Availability measures of human-equipment standby redundant data-flow system with application to NASA deep space station

This paper presents a mathematical model to evaluate availability and proportion degraded-performance of a two-unit standby data-flow system with three possible states of each unit; namely, normally operating, degraded, and failed. In addition to the operator involvement in system operation; the impact of the performance of a link-controller, as a second human component, is also incorporated into the model. The link-controller performance of the reconfiguration/link task allows for the assumption of noninstantaneous restoration of system operation. The system performance is analyzed stochastically using the theory of Markov Process. Steady-state availability and proportion degraded-performance measures have been derived and applied to an existing data-processing system. Selective graphs have also been developed to demonstrate the practical utility of the model.