The work presented in this paper is based on a synergistic approach [1] integrating models of operators' tasks (described using the HAMSTERS notation) with models of the interactive system (described using the ICO notation) they are using. This synergistic approach makes it possible to bring together two usually independent (but complementary) representations of the same world. Even though supported by modeling and simulation tools, previous work in this area was rather theoretic focusing on concepts and principles in order to articulate this synergistic use of the models. The current article extends this line of research to address groupware applications. These extensions are performed on HAMSTERS notation in order to describe activities involving multiple users dealing with information flow, knowledge they are required to master and communication protocol (synchronous or asynchronous). Other extensions are performed on PetShop tool (supporting the ICO notation) in order to model and execute local and distant groupware applications. These extensions have been brought together by a more complex synergistic module bringing the two views together. Lastly, these extensions have been used for the modelling, design, and construction of a groupware system dedicated to collision avoidance of spacecraft with space debris. This case study is used to assess the applicability of the contributions and to identify paths for future work.