This volume aims to be a complete treatment for many elements of space mission design and astronautics. Topics include: extensive coverage of constellation design and management; relative motion of satellites (global, local, at similar and widely differing altitudes); definition of an orbit cost function for comparing the cost of access to and maintenance of alternative orbits; most extensive discussions available of autonomous navigation and autonomous orbit control; a discussion of Earth coverage and viewing and lighting conditions; apparent motion of other satellites needed for cross-link pointing and antenna coverage; analytic expressions for the field of view of an array processor on the celestial sphere and projected onto the Earth's surface; detailed process for creating and analyzing mapping, pointing, and timing budgets; closed-form expressions for the ground track of a circular orbit, including high accuracy approximations for ground station coverage. There are also: convenient formulas for specialized orbits about the Earth and other planets; practical spacecraft problems such as time discontinuities, GPS coverage at satellite altitudes, and how to identify and handle singularities in measurement sets; and new solutions for all possible spherical triangles without quadrant ambiguities and allowing all sides and angles to range from 0 to 360 degrees. The book discusses both the similarities and differences between orbit and altitude systems in terms of hardware, algorithms, design, and processing requirements. With the demand for reduced cost and the introduction of extensive on-board computing, what were once entirely separate disciplines have begun to merge. This volume should speed that process. In all areas, it is meant to be practical, with recommendations, insights, formulas, and numerical recipes based on 40 years of spaceflight experience from organizations worldwide. It is meant to be both a text and reference work that can be used by those entering the field and by senior engineers engaged in the design, analysis, construction, or on-orbit operations of orbit and attitude systems and components.