Trajectory Estimation of the Hayabusa Spacecraft During Atmospheric Disintegration

The Hayabusa spacecraft was intentionally destroyed in the atmosphere at superorbital velocity at the conclusion of its asteroid sample return mission in June 2010. This study uses single-station ground-based video observations of the reentry to analyze the breakup of the spacecraft and estimate the trajectory of 80 individual spacecraft fragments. An extended Kalman filter with batch initialization is used to estimate the position, velocity, and aerodynamic ballistic coefficients of the fragments. The breakup is characterized and compared with preflight predictions. A high area-to-mass object is seen early during the reentry, which matches closely with the predicted solar panel separation. Nearly all fragments have decreasing freestream dynamic pressure during their observed trajectories. Fragments with high drag ballistic coefficients are more likely to be observed early in the reentry. Assuming simple aluminum spheres, the estimated ballistic coefficients show that the fragments would have radius and mass on the order of centimeters and grams, respectively. The ablation coefficient is also calculated for several fragments using the estimated velocities and ballistic coefficients; results resemble natural meteors and agree with other studies of the Hayabusa reentry using different methods.