Mission assurance is a method to guarantee mission success against a known set of risks; mission assurance is generally represented as a probability against a threshold of acceptable performance. Human assurance can be considered as the likelihood of acceptable operator performance given a set of conditions that include the operator, the system, and the environment. Standard mission assurance models tend to assume a qualified crew, but do not include other aspects of the internal or external environment that may impact the reliability of the human operator. A human assurance model can be created that allows the exploration of the variability in operator performance due to the likelihood of different risks. An example human assurance model has been created for the detection of adverse trending satellite data and the need to modify the existing mission schedule to address the satellite emergency. The model leverages the Human Viewpoint framework to capture the human-focused data within the mission context. From this data, sources of risk can be identified for the socio-technical system and a risk framework developed. The resulting risk model allows exploration of the characteristics of both the operator and the operating environment, as well as the impact of organizational mitigations, on the likelihood that the socio-technical system will meet mission assurance thresholds. The method provided can be used to identify the limitations of human system performance against the established criteria.