ABSTRACT
A low earth orbiting spacecraft bus, for example, is often partitioned into the following subsystems: structures and mechanisms, thermal control, electrical power, attitude determination and control, propulsion, communications, and command and data handling. Systems comprise various subsystems which also comprise several subsubsystems and so on. It is intuitively apparent that complexity grows as more subsystems and tiers are added to the system. A central concern of any program manager is how to determine the true status of the development. A central motivation for conducting a technical review is to gain consensus with all stakeholders that the requirements and design, at the level of the review, are of sufficiently low risk or acceptable risk, so as to continue toward the next milestone. There are relatively few complex system development efforts that are accomplished on schedule and within the proposed cost.
