Optical monitoring of the dust environment at lunar surface exploration sites

Abstract

Lessons from the Apollo program showed that dust perturbed by human activities on the lunar surface can significantly interfere with the operation of mechanical, thermal and optical systems. During the Artemis program, monitoring the local dust environment created by surface activities will be critical to understanding and mitigating problems associated with lunar dust. This could be accomplished at many locations using in situ dust detectors; however, a complementary, and arguably more comprehensive, approach would be to measure the intensity of scattered sunlight from dust. Such measurements could be obtained using modest cameras and yield the abundance of dust along an observer line-of-sight. Observations along several look-directions would reveal the dust spatial distribution and constrain the minimum grain size from the angular width of the forward scattering lobe. Perhaps most importantly, these measurements would constrain spatial and temporal variations in dust ejection and deposition rates. Using scattering properties for realistically shaped lunar dust grains, this study simulates spectral intensities for a plausible steady-state distribution of low-speed (∼ m s−1) dust around an exploration site. This is used to assess the feasibility of using commonly available wide-angle optics and commercial off-the-shelf (COTS) image sensors to create a notional dust monitoring camera. The dust detection sensitivity of cameras constructed using components with flight heritage is modeled; e.g., the PL1 image sensor aboard the Light Italian CubeSat for Imaging of Asteroids (LICIACube) part of NASA's Double Asteroid Redirect Test (DART) mission. Results indicate that a simple but well-baffled camera can successfully detect a steady-state dust cloud created by human (artificial) activity with a peak concentration of < 1 μg m−3 for a polar site on the Moon—well below what might be expected during Artemis operations.