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Spacecraft formation flying and satellite cluster flight have seen growing interest in the last decade. However, the problem of finding the optimal debris collision avoidance maneuver for a satellite in a cluster has received little attention. This paper develops a method for choosing the timing for conducting minimum-fuel avoidance maneuvers witho...
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... second example is a cluster generated using the FreeFlyer space mission design, analysis, and operations software. First, a piece of debris and a satellite are generated (see Table 3). Then, the satellite is duplicated by shifting its mean anomaly to generate cluster members that are 50 km apart. ...
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Citations
... The optimal maneuver must balance multiple factors such as collision probability, propellant consumption, mission objective, and radio visibility zones [89]. Moreover, the optimal decisions may need to take into account several debris simultaneously when planning maneuvers [90], increasing the problem's complexity. Addressing these issues requires adequate decision-support models capable of evaluating the trade-off between these different objectives and operational constraints, and efficiently finding the optimal solutions. ...
... Developing autonomous collision avoidance systems is a challenging task. The optimal maneuver must take into account a multitude of considerations including the likelihood of a collision, expenditure of propellant, mission objectives, and radio visibility zones [89], [90]. We discuss a few AI-based optimization and learning algorithms for achieving autonomous collision avoidance planning and execution. ...
This chapter explores the role of data management, risk assessment, and decision-support algorithms for spacecraft collision avoidance. It discusses the important role of space monitoring and detection technologies in gathering data crucial to adequate space traffic management and risk mitigation. The chapter explores various data collection methods, processing techniques, and data integration within advanced collision avoidance decision-planning frameworks. We discuss the challenges of handling data from diverse space monitoring technologies and provide an overview of methods developed for data integration and fusion. In addition, the chapter gives an overview of models and algorithms for assessing collision risks, maneuver planning, and execution. Particularly, it discusses emerging trends, including artificial intelligence and data-driven decision-making, that enhance situational awareness and proactive collision avoidance strategies. Overall, this work seeks to provide an outline of the different technological aspects involved in successful collision avoidance implementation, from data management to risk assessment and decision planning, in order to ensure the safety and sustainability of space operations.
... Abay (Abay, 2017) employed the same approach to obtain an optimal impulsive CAM based on the SGP4 propagator. The problem of computing the minimum-fuel CAM design for a satellite in a cluster without violating the intersatellite maximal distance was investigated by Denenberg and Gurfil (Denenberg & Gurfil, 2017). ...
The objective of this paper is to provide a stochastic framework to optimally avoid collision between a maneuverable spacecraft and a space object or debris. The satellite collision can be caused through a cyber-attack on a satellite by colliding it with a considered strategic satellite. Consequently, it is highly imperative that critical operational space assets be provided with autonomous collision avoidance systems. The collision avoidance methodology proposed in this paper will reduce the collision probability to an acceptable level and protect the satellite against indirect kinetic cyber-attacks initiated by designing optimal collision avoidance maneuvers using a stochastic model predictive control strategy. The collision probability is estimated using the available historical Two-Line Elements of determined objects, and the model predictive control scheme guarantees the safety of the space close approaches. The proposed and developed collision-avoidance countermeasure methodology is numerically simulated for the collision case study between the Iridium-33 and the Cosmos-2251 satellites. The results demonstrate and illustrate the effectiveness, capabilities, and advantages of our proposed methodology in avoiding probable collisions due to indirect kinetic cyber-attacks.
... The problem of optimum single-maneuver and single-conjunction collision avoidance between spherical objects in low Earth orbit (LEO) using an impulsive ΔV was addressed by the work of Bombardelli and Hernando-Ayuso in 2015 [1]. Other aspects of impulsive CAM, including the addition of formation-keeping constraints [2], the inclusion of velocity uncertainties [3], and a possible laser-based implementation, have also been investigated [4]. ...
The problem of optimum low-thrust collision avoidance between two objects in circular orbits is investigated. The thrust vector of the maneuvered satellite, applied continuously for a given time span, is held constant in magnitude as a consequence of Pontryagin's maximum principle while its orientation is controlled following the solution of an optimal control problem using the indirect method written in B-plane coordinates. In addition, a simple, fully analytical solution for a tangential maneuver is derived and compared with the controlled solution. Results show that the analytical solution is sufficiently accurate and adequate for a preliminary design of the maneuver. The influence of environmental perturbations is also addressed and shown to be negligible.
... Denenberg and Gurfil [19] developed a collision avoidance maneuver evaluation technique for a satellite cluster flight. Pastel [20] estimated the collision probabilities between satellite and debris by using the Adaptive Splitting Technique. ...
In recent years, the number of space debris has increased significantly, which can threaten the safety of operational satellites. In this paper we developed an accurate model for active satellite protection from collision in order to determine close approaches between two objects (satellites and /or debris) using the Hoot's method and the time of close approach. We calculate the minimum relative distance considering J2 and atmospheric drag perturbations, and compared it to the close approach distance. The Collision probability between two closed objects is calculated using Chan model and analyzed in a given timescale to avoid any dangerous collision. We applied our models on the cataloged debris (more than 1000) resulted from the crash between Iridium 33 and Cosmos 2251; in addition, ten satellites from the Iridium satellites list at the same altitudes of the debris crowdie region are considered. The numerical results have shown one real case of close approach with high probability of collision that may threaten one of those active satellites.
... In the face of the increasing number of space objects, it might be necessary to take account several debris pieces when planning maneuvers. 6,7 There are several systems for CAM calculation such as CORAM (Reference 8) and OCCAM (Reference 9). ...
The number of space objects will grow several times in a few years due to the planned launches of constellations of thousands microsatellites. It leads to a significant increase in the threat of satellite collisions. Spacecraft must undertake collision avoidance maneuvers to mitigate the risk. According to publicly available information, conjunction events are now manually handled by operators on the Earth. The manual maneuver planning requires qualified personnel and will be impractical for constellations of thousands satellites. In this paper we propose a new modular autonomous collision avoidance system called "Space Navigator". It is based on a novel maneuver optimization approach that combines domain knowledge with Reinforcement Learning methods.
The problem of passive safety between spacecraft is studied in this paper by means of backward reachable sets and orbital element differences. These reachable sets characterize the initial states that enter a swept region around a designated spacecraft within some time horizon, leading to collision or conjunction events. We provide an in-depth passive safety analysis using such representations and discuss how the motion of spacecraft can be constrained to satisfy such safety constraints. The work herein is particularly relevant for future formation-flying missions but can be extended to certain constellations, for example, Walker constellations. We demonstrate how to compute these sets for general dynamics models, which typically require numerical methods, but provide analytical and closed-form solutions for the Keplerian case as well as when first-order secular [Formula: see text] perturbations are considered with a mean orbital element difference description. Additionally, we show how the passive safety constraint based on such sets can be further simplified (or reduced) by considering projections or slices of the derived reachable sets. Finally, we propose an algorithm that finds passively safe configurations when considering multiple spacecraft. Simulations verify the passive safety constraints derived in this paper and their utility for a number of design cases in formation flying and a [Formula: see text]-perturbed low-Earth-orbit Walker constellation. In the latter case, long-term passive safety is shown even when subjected to unmodeled perturbations.
We develop a spacecraft rendezvous policy that ensures safe, collision-free trajectories under various thrust failure scenarios. We use backward reachable sets (RSs) to characterize the unsafe region where, if a failure occurs, a collision between a chaser and a target spacecraft cannot be avoided with the remaining available thrust. The chaser spacecraft is guided toward the target via model predictive control (MPC) that ensures abort safety by avoiding the unsafe region, which is locally convexified with half-spaces. Simulations of the rendezvous policy on various orbits demonstrate that the approach ensures safe aborts in the event of multiple thruster failures, passive abort safety under total thruster failure, and achieves some robustness to unmodeled orbital perturbations.
Removing space debris is an urgent task to ensure sustainable space activity. Towards this end, we propose herein a tethered plate satellite that can remove many items of small space debris successively by collisions alone without capturing them or performing major orbital manoeuvres. The strategy involves a tethered plate that moves more slowly than the space debris at the same altitude so that the speed difference in the collision causes re-entry of the space debris. Numerical verification using an on-orbit object database indicates that, for the requisite number of collisions, this strategy would require a reasonable amount of orbital manoeuvres. The results indicate that six such spacecraft operating for one decade would suffice to reduce the amount of removable space debris in a certain altitude range by 96.10%. Based on these results, a mission concept is proposed in which debris-removal systems would remove almost all the removable space debris in a given altitude range, thereby allowing for the operation of large satellite constellations.
The recent decades have witnessed a tremendous growth in the number of satellites and debris in space, leading to an increasingly high risk of collision between space objects. Collision warning aims at assessing the collision risk between space objects and attempts to identify possible collisions in order for satellites to perform evasive maneuvers in advance. Current collision warning methods are based on the computation of collision probability and comparison with some tolerance threshold. Such a threshold is usually set according to experience. In contrast, this paper proposes to use covariance ellipsoid with a user defined Mahalanobis distance to represent the most possible region in which the relative position vector distributes. Zero vector represents the collision event, and once it enters this ellipsoid, a collision warning occurs. A collision warning function along with a definite threshold is then formulated based on this criterion. Moreover, in order to rapidly predict the possible collision intervals, a self-adaptive Hermite interpolation technique is applied to approximate the collision warning function by piecewise cubic polynomials for efficient roots finding. Finally, the proposed collision warning criterion has been evaluated in several collision scenarios. Comparison experiments are also conducted with the brute force method and analytical propagators. The simulation shows that the calculation of collision warning interval based on the proposed criterion is effective, and the self-adaptive Hermite interpolation method performs high efficiency and accuracy.
