Milankovitch equations with spinors

We investigate the use of spinors to describe the secular evolution of quasi-Keplerian systems. Evaluating their Poisson brackets, we show that the components of a properly chosen spinor are canonical variables. We illustrate this formalism using the classical problems of the orbital motion about an oblate planet and the Kozai-Lidov mechanism. Although the present formalism breaks down for circular or radial orbits, it may be of some practical utility in numerical recipes.