Emission spectroscopy and surface temperature analysis from Hayabusa2 sample return observation

Remote observation is an important way for studying the re-entry environment that a spacecraft experiences. On 5 December 2020 UTC, researchers from the University of Queensland (UQ) took part in the flight observation of the Hayabusa2 Sample Return Capsule's re-entry, conducting independent measurements alongside other research teams. The UQ system, which included a tracking camera and two grating prism spectrometers, was designed to capture atomic transitions of nitrogen, oxygen, and hydrogen, as well as blackbody radiation, in the visible and near-infrared regions. Spectra were recorded from 17:28:56 to 17:29:16 UTC, with data from 17:28:56 to 17:29:08 UTC successfully processed and calibrated, covering the peak radiative heating point at 17:29:03 UTC. This paper outlines the data processing and calibration techniques, including methods for extracting spectra in low signal-to-noise ratio images and correcting for spectral blurring across spatial dimension. Calibrated spectra are presented, and surface temperatures were derived by fitting the spectra to Planck's law. UQ's data, as an important subset of the broader dataset from the joint observation, showed strong agreement with the results from other teams during the overlapping time frames. The fitted temperature profile also aligned with numerical predictions.