ROBOTIC CABLE-BASED DE-TUMBLING OF SPACE DEBRIS
The threat posed by orbital debris has grown in recent years. Any collision with space debris may add up to thousands of additional debris that increase collision probability. Recent launches of new satellite constellations to Low Earth Orbit (LEO) has further cluttered LEO and increases the chance of collision with debris.
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The most dangerous debris in orbit consists of large bodies, such as spent rocket stages. To successfully reduce the risk of collisions, and to clean up the space environment, large bodies need to be removed through the use of active debris removal (ADR) missions. One promising technology for ADR are space tethers, which can include tethered robotic manipulators, nets, and harpoons.
CURRENT RESEARCH
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Online Estimation and Control for Towed Debris Systems:
The objective of this research is to develop the necessary knowledge for autonomous cable-based de-tumbling of space debris.
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To de-tumble non-cooperative debris, controls need to be applied to the chaser to maintain a safe relative distance from the debris and to de-tumble the debris. Currently:
- A sliding mode controller (SMC) is employed for chaser attitude stabilization.
- To maintain a relative distance between the chaser and target debris, a feedback proportional-integral-derivative (PID) thrust controller is applied.
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The debris inertial parameters must be known in order to both properly and optimally control the debris motion after capture. However, as the debris is non-responsive, these parameters are often unknown. In this work:
- An extended Kalman filter (EKF), and an unscented Kalman filter (UKF) are applied to estimate the debris orientation, rotation vector, and principal mass moment of inertia parameters.
- It is assumed that the chaser attitude and velocity states, and the debris relative position and velocity states are known to the estimator.
- Combinations of sensors are utilized for measurement generation at both synchronous and non-synchronous update rates, such as a tension sensor, camera sensor, and gyroscopes.
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Parameter Identification for Net-Wrapped Towed Debris Systems:
The objective of this research is to develop an efficient modeling and parameter-identification framework for tethered satellite systems to emulate the towing dynamics of debris captured by a net in Active Debris Removal (ADR) missions. The goal is to approximate the dynamics of computationally expensive high-fidelity net simulations using a lower-order dynamic model.​
-A simplified tethered satellite system (TSS) model is developed to approximate the dynamics of a net-wrapped debris system while significantly reducing computational complexity.
-The model represents the chaser spacecraft, debris, and tether connection using a reduced set of masses and tethers to emulate the key dynamical behavior of a high-fidelity net simulation.
-An optimization-based parameter identification framework is formulated to determine equivalent system parameters such as tether stiffness, damping, and lumped masses.​​
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KEY FINDINGS
Online Estimation and Control for Towed Debris Systems:
The application of Kalman filters to this estimation problem revealed that:
- A known non-zero tension in the tether is required to estimate the principal mass moments of inertia of the debris.
- The UKF performs significantly better than the EKF for this estimation problem, and should be applied instead of an EKF.
- Best estimation results are obtained from low amplitude, high-frequency tension oscillation profiles in the tether.
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Through application of control algorithms to the tethered space debris system, we have found that:
- A PID controller is sufficient for maintaining a desired relative distance between the chaser spacecraft and debris.
- Tension in the tether is maintained and is capable of counteracting the rotation of debris in some cases.​
- Control performance is maintained when using estimated states.
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Parameter Identification for Net-Wrapped Towed Debris Systems:
-The proposed optimization-based framework successfully identified the parameters of the lower-order tethered satellite system (TSS), enabling it to approximate the dynamics of the high-fidelity net-based debris-towing model.
-The identified reduced-order model reproduced the key translational dynamics of the high-fidelity system while requiring dramatically lower computational effort (minutes vs. several hours).
-Benchmark validation demonstrated that the optimization framework converges to parameters close to the true values, confirming the robustness of the parameter identification approach.
Online estimation and control pseudo-code
FUTURE RESEARCH
Online Estimation and Control for Towed Debris Systems:
- Apply more robust control to dissipate the residual angular momentum of the debris.
- Release numerous assumptions in the current work.
- Investigate the performance of other estimation methods.
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Parameter Identification for Net-Wrapped Towed Debris Systems:
-Expand the parameter identification datasets to include additional mission conditions such as varying initial chaser–debris distances, thrust profiles, and debris rotational states.
-Investigate a wider range of debris orientations and rotation axes to further improve the fidelity and generalizability of the reduced-order model.
PUBLICATIONS
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L. Field, D. Bourabah, E. M. Botta. Online Control and Moment of Inertia Estimation of Tethered Debris. 2024 AIAA SciTech Forum, Orlando, FL, January 2024. DOI: 10.2514/6.2024-1286
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D. Bourabah, C. Gnam, E. M. Botta. Inertia Tensor Estimation of Tethered Debris through Tether Tracking. Acta Astronautica. Vol. 212 (2023), pp. 643-653. DOI: 10.1016/j.actaastro.2023.08.021
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D. Bourabah, L. Field, E. M. Botta. Estimation of Uncooperative Space Debris Inertial Parameters after Tether Capture. Acta Astronautica. Vol. 202 (2023), pp. 909-926. DOI: 10.1016/j.actaastro.2022.07.041​
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Field, L., Bourabah, D., & Botta, E. M. (2025). Online Estimation and Control of Tethered Debris Using Tension and Feature Tracking. Journal of Guidance, Control, and Dynamics, 48(2), 443-449. doi.org/10.2514/1.G008295
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Boonrath, A., Singh, T., & Botta, E. M. (2024). Identification of parameters for tethered satellite system to emulate net-captured debris towing. Acta Astronautica, 225, 676-688. doi.org/10.1016/j.actaastro.2024.09.022