Speaker
Description
Modification of thermal control surfaces is still a big uncertainty for lunar surface missions. For thermal engineers, changes in thermo-optical properties over mission lifetime can be crucial for thermal design feasibility. Literature from measurement campaigns shows a significant increase especially of radiator coatings’ solar absorptivity. The shortcoming of legacy measurements is their focus on dust coverage rate in % and obviously they are conducted exclusively with lunar dust simulants (LDS). In contrast, simulations and measurements of natural dust coverage rates are usually provided in mass deposition per area. Hence, there is a missing link between the changes in thermo-optical properties and the dust coverage rate caused by natural and anthropogenic processes.
A recent measurement campaign conducted by ONERA under an ESA contract in the scope of the ESA Argonaut program, established a correlation between dust coverage in % and dust deposition in mass deposition per area for the LDS LHS-1 and LHS-1-25A via hundreds of measurements for various thermal control surfaces.
Based on the ONERA measurements, a theoretical approach was derived which accounts for differences in particle size distribution, particle shapes and thermo-optical properties between LDS and natural regolith. The result of this approach is a set of equations that empirically links dust coverage in mass deposited per area for real regolith with predictions of modification factors for thermal control surfaces. The approach and results for a selection of coatings will be presented at the workshop.
