Understanding how solar wind charges lunar spacecraft

Gateway, a planned space station that will orbit the Moon as part of NASA’s Artemis program, will house humans alongside scientific experiments. The Heliophysics Environmental and Radiation Measurement Experiment Suite (HERMES) is one such experiment aimed at understanding solar wind and observing local space weather to support human exploration in deep space.

When HERMES’s electron electrostatic analyzer (EEA) collects electron flux data to help understand and predict space weather events, this data is contaminated by electrostatic charging effects on Gateway itself, which must be corrected. Bengtson et al. addressed this problem and developed a way to use the electron flux data to study the electric potential on the spacecraft.

“Gateway itself locally changes the space plasma we want to measure,” said author Miles Bengtson. “Knowledge of the spacecraft potential would allow us to remove these effects and measure the plasma.”

The researchers simulated the interactions between the EEA and solar wind and created maps of what EEA will measure under different solar wind conditions. Due to Gateway’s unique design, they expect the surfaces to charge negatively in the solar wind.

With upcoming plans to return humans to the Moon, these simulations can provide a foundation for understanding the local space environment.

“Future missions need to be intelligent and clever, so it is exciting to advance the state of the art by developing techniques that squeeze the most amount of insight out of the dataset,” said Bengston. “I hope our findings can support the successful long-term operations of humans in lunar orbit, to the lunar surface, and beyond.”

Source: “Use of low-energy electron measurements to determine charging on lunar gateway,” by Miles T. Bengtson, Alexander C. Barrie, Daniel J. Gershman, and William R. Paterson, Physics of Plasmas (2025). The article can be accessed at https://doi.org/10.1063/5.0258247 .