Hayabusa2 Capsule Reentry: Visible and Near-IR Emission Spectroscopy from the Australian Airborne Observation

This paper presents the data collected from four spectrometers by the Australian Airborne Reentry Observation Mission for the Hayabusa2 capsule reentry, which occurred on December 5 2020 UTC. The Australian Airborne Observation provided a largely side-on view of the Hayabusa2 reentry, data which can complement the data collected from the more front-on view from other observations. The instrument calibrations are presented and revisions made to previously published background subtraction and region-of-interest identification. A Planck curve fit is used to determine the apparent blackbody temperature of the Hayabusa2 capsule surface. This fitting routine is completed for data with and without an estimated correction for atmospheric transmission effects for a 22 s period of the reentry. Using the estimated atmospheric correction, the peak apparent capsule temperature was approximately 3200 K. Useful data was acquired for approximately 13 s after this peak value, after which time the apparent temperature reduced to 2200 K. Preliminary analysis of the shock layer emission through investigation of the strength of the molecular oxygen 777 nm emission has demonstrated a capacity for defining the temporal evolution of shock layer emissions.