AAS 13-259 COMET THERMAL MODEL FOR NAVIGATION Pedro J. Llanos ∗ , James K. Miller † , Gerald R. Hintz ‡ We implement a numerical model to analyze the thermodynamics that can be used for navigation and orbit determination of future space missions to small bodies. Unlike past models that use a spherical homogeneous model, our model includes the real non-spherical shape of asteroid 433 Eros. The surface temperature map is expressed as a function of latitude and longitude directions for different initial isothermal temperatures. The lack of spherical symmetry is modeled along with the long and short term temperature variations as a consequence of the orbital and spin axis rotations of the body. INTRODUCTION In 1986, Giotto encountered comet Halley to explore some of the most ancient materials of the solar system. Over the past decade, there has been a growing interest in describing the atmosphere in the vicinity of comets. Past NASA missions to small bodies include the NEAR rendezvous and first landing on asteroid Eros 433 in February 2000, Deep Space 1 entering the coma of comet 19P/Borrelly in September of 2001, and Stardust/NExT entering the coma of comet P/Wild 2 in 2004 and then flying by Comet Tempel 1 on 14 February 2011. Other missions include the JAXA Hayabusa mission’s encounter with the asteroid Itokawa in September 2005 and the ESA/NASA Rossetta mission’s expected rendezvous with comet 67P/Churyumov-Gerasimenko in May 2014. Rosetta will release its module Philae, which will attempt to perform the first controlled landing on the surface of a comet to study the development of cometary activity and the interaction of the dust and gas in the inner coma. In 1950, Whipple 6 revolutionized our cometary knowledge when studying the non-gravitational acceleration of comet Encke. Whipple’s theory of comets not only explains the physical and chem- ical features but also the origin and the non-gravitational effects of forces acting on these small bodies. Comets have very eccentric orbits so, when they approach perihelion, the ice on the surface vaporizes. The solar heat may also heat the outer parts of the comet and transfer into the inner parts of the nucleus. During this heating and vaporization process, some volatile inner material (water vapor) is released to form an expanding atmosphere which carries dust. The sublimated ice leaves behind large particles of non-volatile elements which forms a mantle. The cometary outgassing accelerates the spacecraft and is similar to the acceleration from non-gravitational effects such as solar radiation pressure, gas leaks and spacecraft outgassing. In this paper, we will analyze the * Marie Curie Experienced Researcher Fellow, Flight Mechanics Group, GMV Space and Defence, S. A., Tres Cantos, Madrid, Spain, 28760, Member AIAA. † Navigation Consultant, Associate Fellow AIAA, Los Angeles, CA, 91326 ‡ Adjunct Professor, Astronautical Engineering Department, University of Southern California, Los Angeles, CA, 90089, Associate Fellow AIAA 1