Ground Calibration Method and Experiments of Lunar Surface Dust Sensor in Chang’E-7 Mission

The Chang’E-7 spacecraft is scheduled to be landed in the Aitken Basin region of the lunar South Pole to conduct comprehensive exploration and research on the lunar surface environment. As one of the main detectors onboard the Chang’E-7 spacecraft, a lunar dust detector is developed for in-situ measurements of naturally suspended dust in the polar region, key parameters such as the particle size, velocity, and cumulative mass flux will be obtained. To achieve high-precision scientific detection, systematic ground calibration experiments were conducted. For particle size calibration, a single-particle free-fall method combined with an equivalent test scheme using neutral density filters was employed, achieving coverage of the particle size range from 1 µm to 5000 µm. Experimental results demonstrate that the particle size retrieval error does not exceed 17%. Velocity calibration was performed by measuring the time-of-flight of free-falling particles from different heights, yielding a velocity measurement error within 13%. For mass flux calibration, the solution titration method was used to obtain the sensitivity of the Quartz Crystal Microbalances, with sensitivities in three orthogonal directions all on the order of 10^–9 g·Hz^–1·cm^–2 and exhibiting good linearity. Furthermore, temperature-frequency correction curves were established to support the normalization of in-orbit data. The calibration results indicate that the performance indicators of the dust detector meet the requirements for detection in the extreme environment of the lunar South Pole. The established calibration methods and retrieval models provide a reliable foundation for the interpretation of subsequent in-orbit scientific data.