over to nominal operations and began making our groundbreaking science observations. Remarkably, the IBEX project was able to do all this work including developing an entirely new launch capability, building and ying a unique and highly specialized spacecraft and instrument suite, and maintaining full funding for our Education and Public Outreach and Phase E science activities, while still under-running our original cost cap (as modi ed by NASA-directed changes), by roughly three-quarters of a million dollars. This book comprises a set of papers that describe the IBEX science, instruments, and mission and put these in the context of the existing knowledge of the interstellar interaction at the time of the launch. The book sets the stage for research that will be based on data from the IBEX mission. We sincerely hope that future researchers, authors and students will use this information to help in their studies. Chapter 1 [McComas et al. ] provides an overview of the entire IBEX program including the IBEX science, hardware, and mission. Chapter 2 describes the IBEX spacecraft and ight system [Scherrer et al. ]. Chapters 3–4 provide the details of the IBEX-Hi instrument [Funsten et al. ] and background monitor that is built into it [Allegrini et al. ], while Chapters 5–7 describe the IBEX-Lo instrument [Fuselier et al. ], how IBEX-Lo can measure the interstellar neutrals directly entering the heliosphere [Möbius et al.