TABLE 7.1 Risk-related Terms




An evaluation reflecting the combined answers to the questions (1) What can go wrong? (2) How likely is it? and (3) What are the consequences?

Risk assessment

The science of investigating the level of risk and the contributing factors associated with the risk of an event, process, or activity.

Risk management

The process of making decisions and taking actions to control risk based on a systematic process of risk assessment.

Risk benefit analysis

The evaluation of the risks and benefits of an activity, system, or program based on economic and performance considerations.

Programmatic risk

The potential for risk of an undesired impact on the cost, schedule, and success of a program, project, or activity.

Mission risk

The possibility of not meeting the objectives of a particular mission.

Health and safety risk

The potential for negative human health or safety consequences as a result of a particular event, process, or activity.

Risk communication

An interactive process of exchange of information and opinions regarding risk, among individuals, groups, and institutions, often involving multiple messages about the nature of risk and the expression of concerns, opinions, or reactions to risk messages.

De minimis risk

A level of risk considered below regulatory concern from the legal maxim “de minimis non curat lex” or “the law is not concerned with trifles.”

Risk perception

Sense of a hazard held by different groups of people and frequently dependent on factors other than the hazard itself, such as unfamiliarity, acuteness, and sensitization by catastrophic images.

Risk characterization

A synthesis and summary of information about a hazard that addresses the needs and interests of decision makers and of interested and affected parties.

required by NASA’s procedures for probabilistic risk assessment.1 Unfortunately, primarily because NASA has only recently required full-scope risk assessments, the risk assessment of primary interest to the committee is currently in the process of being developed and therefore was unavailable to the committee. Furthermore, the risk assessment procedures for NASA programs and projects do not require risk assessments for non-human-related missions. As a result of not having a risk assessment for either the shuttle or the robotic HST servicing missions for its review and analysis, the committee performed its own qualitative assessment of the risks of the two HST servicing options based on briefings, meetings with NASA and contractor personnel, and selected references.


NASA, 2004, “Probabilistic Risk Assessment (PRA) Procedures for NASA Programs and Projects,” NASA Procedural Requirements: 8705.5, NASA Office of Safety and Mission Assurance, Washington, D.C.

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