This paper describes an approach for a SysML-based methodology, recently defined and applied at the European Space Agency (ESA).In 2009 a SysML-based methodology based on the European Cooperation for Space Standardization (ECSS) and International Organization for Standardization (ISO) standards was developed in the frame of the European Space Agency (ESA)/European Space Research and Technology Centre (ESTEC) study “System and Software Functional Requirements Techniques” (SSFRT).The SSFRT study investigated the feasibility of the application of model-based system engineering in spacecraft design to support the space system and software development processes, from mission level requirements to software implementation. The use of models to support the system requirements engineering process was aimed at improving the system requirements allocation process toward the software requirements engineering process. On the other side, design constraints and system requirements refinement imposed by software on the system functions realization can easily be taken into account if both processes are managed and supported by modeling techniques. The study has resulted in the definition of the Model-Based methodology to support the Space System Engineering (MBSSE) and system and software co-engineering. The study was conducted by Intecs as a prime, Thales Alenia Space and the University of Rome.In 2010, a study was conducted at ESTEC, Noordwijk to adapt and analyze the applicability of the MBSSE methodology in the Concurrent Design Facility (CDF) in the context of the Atmospheric Sample Return (ASR) mission of the Mars Robotic Exploration Preparation (MREP) program of the ESA. The CDF provides ESA an environment to apply concurrent engineering methods to spacecraft designs. During the study, the physical architecture and the functional design were in order to trace design decisions. This paper presents the model-based methodology and discusses its use in a concurrent design process. Characteristics of concurrent design, such as several mission scenarios and several satellite configurations, are discussed as well.Due to the multi-domain nature of a satellite, a variety of models are generated during the design process. A model-based approach can support the design process by combining the information of each domain into one consistent model. This model represents the actual design and supplements the document-based design to optimize the design process.