This paper describes the mechanisms employed to control the design, coding, test, integration and updating of a large software system. In this case, the software was built to control and receive data from the hugely successful Infra-Red Astronomical satellite project (IRAS). The total software package exceeded ¼ million lines of executable code and took 100 man-years to build. Both the software and the control mechanisms employed functioned extremely efficiently, and may provide food for thought when considering the control of future space projects.