Balance in NASA's Space Science Program and the Roles of Extended Missions and Large Strategic Missions

摘要

Decadal surveys are a signature product of the U.S. National Academies of Sciences, Engineering, and Medicine and the foundation on which NASA's space science exploration program is founded. The surveys have a reputation as credible and unbiased science assessments and prioritization in each of the space sciences. A major theme in each survey is the maintenance of a "balanced" program across the relevant discipline. One important element of balance is the tension between developing new science missions and extending the support of missions that have proposed science goals beyond their primary phase of operations. Another element of balance is the appropriate role and "share" of the overall program that is carried out between larger strategic class missions-sometimes called "flagship" missions-and medium-sized and smaller missions. The Space Studies Board (SSB) of the National Academies recently released a study NASA Extending Science: NASA's Space Science Mission Extensions and the Senior Review Process. The report evaluates the scientific benefits of missions extensions, the current process for extending missions, the balance between starting new missions and extending operating missions, and makes recommendations based on this review. In addition, the SSB released a new report in the summer of 2017 following a study carried out by the Committee on Large Strategic NASA Science Missions: Science Value and Role in a Balanced Portfolio. That report examines the role of large strategic missions within a balanced program across NASA Science Mission Directorate (SMD) space and Earth sciences programs. The report considers the role and scientific productivity of such missions in advancing science, technology and the long-term health of the field, and provide guidance that NASA can use to help set the priority of larger missions within a properly balanced program containing a range of mission classes. This paper presents an overview of these two U.S. National Academies rep