Preparing for the Dawn mission to Vesta and Ceres

The Dawn project is progressing toward its 2006 launch on a mission to orbit main belt asteroids (4) Vesta and (1) Ceres. Designed to provide insights into important questions about the evolution of the solar system, Dawn will spend more than 0.5 years in orbit about each of these bodies. This challenging mission is enabled by an ion propulsion system. In contrast to missions that use conventional chemical propulsion, the use of this system couples flight system mass and power , thereby requiring different methods of managing these and other technical resources. Now that the project is nearing launch, the refinement of resource estimates allows the identification of excess margin, which is being applied in novel ways to increase the scientific potential of the mission. The unusual relationship of the margins is described, and progress in preparing for the mission is presented.