Electrostatic Potential Shielding in Representative Cislunar Regions

Abstract

Touchless potential sensing of neighboring spacecraft using photoemissions and secondary electron emissions has been investigated for geosynchronous (GEO) applications. As more missions are being sent to cislunar space, this technology may be extended there as well. However, the complexity of the cislunar environment presents novel challenges for touchless potential sensing technology. A chief issue is shorter Debye lengths than in GEO regions, which can be as low as 10 m in the cislunar regions. Therefore, a model for the electric and potential fields surrounding a charged spacecraft in short Debye regions around the moon is investigated. The vacuum (Laplace) and Debye–Hückel models are presented and effective Debye lengths are used to expand the models and better represent the environment. The effective Debye length has previously been investigated in low Earth orbit (LEO), quiet GEO, and asteroid environments but has not been found in the cislunar plasma environment, and a larger effective Debye length may allow touchless potential sensing using electron emissions to be possible at farther, safer distances than expected. Once the effective Debye lengths and associated models are established, the relationship between effective Debye lengths and touchless potential sensing capabilities is explored through computations in NASCAP-2k, a spacecraft–plasma interaction software. The developed methods are then used to determine whether passive and active touchless potential sensing is feasible in cislunar regions with nonnegligible electrostatic potential shielding.