Modification of Thermal Control Surface Thermo-Optical Properties by Lunar Dust – an Empirical Approach for Thermal Engineers

Modification of thermal control surfaces remains a large unknown for the thermal analysis and design of upcoming lunar surface missions. In literature, so far there is no measurement-based correlation between lunar dust deposition rate [µg/cm2/year], dust coverage rate [%], and the modification of solar absorptance and infrared emissivity for lunar regolith. In this paper this gap is addressed with an empirical approach that allows linking deposition rates for real lunar regolith to the degradation of 20 different thermal control coatings. The approach is using a combination of modelling techniques and a large data set of measurements conducted with lunar dust simulants. The model facilitates material properties, shapes of dust grains and the particle size distribution. The measurement data of lunar dust simulants serves as basis to correlate the model. Based on the correlation, an extrapolation to real lunar regolith is performed, with different particle densities, and size distributions. As a result, an empirical trendline is established for the modification of solar absorptance and infrared emissivity by real lunar regolith, linking it to dust coverage in [µg/cm2] as well as area coverage [%]. Assumptions and limitations of the approach are highlighted and discussed. The work is intended to support thermal engineers in sizing of thermal hardware and spacecraft for lunar surface missions.