Calculating reserves on schedule-to-go (STG) based on historical data

NASA Center guidance typically requires that a mission hold increasing schedule reserves on schedule-to-go (STG) as the project matures. This approach makes intuitive sense as history has shown that project development schedules typically grow beyond their initial planned schedule. This fact begs the question, are the schedule reserve guidelines adequate relative to the experience of historical missions? This study examines current schedule guidelines and actual historical mission data. Additionally external factors that have caused schedule growth are considered and adjustments are made for them. The results can potentially be used to inform NASA Center and Headquarters guidelines for reserves on STG to set more robust guidance for future missions.