On-board software maintenance for manned spacecraft

Embedded software functionality and complexity have increased in such a way that the software has become a critical component in manned spacecraft. The long duration of the mission, the characteristics of the mission to an unknown environment, calling for maximum operational flexibility and reducing the duration and cost in on-board software development, have made it vitally important for manned spacecraft to have the ability to upgrade code after launch. This paper presents the requirements for software maintenance, and proposes some design details including the software architecture, the maintenance levels, the maintenance modes and some implementation methods.