Contamination Control Approach to Mitigating Radiation Induced Outgassing on Europa Clipper

Abstract

NASA's Europa Clipper mission aims to conduct detailed reconnaissance of Jupiter's icy moon Europa and to investigate whether the moon could harbor conditions suitable for life. To perform these tasks Clipper will carry a suite of state-of-the-art scientific instruments, many of which are susceptible to the effects of molecular contamination and to interactions with the natural Jovian radiation environment. Recent ground testing conducted by the JPL Contamination Control group in the JPL Dynamitron particle accelerator (high-energy radiation source) has demonstrated that many common spacecraft materials exhibit significantly increased rates of molecular outgassing under exposure to high-energy radiation characteristic of the Europan environment [1]. This includes materials to be used in Clipper's thermal blankets and solar arrays, and subsequent free-molecular transport analyses showed that the increases in expected outgassing attributable to radiation would lead to exceedances of molecular deposition requirements for several of Clipper's instruments during the planned mission. The JPL Contamination Control group and the Europa Clipper project investigated testing and analysis refines in parallel with project mitigations strategies to protect Clipper's instruments. Refinements included improving the outgassing testing configuration and performing higher fidelity free-molecular flow analyses of instrument interiors. The project mitigations investigated include developing and testing alternate thermal blanket materials with a lower outgassing response under radiation and developing contamination shields that block line-of-sight between outgassing source surfaces and sensitive instrument surfaces. These mitigations were considered and coordinated with the impacted instrument teams such that any updates to the instrument requirements, available operation mitigations, or science robustness could be considered holistically. A combination of these strategies applied uniquely to each instrument proved most effective at mitigating predicted increases in molecular deposition caused by radiation induced outgassing. This approach demonstrates a novel method of identifying, assessing, and mitigating radiation induced outgassing that will be relevant to future space exploration missions with exposure to high-radiation environments.