Calibration and Evaluation of a Low-Cost Optical Particulate Matter Sensor for Measurement of Lofted Lunar Dust

Several recent Earth-based investigations employed low-cost particulate matter (PM) sensors to address the lack of spatiotemporal resolution in air quality data. The lunar environment also has a PM problem in the form of fine lofted and levitated dust particles. Natural and anthropogenic mobilized dust can cause a slew of difficulties for surface operations (deposition onto radiators, optical components, and mechanical devices). Despite the urgency of mitigating dust on the Moon and other airless bodies, the performance of low-cost sensors has not been critically evaluated for space applications. Upcoming long-term robotic and human exploration missions to the Moon necessitate a robust sensor that can monitor PM levels and establish a spatially and temporally resolved global network. In this work, we calibrate two optical light-scattering PM sensors against research-grade aerosol instruments for measuring the concentration of aerosolized lunar simulants. Sensors showed a stronger dependence on aerosol particle size distribution than particle composition. Vacuum testing showed a significant deviation in performance compared to atmospheric pressure, with a stronger dependence on lunar simulant. The predicted mass deposition, based on sensor output coupled with dust trajectory, was within an order of magnitude of the reference deposition. Our results demonstrate for the first time that low-cost PM sensors can monitor dust concentrations with reasonable accuracy in a vacuum environment, with two caveats. First, precise calibrations must be performed with a dust simulant closely matching the particle size distribution of the target dust, and second, atmospheric pressure calibrations alone are insufficient.