Characterization of Simulated Martian Atmospheric Entry Plasma

During entry into the Martian atmosphere the friction between the surface of a probe and the atmosphere will cause thermal ionization of the surrounding air. The plasma parameters associated with this Martian atmospheric entry plasma will vary considerably depending on the spacecraft’s trajectory. The probable range of these parameters was evaluated using the existing Martian atmospheric data and all recorded probe trajectories. Comparison to the existing simulations is discussed. In addition, a desk-top supersonic flow apparatus is devised for the study of aerothermodynamic and chemical properties of a simulated Martian atmospheric gas (SMAG). We performed detailed laboratory measurements of the excited-species populations in the supersonic flow of weakly ionized SMAG. A cylindrical cavity was used to sustain a discharge in SMAG in the pressure range of 100-600 Pa and a stationary acoustic shock wave was generated by an oblique solid body. Excited state populations of Ar were measured using absolute emission spectroscopy. Comparison was made in a model free flow and across the shock front. The gas and electron temperature were determined from the CO rotational spectra and Ar spectra, respectively.