The olympus attitude and orbital control system: A case study in hard real-time system design and implementation

Abstract

This paper describes the details of, and the experiences gained from, a case study undertaken by the authors on the design and reimplementation 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 compiler 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.