Incorporating modern development and evaluation techniques into the creation of large-scale, spacecraft control software

Abstract

One of the major challenges facing the development of today's safety- and mission-critical space systems involves the construction of software to support the goals and objectives of these missions, especially those associated with NASA's Space Exploration Initiative, which has now become the focus of the US Space Program and its contractors. Consequently, the software used to implement much of the functionality in the various flight vehicles and ground facilities must be given special consideration. This dissertation outlines a new approach to spacecraft software development that focuses on incorporating modem software engineering techniques into the spacecraft domain including (1) a product-line approach to the software development enterprise and (2) a software architecture-centric design process to support that approach. The new product-line approach is demonstrated through its application to the Exploration Initiative. The technical and managerial aspects of the product line, which are required to successfully field the line, are described in detail. Among the technical artifacts developed to support the line, the software architecture is the most important.

(cont.) Consequently, it was necessary to create a systems engineering-based development, evaluation, and selection process for the construction of the software product-line architecture. This development approach is known as Multi-Attribute Software Architecture Trade Analysis (MASATA) and is demonstrated on the vehicles and facilities of the Exploration Initiative, the Crew Exploration Vehicle in particular. Based on the functional requirements of the Exploration Initiative and the quality attributes desired by the stakeholders, a software product line architecture is presented. The desired quality attributes include analyzability with respect to safety, ease of verification and validation, sustainability, affordability, buildability, ability to meet real-time requirements and constraints, and "monitor"-ability. Several architectural style options were selected for evaluation with respect to the requirements and attributes through MASATA including traditional subsystem-based decomposition, state analysis, functional decomposition and implicit invocation. The conceptual software product-line architecture selected to support the Exploration Initiative is based upon these results.