Revisit of rotational dynamics of Asteroid 4179 Toutatis from Chang'e-2's flyby

摘要

This paper presents analysis of the rotational parameters of Toutatis basedon the observational results from Chang'e-2's close flyby. The 3-D shape modelderived from ground-based radar observation is used to calculate the 3-1-3Euler angles at the flyby epoch, which are evaluated to be$-20.1^\circ\pm1^\circ$, $27.6^\circ\pm1^\circ$ and $42.2^\circ\pm1^\circ$. Thelarge amplitude of Toutatis' tumbling attitude is demonstrated to be the resultof the large deviation of the angular momentum axis and the rotational axis.Two rotational periods are evaluated to be $5.38\pm0.03$ days for rotationabout the long axis and $7.40\pm0.03$ days for precession of the long axisabout the angular momentum vector based on Fourier analysis. These resultsprovide a further understanding of rotational state of Toutatis.