This book provides information on the planned National Polar-orbiting Operational Environmental Satellite System (NPOESS) program which is expected to be a state-of-the-art, environment-monitoring satellite system which will replace two existing polar-orbiting environmental satellite systems. The NPOESS program is considered critical to the United States’ ability to maintain the continuity of data required for weather forecasting (including severe weather events such as hurricanes) and global climate monitoring through the year 2026. Furthermore, this book evaluates the NPOESS program office’s progress in restructuring the acquisition, evaluates their progress in establishing an effective management structure, and assesses the reliability of the life cycle cost estimate and proposed schedule. This book also identifies the status and key risks facing the program’s major segments and evaluates the adequacy of the program’s efforts to mitigate these risks.