Using two line elements as data source, an adaptive method using antidromic window moving for detecting maneuvers of space objects was proposed. Adaptive window configuration model was established to get detection window for different objects. Meanwhile, cross arc prediction was integrated in order to obtain the maneuver time more precisely. Applying antidromic window moving method, the maneuver in the latest epochs can be detected. The results were compared with real maneuvers as well as in the existing literature. It is shown that the proposed method can adapt to the window configuration of maneuvering detection of space objects on different orbits. Besides, the detection success rate can reach more than 90% under the given simulation conditions. Moreover, the accuracy of maneuver time estimation is observably higher than that of existed method. Simulations of the approach proposed have demonstrated good performance in near-real-time maneuver detecting.

In order to solve the problem that it is difficult to identify the forced motion intention of non-cooperative targets, an intention recognition method based on BiGRU (bi-directional gated recurrent unit) network was proposed. The non-cooperative target was categorizes into five forced motion intentions: "forced round fly-around" "forced drip-drop fly-around" "fixed-point oscillating" "line approach" and "hop approach", and the forced motion intention maneuver information dataset of the non-cooperative target was established. Based on the maneuver time series information of the non-cooperative target after entering the observation range of our spacecraft, the BiGRU network was utilized to train on the potential correlation between the time series data and the forced motion intention, so as to realize the intention recognition of the non-cooperative target. The simulation results demonstrate that the detection accuracy of the BiGRU network-based forced motion intention recognition method for non-cooperative targets achieve 98.35%. This method can improve the ability to identify the intentions of non-cooperative targets and provide a technical reference for the safety of our spacecraft in orbit.

Orbital maneuver planning is an important part of the design of complex space missions such as rendezvous and docking, lunar exploration, etc. However, the varying configuration requirements of different missions for orbit transfer positions, maneuver magnitudes, and targeting parameters pose significant challenges to the generalized modeling and solution of maneuver planning. Regarding this problem, a generalized orbital maneuver planning modeling method based on orbital segments was proposed, which abstracts the maneuver requirements of different scenarios into orbital segments, stopping conditions, and constraints, forming a building-block spacecraft mission description model. The orbital maneuver requirements were converted into a unified nonlinear programming problem, which was subsequently solved by employing three distinct methods: differential correction, sequential quadratic programming, and intelligent optimization algorithms.A software module ATK. Astromaster was developed as a core module for ATK (aerospace tool kit) software. Simulation results show that the proposed method can achieve general orbit maneuver modeling and solving in different scenarios.

Perturbed Lambert Problem forms the fundamental basis for tasks such as spacecraft rendezvousand on-orbit servicing. Due to the lack of an analytical solution for the perturbed Lambert problem, numerical solutions can only be obtained through iterative computations. Consequently, existing methods primarily focus on improving iteration convergenceand computational efficiency. Building upon current homotopic iteration methods, this paper introduces the general concept of the A* algorithm for graph searchand proposes a pruned homotopic iteration approach. Firstly, by combining the gradient direction of the state transition matrix from the terminal position error to the initial velocity increment with the target direction, an iteration direction is derived, and a homotopic mapping based on the A* algorithm is designed. Secondly, utilizing Taylor expansion, a linear perturbation matrix is devised, enabling pruning of divergent end-position paths. This addresses the issue of ineffective iterations due to initial velocity divergence that conventional methods such as Newton's shooting methodand quasi-linearization fail to exclude. Simulation results demonstrate that while ensuring the attainment of optimal solutions, our proposed method improves computational efficiency by over 25%, compared to existing homotopic methods, featuring a broader convergence range. Moreover, the method exhibits favorable characteristics regarding initial value convergence. In the case of orbit transfer in the Earth-Moon three-body system, it achieves more than a 30% increase in computational efficiency compared to quasi-linearization techniques.

The concept of the spacecraft Reachable Domain (RD) has garnered significant scholarly attention due to its crucial role in space situational awareness and on-orbit service applications. While the existing research has largely focused on single-impulse RD analysis, the challenge of Multi-Impulse RD (MIRD) remains a key area of interest. This study introduces a methodology for the precise calculation of spacecraft MIRD. The reachability constraints specific to MIRD are first formulated through coordinate transformations. Two restricted maneuvering strategies are examined. The derivation of two extremum conditions allows for determining the accessible orientation range and the nodes encompassing the MIRD. Subsequently, four nonlinear programming models are developed to address two types of MIRD by skillfully relaxing constraints using scale factors. Numerical results validate the robustness and effectiveness of the proposed approach, showing substantial agreement with Monte Carlo simulations and confirming its applicability to spacecraft on various elliptical orbits.

In the face of the increasingly complex space security situation, this paper proposes an approach based on spacecraft reachable domain for spacecraft maneuvering approach threat calculation, assessment, and avoidance. Firstly, a general method to solve the reachable domain for spacecraft with single limited-magnitude impulse based on the reachable criterion is presented. Secondly, the region in the threat domain of on-orbit spacecraft is calculated by judging the position relationship between its orbit and the reachable domain of incoming maneuvering spacecraft which is the danger area. Thirdly, a threat evaluation index is defined by means of the time two spacecraft enter and exit the danger area. The threat of on-orbit spacecraft is measured from two aspects: position matching and time window matching. Based on minimizing the danger area, an active avoidance strategy of spacecraft with optimum multi-impulses maneuver is given to avoid the danger area. The simulations show that the on-orbit spacecraft can avoid the danger area while satisfying the given constraint conditions, and return to the proper orbit with minimum fuel consumption.

The collision probability computation of space objects plays an important role in space situational awareness, particularly for conjunction assessment and collision avoidance. Early works mainly relied on Monte Carlo simulations to predict collision probabilities. Although such simulations are accurate when a large number of samples are used, these methods are perceived as computationally intensive, which limits their application in practice. To overcome this limitation, many approximation methods have been developed over the past three decades. This paper presents a comprehensive review of existing space-object collision probability computation methods. The advantages and limitations of different methods are analyzed and a systematic comparison is presented. Advice regarding how to select a suitable method for different short-term encounter scenarios is then provided. Additionally, potential future research avenues are discussed.