This paper describes the details of, and the experiences gained from, a case study undertaken by the authors on the design and re-implementation of the Olympus Satellite's Attitude and Orbital Control Systems (AOCS). The goal of the study was to demonstrate that real-time systems can be implemented using Ada and its tasking facilities. The system was designed using HRT-HOOD, analysed using Deadline Monotonic Scheduling Analysis, and implemented on a M68020-based system using a modified York

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... iler and run-time support system (the modifications are compatible with those proposed for Ada 9X). Our results indicate that systems can be designed to have the flexibility given by multi-tasking solutions, and yet still obtain the same levels of guarantees as those given by cyclic executives.