Current trends in the aerospace industry for the digitization of data, tools, and services call for novel solutions that can keep track of the latest technological advancements. Moreover, the increasing drive toward model-based approaches imposes the use of models for the development of complex systems, such as satellites. New types of methods and tools are needed in order to manage the still-growing complexity of embedded systems and their corresponding models. This paper addresses issues related to space systems (in-service) operations and proposes a multimodel approach to address them. The multimodel approach aims at facilitating the task of operational diagnosis by creating a monitoring and diagnosis-dedicated system model derived from existing system design (architecture, functional behavior, and safety) models. The purpose of the diagnosis-dedicated model is to enable the codesign of the system and its diagnosis tools in order to improve the performance of diagnosis activities and the system’s availability. This paper demonstrates the interests of the suggested approach with regard to the limitations of current practices.