Development of a Digital Twin for Spacecraft Proximity Operations

Autonomous rendezvous and capture are key capabilities for future on-orbit servicing (OOS) missions. Two main strategies are typically employed: berthing, where a robotic manipulator seizes the target, and docking, often implemented through probe-and-drogue mechanisms. While both approaches are well established in spaceflight operations, their detailed modeling and systematic comparison remain open research challenges. This paper introduces a dedicated multibody framework developed within the MUSAPOEM project to analyze and contrast berthing and docking operations. The berthing model comprises a servicer spacecraft, a non-cooperative target, and a 7-DOF robotic manipulator equipped with a gripper-type end effector. In the proposed approach, detailed CAD-based geometries are decomposed into convex subcomponents, enabling the accurate simulation of probe insertion, compliant latching, and nonlinear contact force exchanges within Simscape Multibody. A comparative analysis highlights the complementary nature of the two approaches. Berthing offers adaptability and robustness when dealing with unprepared or uncooperative targets, whereas docking provides a compact, autonomous solution optimized for cooperative missions with standardized interfaces. Although the docking results are currently limited to model development, the framework establishes a solid basis for extending the analysis to hard docking and for integrating control strategies. In this way, the work contributes to advancing high-fidelity simulation tools that support the design and validation of next-generation OOS missions.