Titan Atmosphere Plasma Characterization Using Spectroscopic Measurement Techniques

Abstract

During Titan atmosphere entry, the heat shield of a planetary exploration vehicle experiences high radiative heat loads. In these conditions, owing to the composition of Titan's atmosphere, the radiative heat flux can be comparable to or greater than the convective heat flux. Therefore, proper design of the heat shield necessitates a good knowledge of the radiative properties of the high temperature gas present in the shock layer. Few experimental data are available on this problem. We present in this study measurements aimed at producing experimental data representative of Titan entry conditions.

Erratum on Spectroscopic Analysis of Titan Atmospheric Plasmas

“…Therefore, for this radial position, a 21% estimated error is obtained for the measurements. Concerning the computations, 5% accuracy is attributed to the transition probabilities of CN [20] and 5% to the equilibrium composition computation [13], leading to a total accuracy of 10%. Those estimates can reasonably account for the observed discrepancy.…”

“…Nevertheless, ICP wind tunnels have demonstrated their use in the validation of plasma emission computation under local thermodynamic equilibrium (LTE) conditions [11] and can provide nonequilibrium conditions for the analysis of collisional energy transfer processes [12]. Emission spectroscopy measurements performed in the VKI Minitorch ICP facility are presented in this paper [13]. The test campaign can be divided in two steps.…”

Plasma radiation for atmospheric entry at Titan: Emission spectroscopy measurements and numerical rebuilding

“…The axial symmetry of the plasma jet has been assessed. Details on the adopted optical arrangement and its calibration procedure in absolute units can be found in Playez et al (2004). Before performing the plasma characterization in terms of temperature, the local emission (in W cm −3 nm −1 sr −1 ) has been rebuilt by means of an Abel transform applied to measured line-of-sight intensity radial profiles (in W cm −2 nm −1 sr −1 ).…”

“…Before performing the plasma characterization in terms of temperature, the local emission (in W cm −3 nm −1 sr −1 ) has been rebuilt by means of an Abel transform applied to measured line-of-sight intensity radial profiles (in W cm −2 nm −1 sr −1 ). The local emission spectra considered in the following have been corrected consistently with recommendations of Playez et al (2004) accounting for calibration uncertainty and plume fluctuations. The temperature was determined through a common fitting approach consisting in the determination of the temperature minimizing the error between the experimental spectrum and spectra simulated at LTE.…”

Quantitative Spectral Radiance Measurements in the HYMETS Arc Jet

“…The relative intensities of these spectra will be discussed in detail in a subsequent section. Identification of atomic and molecular spectra was performed mainly from four different sources: the NIST Atomic Spectra Database, 17 the reference book by Pearse and Gaydon, 18 the thesis of Playez, 19 and the paper by Park et al 20 In Fig. 4, selected bands (usually the lowest vibrational bands) are labeled in the figure with vertical hash marks indicating other bands that have been positively identified.…”