The main objective of this study 'DETUMBLING – Investigation of Active Detumbling Solutions for Debris Removal' was to propose and investigate a contact-based de-tumbling strategy using a robotic arm. Realistic models were developed for the chaser with robotic-arm, target and composite systems. Specific GNC strategies were developed for the different phases of the mission: robotic-arm deployment synchronisation with the target de-tumbling the composite. Two different H∞controllers were designed for the synchronisation phase, with 6-DOF and 10-DOF, respectively, and a dedicated controller was designed for the composite system. μ-analysis was used to assess the robust performance and stability of the controllers. The impact at system level, in particular the forces and torques induced at the robotic arm's joints were evaluated in simulation using a realistic model of the Envisat satellite as the mission target. Monte Carlo campaigns were run in order to assess the time domain robustness of the proposed algorithms.

The core activities were to:

• Propose a classification of space debris based on de-tumbling rates, mass, inertia, and size
• Perform a survey of possible de-tumbling strategies for each of the identified classes
• Perform a trade-off analysis of the de-tumbling strategies for each class (including chaser/target interface requirements), assessing the impact at chaser level
• Develop a realistic model for a composite system that includes a chaser, robotic-arm, and target (Envisat)
• Propose a guidance algorithm for the different phases of the mission
• Design and demonstrate the performance of a modern robust controller for the different phases of the mission
• Assess and establish the boundaries of applicability of the GNC system
• Design controllers for coupled as well as combined control
• Formulate recommendations for future space vehicle system design
• Provide inputs for an associated technology development roadmap