The purpose of this handbook is to provide guidance for laying out a mission success approach for cubesat missions to cover a range of different mission lifetimes, and independently a range of different criticalities. For example, there may be cases for a very short lifetime mission that is critical (analogous to a launch vehicle placing in orbit a key national asset). The guidance below accounts for the fact that no matter what the criticality or lifetime of the mission, the use of a cubesat brings with it tremendous constraints in size/compactness as well as cost and schedule available, relative to larger missions. This document begins with the assumption that while there may be critical and/or long lifetime cubesats, the A and B classifications applied to larger spacecraft carry with them burdens that currently are not implementable under cubesat constraints even for constellations. The risk postures in this document range from the most common, i.e., "Do No Harm" (highest risk posture) classification through a NASA mission Class C as the lowest risk posture approach addressed in this handbook, representing the highest level of criticality. This may change over the years as technology and cubesat development experiences evolve. Even more importantly than for larger spacecraft development, this document should be used as a guidance tool as part of a holistic, systems-centric engineering approach for developing cubesat missions, and no one element should be considered sacred to the process. This document follows the logic of GPR 8705.4, drawing in some of the verbiage directly, but foremost is driven by the common constraints in cubesat development.