"The primary objective of the NASA safety variance policy is to define the roles of Headquarters, Centers, program managers, and safety personnel in such a way that Headquarters will maintain control over the requirements it sets while providing the Centers and program managers with the responsibility and freedom to accept risks necessary to accomplish their tasks. This is consistent with an ISO 9001 requirement of maintaining process control of services that an organization provides. It is NASA's preference to comply with requirements through an abatement process. Where this is impossible for whatever reason, then a variance may be considered."

1. Section 10.2 of Defense Systems Management College Systems Engineering Fundamentals text.