Payload Specialist
A Payload Specialist (PS) may or may not be a career NASA astronaut. For some missions, Mission Specialists are chosen to fulfill this role; on other missions, where very specialized scientific or medical skills may be needed, Payload Specialists are chosen by the scientists performing experiments on that mission via a special NASA selection process. The Payload Specialists have primary responsibility for performing the on board experiments. Specifically, the Payload Specialist duties are: calibrating experiment equipment, evaluating experiment data quality, and communicating effectively via voice link with the investigator team on the ground. The Payload Specialist (PS) understands the design and operation of the payload and makes on board decisions about detailed experiment operations. These decisions are usually based on consultation with the investigator team.