Touchless Potential Sensing of Differentially Charged Spacecraft Using Secondary Electrons

Abstract

The secondary electron method has been recently proposed to touchlessly sense the electrostatic potential of non-cooperative objects in geosynchronous equatorial orbits and deep space. This process relies on the detection of secondaries generated at the target surface that is actively irradiated by an electron beam. Although the concept has already been demonstrated with basic geometries, the electric field around complex bodies leads to a highly inhomogeneous distribution of secondary electrons that determines the observability of the system. This paper employs vacuum chamber experiments and particle tracing simulations to investigate the secondary electron flux generated over a spacecraft-like electrode assembly. The differential charging scenario, in which the assembly is charged to multiple potentials, is also studied. A computationally efficient three-dimensional particle tracing framework that couples the electron beam propagation and secondary electron generation processes is introduced and validated, showing its utility as a diagnostic tool. The system geometry, potential field, and electron beam steering configure the observability space of the target, which is limited to well-defined regions where the potentials are measured with high accuracy. The analysis provides theoretical and technical insight into the development of future electron-based touchless potential sensing technologies.