NASA's Office of the Chief Technologist (OCT) has begun to rebuild the advanced space technology program in the agency with plans laid out in 14 draft technology roadmaps. It has been years since NASA has had a vigorous, broad-based program in advanced space technology development and its technology base has been largely depleted. However, success in executing future NASA space missions will depend on advanced technology developments that should already be underway. Reaching out to involve the external technical community, the National Research Council (NRC) considered the 14 draft technology roadmaps prepared by OCT and ranked the top technical challenges and highest priority technologies that NASA should emphasize in the next 5 years. This report provides specific guidance and recommendations on how the effectiveness of the technology development program managed by OCT can be enhanced in the face of scarce resources. Table of ContentsFront MatterSummary1 Introduction2 Top Technical Challenges and High-Priority Technologies byRoadmap3 Integrated Ranking of Top Technical Challenges and High-PriorityTechnologies4 Observations and General ThemesAppendixesAppendix A: Statement of TaskAppendix B: Revised Technology Area Breakdown StructureAppendix C: AcronymsAppendix D: TA01 Launch Propulsion SystemsAppendix E: TA02 In-Space Propulsion TechnologiesAppendix F: TA03 Space Power and Energy StorageAppendix G: TA04 Robotics, Tele-Robotics, and Autonomous SystemsAppendix H: TA05 Communication and NavigationAppendix I: TA06 Human Health, Life Support, and Habitation SystemsAppendix J: TA07 Human Exploration Destination SystemsAppendix K: TA08 Science Instruments, Observatories, and SensorSystemsAppendix L: TA09 Entry, Descent, and Landing SystemsAppendix M: TA10 NanotechnologyAppendix N: TA11 Modeling, Simulation, and Information Technologyand ProcessingAppendix O: TA12 Materials, Structures, Mechanical Systems, andManufacturingAppendix P: TA13 Ground and Launch Systems ProcessingAppendix Q: TA14 Thermal Management SystemsAppendix R: Steering Committee, Panel, and Staff BiographicalInformation