Development of a Monte Carlo Overlay Method with Application to Spacecraft Glow

Brightness calculations for visible emissions from nitrous oxide, known as a spacecraft glow, around the Atmospheric Explorer (AE) satellite are presented over an altitude range of 140-180 km. The flowfield is determined using the direct simulation Monte Carlo method. A novel overlay technique is developed to capture the microscopic behavior of rare atmospheric species, such as nitric oxide. A simple model for glow is proposed, identifying nitric oxide as the important species in the gas-phase controlling flow brightness. Sensitivity to altitude and to different chemical reaction cross sections for nitric oxide production is assessed. The importance of nitric oxide production is found to be greatest at lower altitudes. At higher altitudes, the ambient concentration of nitric oxide is the critical factor in determining glow brightness. Comparison of the results with measurements from the AE indicates an efficiency of approximately 0.01 for producing the excited state of nitrous oxide from nitric oxide impacting on the vehicle surface. (Author)