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Calibration of an Optical Sensor for Lunar Dust Measurements: Atmospheric and Vacuum Conditions
ABHAY VIDWANS, Brad Jolliff, Jeffrey Gillis-Davis, Pratim Biswas, Washington University in St Louis
Abstract Number: 677
Working Group: Instrumentation and Methods
Abstract
Lunar dust is a major obstacle to future lunar missions. Anticipated issues include visual obstruction, settling onto sensitive power and optical components, and inhalation hazards. To properly mitigate these issues on future missions, NASA has identified submicron dust characteristics as a key target for investigation [1]. Dust concentrations and size distributions near the lunar surface area remain poorly understood, despite several, primarily high-atmosphere, missions [2]. In addition, a spatiotemporal variation of dust characteristics is anticipated due to the highly transient plasma environment of the Moon, causing size and charge-dependent particle lofting and levitation [3]. Measurement of near-surface particles requires a precise, low-cost sensor, capable of measurements in both a vacuum and pressurized environment, to characterize dust in the natural lunar environment and in the pressurized environment where the inhalation hazard exists.
In this study, a low-cost optical sensor (Sharp GP2Y1010AU0F) is calibrated to measure aerosolized lunar simulant concentrations and size distributions at both atmospheric and vacuum pressures. In the first aim, the sensor is placed in two atmospheric-pressure chambers of different volumes filled with aerosolized lunar simulant (JSC-1A). A GRIMM particulate monitor is connected to each chamber to provide reference mass concentrations and size distributions. In the second aim, the sensor is calibrated in a cylindrical vacuum chamber, capable of reaching 10-6 Torr. A dust sample is aerosolized using intense pulses of a He-Ne laser. A SEM stub is placed underneath the sensor as the reference for total integrated particles counted and size distribution. Sensor output readings are correlated against the reference readings to assess the ability of the low-cost sensor to retrieve these critical lunar dust characteristics in-situ.
[1] Winterhalter, D., Levine, J. S., & Kerschmann, R. L. (2020). Lunar Dust and Its Impact on Human Exploration: A NASA Engineering and Safety Center (NESC) Workshop.
[2] Horanyi, M., Sternovsky, Z., Lankton, M., Dumont, C., Gagnard, S., Gathright, D., ... & Wright, G. (2014). The lunar dust experiment (LDEX) onboard the lunar atmosphere and dust environment explorer (LADEE) mission. Space Science Reviews, 185(1-4), 93-113.
[3] Colwell, J. E., Batiste, S., Horányi, M., Robertson, S., & Sture, S. (2007). Lunar surface: Dust dynamics and regolith mechanics. Reviews of Geophysics, 45(2).