Active antenna failure modeling and architecture modifications

In the space industry, reliability refers to a satellite's ability to perform a function, typically its mission, over a given time interval. Reliability is specific to dependability, and particularly so for satellites which are non-repairable systems, such as communications satellites, for which there are no second chances.

Experience shows that mission losses are always more costly than investment in quality assurance and reliability, especially in the case of very expensive communications satellites.

During the design phase of a project, reliability engineers must assess the reliability of the various architectures under consideration, and contribute their point of view to discussions between the various parties with a view to reaching a compromise. Indeed, reliability is an important criterion considered by engineering and can discriminate one design from another.

As the systems studied become increasingly complex, Thales Alenia Space, a player in the satellite industry, is adapting its tools and methods to meet the challenges it faces. For example, the emergence of MBSA (model-based safety assessment) is a promising technique for operational safety. It consists in representing a system by a high-level model in order to study the propagation of failures, and then to estimate its reliability by means of computer simulations. Its notable advantage lies in its flexibility, which allows rapid architectural changes, putting the dependability engineer back at the heart of architectural discussions.

In this article, we focus on the flexibility of MBSA tools, i.e. their ability to rapidly model several similar architectures. This flexibility is compared in particular to Petri net modeling, the origin of the concepts developed by MBSA.