Observation of Electron Density Depletion Due to Maneuver Operation of H-II Transfer Vehicle

摘要

The plasma sensor on the sixth H-II Transfer Vehicle (HTV) measured the depletion of electron density during some maneuver operations for attitude or altitude control. In this paper, we first discuss the on-orbit observation of electron density depletion during the entire lifetime of the HTV. On-orbit data showed that both altitude and attitude control maneuvers caused the depletion effect. The geocentric coordinates and universal time were also shown to confirm the depletion effect around the HTV by using other techniques, such as total electron content based on the Global Navigation Satellite System network. In the latter part of the paper, we discuss the cause of the depletion effect based on past literature. To analyze the interaction between thruster plume gas and ionospheric plasma, computational fluid dynamics simulations were conducted to analyze the number density distribution of molecules around the HTV. It was found that the combination of charge exchange and dissociative recombination possibly caused the depletion of electron density during altitude control maneuvers, due to neutral particles being ejected from the thrusters and a time delay in the reaction response. During attitude control maneuvers, the electrons of ionospheric plasma were pushed away from the plasma sensor by dense neutral clouds.