The Europa Clipper space environments test campaign has made extensive use of the Dynamitron electron accelerator located at the Jet Propulsion Laboratory. One of the most common uses of this facility has been gathering data on the internal electrostatic discharge (IESD) properties of the various elements of the spacecraft. These testing needs often required some reconfiguration of the accelerator system. One of the most recent upgrades was adding the ability to measure both dark conductivity and radiation-induced conductivity (RIC) for spacecraft materials. Adding this new one-of-a-kind capability required incorporating a low-energy electron flood gun to the existing higher energy electron beam from the Dynamitron accelerator. The upgraded system was also designed to obtain data on multiple samples per test run allowing for the acquisition of a large quantity of data in a relatively short time period. Dark and radiation-induced conductivities measured using the new system are provided demonstrating examples of results that can be obtained.

Space charging of dielectrics results in the build-up of electric fields between the trapped charge (typically electrons) and image charges in nearby conductors. Engineering assessments are typically concerned with the magnitude of the electric field relative to a discharge threshold. The same electric field, however, also results in strong electrostatic attraction. For rigid dielectrics (such as solar cell coverglasses, second surface mirrors, or printed circuit boards), the electrostatic forces have no consequences. But for lightweight flexible dielectrics, the electrostatic forces can lead to static cling. A simple 1-D analysis of the electrostatic force between trapped and image charges is presented, and the phenomenon is demonstrated by ground test video. The electrostatic force is sufficient to overcome the Earth’s gravitational force. The video shows significant movement in a single-layer thermal blanket of a periodic nature. As the material reaches a sufficient charge level, the electrostatic forces begin to dominate and the material starts moving until it makes contact with the ground plane, discharges, and the cycle begins again. Without the vacuum-deposited aluminum (VDA) layer on the Kapton film, the static cling would be permanent.

Spacecraft interacts with the charged particles of the space environment, leading to their electrostatic charging. This charging depends on the surface materials and their exposure to space. Thus, it is different for different parts of the spacecraft. This differential charging is particularly important on solar panels, which are composed of various polarized elements juxtaposed over small distances. This leads to strong electric fields ultimately leading to electrostatic discharges (ESDs), themselves being the onset of destructive secondary arcs. Hence, controlling the onset of ESDs is a key factor to prevent damages on spacecraft. Two ways are generally envisioned to act on the ESD onset: the geometry of the solar cells and the material electrostatic properties. In this article, the control of the ESD onset is tackled through the study of the effects of the cover glass secondary emission properties on the voltage threshold of solar cell ESDs. This study is conducted numerically with the spacecraft plasma interaction software (SPIS)-ESD software, as the natural variability of physical samples and the impossibility to have materials with controlled characteristics render the experimental study unpractical, if even feasible.