Near Earth Objects, our Celestial Neighbors: Opportunity and Risk Proceedings IAU Symposium No. 236, 2006 A. Milani, G.B. Valsecchi & D. Vokrouhlick´ y, eds. c  2007 International Astronomical Union doi:10.1017/S1743921307003213 The Dynamics of NEO Binary Asteroids D.J. Scheeres Dept. of Aerospace Engineering, The University of Michigan, Ann Arbor, MI 48109-2140, USA, email: scheeres@umich.edu Abstract. The dynamics of binary Near-Earth objects (NEO) are discussed and a simple model for the study of their dynamics is introduced. Main results on the motion and stability of binary asteroids are reviewed. The effect of perturbations external to the binary system, including solar gravity, solar radiation pressure, and planetary gravity, are considered. Keywords. asteroid, rotation; dynamics, rotation; binary asteroids 1. Introduction Binary NEO exhibit a rich set of dynamics and are exposed to many external and internal perturbations. These include coupling of orbital and rotational angular momen- tum and energy, effect of non-spheroidal mass distributions on dynamical evolution, solar gravitational perturbations for bodies close to the sun, planetary tides during close ap- proaches, and Solar irradiation effects. The general dynamical problem of binary asteroids, or binary bodies in orbit about each other and subject to external perturbations, has received considerable study over the years. The relevant studies include investigations of point mass dynamics about non-spherical bodies Chauvineau et al. (1993), Scheeres (1994), Scheeres et al. (1996), Scheeres et al. 1998, point mass dynamics about point bodies incorporating solar gravita- tional and radiation perturbations Hamilton & Burns (1991), Scheeres & Marzari (2002), effect of solar radiation on finite bodies ´ Cuk & Burns (2005), motion of two massive bod- ies about each other Kinoshita (1972), Maciejewski (1995), Scheeres (2002a), Scheeres (2002b), Breiter et al. (2005), and motion of particles about binary asteroids Scheeres & Bellerose (2005). Recently, a detailed model and associated dynamics of the NEO binary asteroid (66391) 1999 KW 4 was studied in detail in Ostro et al. (2006), Scheeres et al. (2006). Despite these many studies the general problem still has many challenges that must be addressed, ranging from better constraints and understanding of the dynamical evolution of these systems to basic questions on what the most important physics for the evolution and energy dissipation of these systems are. The goal of the current paper is simply to define the basic dynamical problem of binary asteroids, introduce an ideal model for binary asteroids and present basic results on its dynamics, and identify the most relevant known perturbations acting on these systems and their characteristics. 2. The General Model We first state the most general form of the binary asteroid dynamics problem. These have been derived in an alternate form in Maciejewski (1995) and provide the equations of motion for the relative translational motion between the two components of the binary asteroid and each body’s rotational dynamics. We give the current statement as they are 177