very
well-suited for space plasma physics research. It allows a series of scientific
objectives with a multidisciplinary dimension to be addressed.
