Development of Spacecraft Molecular Accumulation and Contamination Kinetics Simulator (SMACKS)

The Near-Earth Object Surveyor (NEO Surveyor) mission is a 50 cm diameter infrared telescope capable of detecting asteroids which will help advance NASA's planetary defense efforts to discover and characterize potentially hazardous near-earth objects in our solar system. As an infrared observatory, NEO Surveyor's sensitive optical surfaces and radiators operate at temperatures <60K, which can readily collect significant amounts of contamination and lead to performance degradation if not properly mitigated via material selection, bakeouts, thermal control and mechanical design. The most critical on-orbit portion of NEO Surveyor's contamination control strategy is during the initial period after launch when surfaces are warmest, leading to the highest outgassing rates. After an initial decontamination period, the optics are cooled down to their cryogenic operational temperatures which leads to a highly transient thermal profile for both outgassing sources and sensitive surfaces. In order to model the contamination collection during this period, a novel Python-based contamination analysis tool entitled “Spacecraft Molecular Accumulation and Contamination Kinetics Simulator” (SMACKS) was developed and tested. This Python-based tool is an evolution of previous workbook-based models such as those applied to NASA's Psyche and Lunar Gateway programs. Compared to earlier models which performed simplified steady state calculations with limited abilities to account for temperature-dependent outgassing rates, SMACKS allows for evaluation of fully transient thermal profiles, inclusion of detailed material outgassing data sets, and automated creation of results visualizations. In addition, the Python-based tool is more robust to user-error as it requires significantly fewer manual inputs and manual inspections/testing than the workbook models. This work describes the development, testing and application of SMACKS for the NEO Surveyor mission, and discusses future applications and enhancements of the code.