Abstract
The lunar ionosphere is a ~100 km thick layer of
electrically charged plasma surrounding the moon. Despite knowledge of
its existence for decades, the structure and dynamics of the lunar
plasma remain a mystery due to lack of consistent observational
capacity. An enhanced observational picture of the lunar ionosphere and
improved understanding of its formation/loss mechanisms is critical for
understanding the lunar environment as a whole and assessing potential
safety and economic hazards associated with lunar exploration and
habitation. To address the high priority need for observations of the
electrically charged constituents near the lunar surface, we introduce a
concept study for the Radio Instrument Package for Lunar Ionospheric
Observation (RIPLIO). RIPLIO would consist of a multi-CubeSat
constellation (at least two satellites) in lunar orbit for the purpose
of conducting “crosslink” radio occultation measurements of the lunar
ionosphere, with at least one satellite carrying a very high frequency
(VHF) transmitter broadcasting at multiple frequencies, and at least one
satellite flying a broadband receiver to monitor transmitting
satellites. Radio occultations intermittently occur when
satellite-to-satellite signals cross through the lunar ionosphere, and
the resulting phase perturbations of VHF signals may be analyzed to
infer the ionosphere electron content and high- resolution vertical
electron density profiles. As demonstrated in this study, RIPLIO would
provide a novel means for lunar observation, with the potential to
provide long-term, high-resolution observations of the lunar ionosphere
with unprecedented pan-lunar detail.