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A new method for the identification of the peak temperature of the heat shield based on remote spectral irradiance measurements is proposed and tested through the analysis of results from the Hayabusa sample return capsule. To identify the peak temperature of the heat shield, a parameterized empirical model for the surface temperature distribution on the geometry is developed, and it is then used to simulate spectra for optimized fitting with a measured spectral radiance. This new peak temperature identification method is shown to be insensitive to the wavelengths resolved, the view of the geometry, and measurement noise. The peak temperature of the Hayabusa capsule geometry at the representative condition considered (3330 K) was resolved to within 20 K for the three instruments investigated, while the effective temperature varied by around 600 K depending on which instrument was used. The error in the peak temperature model is also shown to be an order of magnitude less sensitive to measurement noise than the effective temperature approach. The new peak temperature method facilitates the direct comparison of results from instruments with different bandwidths and/or different view angles of the capsule, which was previously not possible. [ABSTRACT FROM AUTHOR]

The reentry trajectory of the Hayabusa2 capsule has been measured using a single video stream captured during the Australian Airborne Observation of the Hayabusa2 capsule. A new analysis methodology was required, and developed, to enable the trajectory to be determined from a single viewpoint. The method developed used the star-field background visible in the video stream, combined with the aircraft Global Positioning System data, to establish lines of sight along which the capsule was measured in time. A set of common sense criteria including altitude and velocity limits were then used to exclude impossible trajectories. The remaining trajectories were then examined and evaluated using a least-squares fitting routine to analyze candidate ballistic trajectories. The trajectories were ranked based on the fit parameter, enabling the determination of the single most likely trajectory and a family of most probable trajectories. The most probable Hayabusa2 capsule trajectory inferred from the measurements passed 10 km west of Coober Pedy and traveled at a heading of 150 deg. Evaluation of other highly probable trajectories showed they all passed Coober Pedy at a similar distance; however, they tended toward a slightly higher heading, approaching 155 deg. The distance between the measurement aircraft and the capsule remained relatively constant at approximately 180 km throughout the measurement period. This work demonstrates a new method for determining the trajectory of an object measured with a star-field background. Importantly, we have used this to establish the Hayabusa2 reentry capsule trajectory, and hence the distance from our aircraft, which will allow the detailed analysis of our spectral data. [ABSTRACT FROM AUTHOR]