Deep Impact, the mission

This paper discusses the Deep Impact (DI) mission (the 8/sup th/ Discovery Mission) objectives and potential discoveries derived from impacting a comet nucleus at ten times the speed of a bullet and simultaneously observing the results of that impact. The scientific return from this mission centers on 13 minutes of critical operations while flying through a comet's coma on July 4, 2005. A detailed mission and spacecraft description is provided including science instruments. The overall implementation approach is discussed, including the special shared development and operations responsibilities among JPL, Ball Aerospace and University of Maryland. This paper also discusses the unique challenges of this mission especially the unknowns and potential hazards of flying deep into the comet environment (e.g. dust, surface topography, structure and composition). The design for robustness in the face of significant unknowns is discussed including autonomous navigation to track and hit a target, at a relative speed of 10 km/s.