A Cognitive Task Analysis of Safety-Critical Launch Termination Systems

Abstract

The National Aeronautics and Space Administration (NASA) has been conducting an investigation of human interaction with critical elements of NASA’s Launch Termination System (LTS). This safety-critical system requires quick decision making on the part of highly trained users in order to maintain safe launch operations. A team of NASA evaluators has completed a detailed assessment aimed at improving the Graphical User Interface (GUI) of NASA’s Range Data Display System (RDDS), a key component of the LTS. The RDDS forms the vital man-machine link which ingests high volumes of system data in real-time and displays this data to NASA’s Range Safety personnel to enable them to assess launch vehicle trajectory and performance status. The RDDS displays the real-time state of the launch vehicle and its complex subsystems to users in order to support arm/destruct decisions (made by NASA’s Range Safety personnel) to facilitate safe launch operations. These decisions are highly time-sensitive, and users must act quickly in order to prevent serious injury or death and extensive damage to equipment or property. The NASA assessment team performed a Cognitive Task Analysis (CTA) to derive the user informational requirements needed to develop data driven, user information software requirements in support of a new RDDS software upgrade. The CTA was designed to address the unique aspects of this particular system, while focusing on the operational context within which the system is used by highly specialized personnel. This analysis and the resulting requirements form the first step in providing human factors guidance to software developers throughout the design, development, and fielding of the new RDDS software GUI. This paper will focus on the applied human factors methods and techniques employed, how these methods and techniques were used to derive user information design requirements, the lessons learned from this activity, and areas for future work. The authors intend to provide human factors practitioners with an example of how CTA methods and techniques may be adapted to meet the particular needs of a project, with special consideration given to the design of safety-critical systems.