Evolution of plasma species and heat – shield temperatures from Hayabusa Reentry Observation

Evolution of plasma species and heat – shield temperatures
from Hayabusa Reentry Observation

Emission signatures of the Hayabusa capsule reentry, acquired by the Australian Ultraviolet Spectrograph instrument on the NASA DC-8 mission over the South Australian Woomera landing site on 13 June 2010, are analysed to identify thermal characteristics of the shock layer and the ablative heat-shield performance. The spectral range 330 to 470 nm of the Australian Ultraviolet Spectrograph instrument contains signatures of the air plasma species nitrogen and the ablation-related species cyanogen. The time-resolved evolution of averaged species number densities, vibrational and rotational plasma temperatures, and the heat-shield surface temperature are deduced through a multiparameter error-minimization analysis based on the European Space Agency plasma radiation database PARADE. The plasma temperatures indicate nonequilibrium conditions for cyanogen at altitudes above 70 km and equilibrium conditions after peak heating. Two separate thermal protection system activity periods are identified by the analysis. Early pyrolysis activity is indicated by a peak in cyanogen and nitrogen – hydrogen emissions at altitudes around 80 km. Broader peaks in the number of cyanogen molecules and reduced nitrogen – hydrogen emissions were identified around the time of peak heating at an altitude of about 57 km and elevated surface temperatures, above 3000 K.

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