Analysis of the JAXA Nonequilibrium Infrared Emission Spectra for Mars Entry Conditions

International audienceNonequilibrium infrared emission spectra representative of a Mars atmospheric entry mission are modeled using RADIS, a spectral code for CO and CO 2 based on the HITEMP-2010 and CDSD-4000 databases. The modeled experimental data for the free-flow and the forebody radiation were obtained in the JAXA expansion tube facility. In the expanding flow, good agreement with the experimental data can be obtained using a slightly nonequilibrium distribution and a homogeneous flow. The model suggests that all three CO 2 vibration modes share a same vibrational temperature slightly higher than the gas temperature. In the shock layer, the forebody radiation includes both CO 2 and CO emission features. It can be correctly predicted by assuming thermal and chemical equilibrium at 4000 ± 500 K. Nomenclature p = pressure [bar] T r ot = rotational temperature of the gas [K] T tr ans = translational temperature of the gas [K] T vib = vibrational temperature of the gas [K] T vib 1 , T vib 2 , T vib 3 = for CO 2 , temperature of each vibration mode: symmetric, bending and asymmetric vibration, respectively [K] x CO , x CO