Abstract: In order to study the law of LEO satellite spin motion, for the LEO satellite whose ascending node right ascension precesses slowly, its attitude motion model under the influence of gravity gradient torque was established. Besides, the analytical solutions of the precession angle, nutation angle and spin angle were derived when the spin angular rate met certain conditions. Also, the correctness of the analytical solutions was verified by simulation results. In the circumstance that the orbital plane precesses slowly, when the satellite spins around the maximum principal inertia axis, the value range of the spin angular rate was given, and within this range, the spin motion of the satellites can precess with the orbital plane simultaneously, the spin axis can precess at a constant average angular rate, and the nutation angle fluctuates on small scales. When the attitudes of the nearEarth satellites are out of control, the established model on the attitude motion of spinning as well as the analysis conclusions can be used to estimate and predict the attitude. They can also be used for the design of ontrack attitudes as well as ontrack backups.

Key words: LEO satellite, gravity gradient torque, perturbed orbit, spin attitude motion；attitude determination