A novel hybrid scheme for the maneuver detection and estimation of a noncooperative space target was proposed in this study. The optical measurements, together with the range and range rate measurements from the ground-based radars, were used in the tracking scenarios. In many tracking scenarios, radar resources for non-cooperative targets are constrained, particularly for near-earth targets, where multiple objects can only be tracked by a single radar at a time. This limitation hinders the accurate estimation of noncooperative target maneuvers, and can at times result in target loss. Existing literature has addressed this issue to some extent through various maneuvering target-tracking methods. To address this problem, a hybrid maneuver detection and estimation method that combines the input detection and estimation extended kalman filter and the weighted nonlinear least squares method is presented. Simulation results demonstrate that the proposed method outperforms the previous method, offering more accurate and efficient estimations.

Small bodies in the solar system are known to be covered by a layer of loose unconsolidated soil composed of grains ranging from dusty sands to rugged boulders. Various geophysical processes have modified these regolith layers since their origin. Therefore, the landforms on regolith-blanketed surfaces hold vital clues for reconstructing the geological processes occurring on small bodies. However, the mechanical strength of small body regolith remains unclear, which is an important parameter for understanding its dynamic evolution. Furthermore, regolith mechanical properties are key factors for the design and operation of space missions that interact with small body surfaces. The granular penetrometer, which is an instrument that facilitates in situ mechanical characterization of surface/subsurface materials, has attracted significant attention. However, we still do not fully understand the penetration dynamics related to granular regolith, partially because of the experimental difficulties in measuring grain-scale responses under microgravity, particularly on the longer timescales of small body dynamics. In this study, we analyzed the slow intrusion of a locomotor into granular matter through large-scale numerical simulations based on a soft sphere discrete element model. We demonstrated that the resistance force of cohesionless regolith increases abruptly with penetration depth after contact and then transitions to a linear regime. The scale factor of the steady-state component is roughly proportional to the internal friction of the granular materials, which allows us to deduce the shear strength of planetary soils by measuring their force–depth relationships. When cohesion is included, due to the brittle behavior of cohesive materials, the resistance profile is characterized by a stationary state at a large penetration depth. The saturation resistance, which represents the failure threshold of granular materials, increases with the cohesion strength of the regolith. This positive correlation provides a reliable tool for measuring the tensile strength of granular regolith in small body touchdown missions.

With the increase of space debris, space debris removal has gradually become a major issue to address by worldwide space agencies. Multiple debris removal missions, in which multiple debris objects are removed in a single mission, are an economical approach to purify the space environment. Such missions can be considered typical time-dependent traveling salesman problems (TDTSPs). In this study, an intelligent global optimization algorithm called Timeline Club Optimization (TCO) is proposed to solve multiple debris removal missions of the TDTSP model. TCO adopts the traditional ant colony optimization (ACO) framework and replaces the pheromone matrix of the ACO with a new structure called the Timeline Club. The Timeline Club records which debris object to be removed next at a certain moment from elitist solutions and decides the probability criterion to generate debris sequences in new solutions. Two hypothetical scenarios, the Iridium-33 mission and the GTOC9 mission, are considered in this study. Simulation results show that TCO offers better performance than those of beam search, ant colony optimization, and the genetic algorithm in multiple debris removal missions of the TDTSP model.

A new era of up-close asteroid exploration has been entered in the 21st century. However, the widely rugged terrain and microgravity field of asteroids still pose significant challenges to the stable landing of spacecraft and may even directly lead to the escape of the explorer. Owing to the substantial energy dissipation arising from the interaction among multiple bodies, the flexible net, which is a typical multibody system, may be capable of overcoming the above problems. In this study, a dynamical model was established to analyze the movement of the flexible net spacecraft (FNS) near and on the asteroid comprehensively. First, we investigated the dynamical environment of the target asteroid by combining the polyhedron method and spherical harmonics parametric surface modeling approach. Thereafter, we constructed the multibody dynamics model of the explorer using the linear Kelvin-Voigt method. Subsequently, we studied the collision process between the FNS and asteroid based on the spring-damper contact dynamics model. The trajectory and speed of the FNS could be derived by solving the system dynamic equations in parallel. Finally, we analyzed the deformation, descent, jumping motion, and surface movement process of the FNS during the movement. Consequently, a promising scheme is provided for asteroid exploration missions in the future.

This paper describes a rapid method for validation and visualization of agile Earth-observation satellites scheduling. Benefited from the previous work, various algorithms are proposed for scheduling the observations of agile satellites. However, the satellite maneuvers are three-dimensional, this characteristic makes it difficult for the operation engineers to validate and interpret the scheduled solutions. They have to plot these attitude data to analyze different situations such as an observing phase or a slew maneuver. Finally, one tries to imagine the three-dimensional situations from many one-dimensional plots, which is time-consuming and susceptible to errors. Moreover, now it is low-efficiency to deal with the data about ephemeris, targets, etc., because different software platforms are required. In this research, a validation and visualization method is suggested to overcome this barrier. It is successful to integrate the Satellite Tool Kit ActiveX and the C# programming language. Based on the embedded scheme, all the interaction and assessment can be visualized. Practical techniques for modelling satellite objects, sensor objects, target objects and satellite attitudes are presented. Such a method has been applied for Chinese agile satellites project, and a software interface has been developed. The simulation results indicate that the proposed method is intuitive and efficient. Note that this method is general, and thus it can be applied to other Earth observation missions. Enough details are provided for interested readers to develop the software interface.