Lunar Vehicle Active Charge Control System

The specific purpose of this proposal is to develop a prototype instrument called the Lunar Vehicle Active Charge Control System (LVACCS), which will provide an electric potential reference necessary for conventional space plasma instruments to make precise and accurate measurements of charged particles and electric fields within tenuous space plasma environments. This technology is intended to measure the absolute electric potential of a vehicle, discharge any negatively charged vehicle, and safely charge a vehicle to a known positive potential. A similar instrument to the LVACCS is the Charge Control System (CCS) flown on DSCS to mitigate differential charging that spacecraft can experience at geosynchronous altitudes. The CCS consisted of a plasma source, ion and electron electrostatic analyzers, and two surface potential monitors. It weighed roughly 40 lbs, had a volume of 1500 in3, and required 18 W of power to operate. The operational and physical characteristics of the CSS limits its use on rovers and small satellites for lunar missions. Thus, the LVACCS needs to be considerably lighter, smaller, and require less power to operate on a variety of vehicles (e.g. satellites, landers, and rovers) for lunar missions. At the end of this PICASSO study, the final deliverable is a prototype LVACCS instrument that has the capability to measure the absolute electric potential of an electrically isolated test article for both positive and negatively charged conditions in a relevant space environment simulation chamber. The LVACCS has a unique operations concept for each of its multiple use cases, and we discuss two here: positive and negative surface charging states. The LVACCS utilizes a vehicle surface charge detector to sense relative changes in the vehicle potential, and a low-power electron beam to eject electrons in a way that actively changes the vehicle's charging state. When the vehicle is negatively charged, the LVACCS can simultaneously discharge the vehicle using its low-power electron beam and measure the vehicle potential by tracking the change in potential before, during, and after electron beam operations. When enough electrons have been ejected from the vehicle so that the vehicle potential is no longer raised, then the instrument records the total potential difference that was experienced by the vehicle during the electron ejection. On the other hand, when the vehicle is positively charged, the LVACCS can determine the absolute vehicle potential by tracking the changes in potential during electron beam operations at increasingly high levels of beam energy. That is, when the vehicle is charged to a positive potential, the electrons must have a high-enough beam energy to "punch through" the positive sheath and escape without being recollected by the vehicle-induced electric fields that are trying to pull them back in. The proposed work holds significant importance for the objectives of the solicitation and NASA's interests and programs. Scientifically, it will provide an electrical "ground" reference necessary to achieve the science measurement objectives of dust, plasma, and electric field instruments. This is crucial for advancing our understanding of surface boundary exospheres and their time-evolution, thus contributing to both crew safety and science optimization. The LVACCS contributes to both science and planetary protection goals detailed in Origins, Worlds, and Life: A Decadal Strategy for Planetary Science and Astrobiology 2023-2032. It seeks to advance the technology to be used on upcoming missions, especially the SelenITA lunar mission planned to be proposed to PRISM in FY2025 and for other lunar missions (e.g., through the SALSA program) in the future.

This is a mature technology (TRL 7+) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

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