Cost effective satellite development with use of an Ada microprocessor

This paper describes the development of an embedded computer system, where Ada is used. The system will be used in a scientific satellite and handle the onboard attitude control functions in space. The onboard computer activities for this project started early 1994; integration of the onboard computer hardware and software occurs during 1995, and the satellite will be launched in 1997. Saab Ericsson Space develops the embedded computer system, hardware as well as software, on a contract from the Swedish Space Corporation. Low cost of the embedded computer system is a very important requirement. Therefore risk areas for the cost had to be identified and handled in a proper manner. The following requirement areas were found to be critical from the cost point of view:. Some attitude sensors and/or actuators are not defined until very late in the project, resulting in a number of software modifications to be done late in the project.. Available board area for the onboard computer system is relatively small, a single 130*212 nun board for two redundant computers.. Hard Real Time requirements exist for the sofhvare: interrupts may occur each 88 pss; interrupt processing must be done within these 88 ps; interrupts cannot be missed.. High Order Language is required.. High processing power is needed to handle attitude control calculations. A 32-hit microprocessor system developed by Saab Ericsson Space was found suitable for the requirements of this project and was selected to be used in the onboard computer. This microprocessor system is developed for use in real time embedded aerospace applications, where resources often are limited, and the environment requires use of radiation tolerant hardware. Saab Ericsson Space has developed processors for aerospace applications since 1972. Examples of such applications are the Ariane launcher and the SPOT satellite programs. It was decided to use Ada as programming language in order to meet the requirement of late changes in the definition of sensors/actuators-the capability of Ada to support sohware maintenance helps to handle this requirement properly. The selected microprocessor supports compact hardware designs because many functions needed in embedded computer applications, are implemented on the microprocessor chip. The six of memory is small because Permission to copy without fee all or part of this material is granted provided that the copies are rwt made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear. and notice …