Hayabusa2 Surface and Shock Layer Radiation from the Australian Airborne Observation

Characterization of the radiating flowfield around a spacecraft during its atmospheric entry is of significant value for heat shield design. The reentry of the Hayabusa2 sample return capsule (SRC) was observed from an airborne platform by the Australian Airborne Observation team. This paper reports the extended analysis performed on Hayabusa2 spectral data by converting the data to spectral radiance and emission coefficient, given that the trajectory data of the SRC at each observation point is now available. Attenuation due to atmospheric effects has been accounted for in this analysis with a calculated atmospheric transmission at each trajectory point in time. Surface temperature and its spatial distribution were determined by Planck curve fitting and an empirical temperature distribution model. Surface temperatures varied from 2500 to 3700 K during the measurement. Spectral emission coefficients of atomic lines were calculated taking into account a region of shock layer volume where gas temperature would exceed 7000 K. Presenting the atmospheric-transmission-corrected observation data in spectral radiance and emission coefficient terms eliminates the dependence on the observer’s location for a given view angle, enabling direct comparison with numerical flowfield radiation results.