The development of Digital Twin (DT) technology in Battery Management Systems (BMSs) presents a transformative approach for maintenance, monitoring, and predictive diagnostics, especially in the demanding field of space applications. DTs, through their three-layer structure, provide an accurate and dynamic virtual representation of the physical entity, continuously updated via bidirectional data exchange provided by the communication link. Given the promising capabilities of the DT approach in real-time applications, its integration into BMSs is straightforward, as it can enhance monitoring and prediction of nonlinear electrochemical systems, such as space-grade lithium-ion batteries, supporting the mitigation of ageing effects under the unique constraints of the space environment. Despite notable progress in BMS technologies, the choice of estimation techniques consistent with the DT paradigm remains insufficiently defined. This survey examines the state of the art with the aim of bridging the conceptual framework of DTs and existing battery management algorithms, identifying the methodologies most suitable in accordance with DT architectures and principles. The scope of this paper is to provide researchers and engineers with a comprehensive overview of the advancements, key enabling technologies, and implementation strategies for Digital Twins in space BMSs, ultimately contributing to more reliable and efficient space missions.

This paper goes over the shared bus approach that is used by the team of the S5Lab (Sapienza Space Systems and Space Surveillance Laboratory) of Sapienza University of Rome. The team has launched three nanosatellites in orbit which share most of the bus, with the intent of easing development and maximizing the educational return of the missions, from conception to operations. Using the same bus and infrastructure allows to focus more time on the development and testing of the payload and reduces operational hurdles through the experience acquired from previous flights. Currently, the LEDSAT and WildTrackCube-SIMBA satellites are in orbit, with the bus based on what was learnt from the 1KUNS-PF mission, and the team is preparing to launch the GreenCube 3U CubeSat.