A Monte-Carlo simulation of single-line resonant scattering in a rarefied gas is presented and the technique is applied to the interpretation of a rocket-borne resonance-lamp experiment. The simulation examines the case of an emitting and absorbing gas at the same temperature for a number of detector and source configurations. The distance from the last scatter point, the angular distribution of the detected scattered photons, and the line shape formed by the scattered photons, at the detector, are evaluated for these different configurations. The simulation results suggest that the scattering of the detected photon occurs very near to the rocket, and not necessarily in the traditional scattering region at the intersection of the detector and emitter normals. It is observed that multiple scattering plays an important role in the number of photons detected and that the apparent gas temperature, as exhibited by the line shapes of the scattered photons, is dependent upon the configuration of the experiment. The simulation results suggest that, for a resonance-scattering experiment to measure constituent concentrations, the experimental design must optimize the return signal and minimize the effect of multiple scattering. The results also suggest that the calibration procedures for resonance-scattering experiments must be made with a physical configuration and environment that is identical to that expected in the rocket flight.
A suppressive effect of rarefied gas flow through a circular orifice caused by temperature increase of the orifice plate (The unsteady approach and the direct Monte-Carlo simulation)