The U.S. government has taken several steps to account for the increasing likelihood that future conflicts will extend to space, including the establishment in December 2019 of the U.S. Space Force. The potential for future wars to extend to space is driving an urgent need for assessments of space mission assurance (SMA) to provide decision support. Assessments of SMA may be used as decision support for acquisition and operational decisions in the U.S. Department of Defense and intelligence community. The research described in this report was conducted in 2018 and aims to help the national security space community enhance analytic methods for assessing SMA. The authors describe decisionmaker needs for assessments of SMA, challenges for conducting assessments, the shortfalls that may result from the challenges, and options for addressing the shortfalls. The authors conducted semistructured interviews with decisionmakers to identify decisionmaker needs and shortfalls of assessments provided to them in the recent past. Semistructured interviews were also conducted with analysts to identify analytic methods available and to discuss challenges. Researchers examined a selection of models to better understand the capabilities of available analytic methods and their limitations. The research team also undertook its own assessments and modeling efforts to evaluate potential steps and innovations that could address SMA assessment shortfalls.