ABSTRACT The iBOSS project [1] (Intelligent Building Blocks for On-Orbit Satellite Servicing and Assembly) centers around two key elements: modules consisting of both, structural and functional elements, and a standardized 4-in-1 interface for docking, power, data and thermal interconnection. In this approach, the classical spacecraft subsystems are converted into specialized and standardized building blocks. These building blocks are then used to form a maintainable modular and reconfigurable spacecraft. In order to handle the technical complexity and bridge the gap between technical and economical requirements and impact, all building blocks and all derived satellites are first modeled and analyzed in a comprehensive “Virtual Testbed iBOSS” (VTi). The VTi combines virtual reality and 3D simulation techniques, and covers all relevant aspects of on-orbit assembly and operation. In this paper, we focus on the VTi and its overall concept as well as the various aspects covered by the VTi. This incorporates rigid body dynamics, control algorithms for satellites, robotic servicing in different orbits, the simulation of thermal and energy aspects as well as the simulation of the building blocks interfaces. Several reference scenarios, like satellite and servicing simulation or hardware-in-the-loop (HiL) simulation that combine virtual satellites with physical building blocks, will illustrate the feasibility of the VTi approach and its benefits for the iBOSS ecosystem. 1 INTRODUCTION The classic satellite design approach focuses on unique solutions which results in single-use-systems. This leads to high costs for development and possibly space debris after the satellites lifetime. In contrast to this, the iBOSS approach replaces the classical satellite design with a standardized and modular system concept. Typical classical satellite spacecraft subsystems are broken down into a set of standardized building blocks. These building blocks form a construction kit that allows to build up a maintainable, modular and reconfigurable spacecraft with the functionalities of a non-modular one. This type of spacecraft thereby achieves sustainability, maintainability, upgradeability, cost efficiency and allows for rapid development. In order to handle the technical complexity and bridge the gap between technical and economical requirements and impact, the iBOSS concept follows a model-based system engineering approach. Before production, all building blocks and all derived satellites are first modeled and analyzed in a comprehensive “Virtual Testbed iBOSS” (VTi) which combines virtual reality and 3D simulation techniques and covers all relevant aspects of on-orbit assembly and operation. The VTi supports engineers developing new components and satellites, helps customers designing new satellites, and gives system integrators the chance to test the entire satellite. In addition to this, it eases the communication with decision makers in government and industry organizations by incorporating technical and economic aspects. For all these tasks, the VTi offers a comprehensive model driven approach with standardized interfaces for software tools. This allows for an integration of tools and models, and results in a holistic consideration of the system under development in the application scenario (Figure 1). Figure 1: Holistic consideration of target system and application scenario. Following the iBOSS and the VTi approach, the future life cycle of a communication satellite based on the iBOSS design may look like this: based upon the requirements of the customer, a modular satellite is generated using a Computer Aided Satellite Design (CASD) tool [2]. Before going into production, this satellite model has to pass a virtual system test that is completely carried out inside the VTi. The entire VIRTUAL TESTBED FOR DEVELOPMENT, TEST AND VALIDATION OF MODULAR SATELLITES Malte Rast 1 , Andre Kupetz 2 , Michael Schluse 1 , Oliver Stern 2 , Juergen Rossmann 1 1 MMI RWTH Aachen, Ahornstr. 55, D-52074 Aachen, Germany, E-mail:{rast, schluse, rossmann}@mmi.rwth-aachen.de 2 RIF e.V., Joseph-von-Fraunhoferstr. 20, D-44227 Dortmund, Germany, E-mail: {andre.kupetz, oliver.stern}@rt.rif-ev.de