In X-ray pulsar-based navigation, phase and Doppler frequency estimation based on the maximum likelihood estimation and grid search methods is widely used in practical missions and theoretical analysis. However, due to the non-convexity of the objective function and the inefficiency of the grid search method, a key challenge is how to achieve fast estimation of phase and Doppler frequency while maintaining accuracy. To address this issue, the fast and high-precision estimation of phase and Doppler frequency based on prior information and non-convex optimization is proposed in this paper. First, leveraging the prior state information of the spacecraft, an enhanced on-orbit phase model is established by considering a reference time at any given moment. Then, the statistical properties of the parameters to be estimated are analyzed, and the corresponding prior probability model is constructed, using the Bayesian estimation model as the objective function. Finally, incorporating non-convex optimization theory, the Nesterov-adaptive moment estimation is employed to automatically adjust the step size of the quasi-Newton algorithm. Simulation and experimental results demonstrate that the proposed method achieves rapid convergence with high precision, effectively balancing real-time performance and estimation accuracy compared to traditional phase and Doppler frequency estimation methods. Using the Crab pulsar as the primary case study, when the observation duration is 1800 s and the detector area is 30 cm2, the proposed method reduces the running time by 99.91

The Strap-down Inertial Navigation System/Refraction Celestial Navigation System (SINS/RCNS) integrated navigation is a high-accuracy autonomous positioning method. The accuracy of this method is fundamentally limited by errors in the atmospheric refraction model. However, atmospheric models are difficult to be highly accurate due to factors such as measurement errors, numerical approximations, physical simplifications, and chaotic dynamics, and their uncertainty will always persist. To solve this problem, a general atmospheric refraction model containing four parameters is established, and a new SINS/RCNS integrated navigation method based on self-calibration of the atmospheric refraction model using starlight refraction measurements is proposed. Simulations show that the proposed method can effectively estimate the four parameters of the atmospheric refraction model, especially the terms related to the logarithmic term and constant term. They have a significant impact on refraction apparent height and navigation performance. The proposed SINS/RCNS integrated navigation method, which incorporates self-calibration of atmospheric refraction model, demonstrates relatively stable positioning performance across different atmospheric refraction models. Compared with traditional SINS/RCNS approaches lacking such self-calibration, the positioning accuracy is improved by approximately 54.44% to 87.77% under various constant atmospheric model error cases and 75.98% under the case of varying error. This study provides technical support for the engineering application of SINS/RCNS integrated navigation systems.

Near-Earth asteroid impacts represent a significant and long-term potential threat to humanity.Defending against near-Earth asteroids has become an emerging focus and frontier in deep space exploration.The current status of international organizations such as the United Nations,as well as countries including the United States,Europe,and Russia,was systematically investigated in terms of management systems and technological frameworks for near-Earth asteroid defense.The current state of China's defense system was reviewed,future development goals were discussed,and key development directions,including monitoring and early warning,on-orbit mitigation,disaster response,and routine system preparedness,were proposed,providing reference and guidance for building China's near-Earth asteroid defense system.

The impact of near-Earth asteroids (NEAs) poses a major potential hazard to humanity. Among the various planetary-defense strategies, the kinetic impact method is currently regarded as the most practical approach due to its demonstrated effectiveness and relatively mature technological readiness. In 2022, the United States carried out the on-orbit Double Asteroid Redirection Test (DART), successfully altering the orbital period of the secondary component in a binary asteroid system, marking a significant milestone in planetary defense. However, most NEAs are single bodies on the scale of several tens of meters. These small asteroids have a higher impact frequency and, if they impact Earth, are capable of causing city-level damage, thus representing a more immediate and realistic threat to human society. In this study, we propose an on-orbit test mission concept for kinetic impact-based mitigation targeting small, single NEAs. The proposed mission architecture is derived from analyses of mission requirements, mission system-level design, target-selection criteria, trajectory-optimization strategies, and post-impact deflection simulations. First, four mission design principles are formulated through a systematic review of the mission requirements. Second, an overall mission concept is developed involving a dual-spacecraft launch profile, in which a precursor observer spacecraft performs early rendezvous and characterization of the target, followed by a dedicated impactor spacecraft that subsequently executes the high-velocity collision. Based on the design principles, we establish a set of target-selection criteria that consider the asteroid's physical properties, orbital characteristics, observability conditions, and safety. To address the constraints associated with simultaneous launch, sequential arrival, and the differing relative velocities required for rendezvous and impact, we analyze feasible mission windows and propose a trajectory strategy that employs Earth-elliptical phasing orbits for initial transfer in Earth-moon space and a Venus gravity-assist maneuver for deep-space transfer. This approach effectively decouples the transfer trajectories of the observer and impactor, ensuring that both spacecraft meet their respective timing and dynamical constraints. We further conduct detailed simulations of the mitigation performance by considering different asteroid material properties and different impact angles. The simulations yield corresponding impact-response outcomes and allow us to evaluate the deflection distance and the medium-to-long-term evolution of the post-impact trajectory under various parameters. Coupled dynamical analyses indicate that the proposed kinetic-impactor mission concept can induce a meaningful orbital change-or potentially structural disruption-for a monolithic NEA with a diameter of approximately 30 meters, thereby demonstrating the feasibility of validating kinetic-impact mitigation strategies for small NEAs. The mission concept and associated analytical results presented in this paper provide a valuable reference for the design and implementation of future on-orbit test missions aimed at enhancing planetary-defense capabilities.

Orbital pursuit-evasion games (OPEG) have attracted growing academic interest owing to their significance in the domain of on-orbit servicing. However, existing solutions for impulsive OPEG often suffer from limited interpretability and algorithm stability. To overcome these limitations, this paper proposes a heuristic tree search method augmented with motion characteristics. Different from the existing methods, this study focuses on the description of the orbital dynamics information in the OPEG process and how it can be introduced into the algorithmic mechanism of tree search for the first time. By constructing quantitative reward functions that represent orbital motion characteristics, key motion information is introduced as heuristic factors into the Monte Carlo tree search (MCTS) framework, aiming to guide the tree search and prioritize the exploration of more promising maneuver spaces. Compared with the random strategy adopted by the standard MCTS during node expansion, the proposed heuristic tree search framework can generate optimal maneuver decisions more stably within a limited search time. In this study, the performance of different algorithms is comprehensively evaluated in terms of capture success rate, number of game rounds, and terminal relative distance. Simulation results show that, compared to the standard MCTS, the proposed heuristic tree search method enables the pursuer to achieve fewer game rounds and shorter terminal relative distances at the end of the game while also exhibiting greater decision stability across multiple repeated experiments. In addition, extended experiments are conducted under a three-dimensional orbital dynamics model, further showing that the proposed method has the potential to be adapted to multi-degree-of-freedom space mission scenarios. (c) 2025 Published by Elsevier B.V. on behalf of COSPAR.

The Lunar Orbital VLBI Experiment (LOVEX) is a scientific component of the Chinese Lunar Exploration Project (CLEP) Chang’E-7. The spaceborne component of LOVEX is implemented onboard the relay satellite QueQiao-2, which was launched on 20 March 2024, and later placed into an elliptical selenocentric orbit. The LOVEX-specific payload consists of an X-band cryogenic receiver, a hydrogen maser frequency standard, and VLBI data formatting and acquisition electronics. Several components of the QueQiao-2 nominal onboard instrumentation, such as the 4.2-m antenna, the data storage device, and the downlink communication system, contribute to the overall spaceborne VLBI instrumentation. This allows us to form a space radio telescope capable of co-observing with Earth-based radio telescopes in VLBI mode. In this space VLBI system, the length of the baseline extends up to approximately 380000 km. This paper presents the LOVEX scientific objectives, architecture, instrumentation, prelaunch tests, in-flight verification and calibration, and the first in-flight detections of interferometric response (“fringes”) achieved through observations of the quasar AO 0235+164 and the Chang’E-6 orbital module, positioned at the Sun-Earth Lagrange point L2. These initial results demonstrate the successful performance of LOVEX, verifying its capability for both astronomical and spacecraft tracking observations at ultra-long VLBI baselines.

Owing to the large communication delay in deep space exploration missions, trajectory maneuvers prior to the flyby of small celestial bodies generally need to be scheduled in advance. However, the lack of prior data and the presence of environmental uncertainties in deep space are significant challenges for maneuver scheduling. To solve this problem, in this study, robust maneuver scheduling networks based on proximal policy optimization were proposed. A reward function that considers the terminal state accuracy of the spacecraft after maneuvering and the total velocity impulse cost was designed for the maneuver scheduling networks. An additional constant was added to the variance of the actor network to improve the performance of the generated maneuvering strategy. Compared with the actor-critic algorithm and genetic algorithm, the maneuvering strategy generated by the maneuver scheduling networks demonstrated the best performance in most simulation scenarios and maintained a better balance between the terminal state accuracy and the total velocity impulse cost. The robustness of the maneuver strategy against uncertain perturbations in the environment and uncertain initial state deviations of the spacecraft was validated in several maneuver scenarios in the simulation. In addition, the generated maneuvering strategy exhibited excellent real-time performance. The time cost to make a decision was still better than 0.7 s in the worst case, testing on Raspberry Pi 4B with a memory of 4 GB and a limited CPU frequency of 800 MHz. The robustness against uncertainties and real-time capability of the proposed method revealed its potential onboard application to future deep space exploration missions.

Deep space exploration expands our understanding about the evolution history of solar system, while the future development heavily relies on the construction of energy systems and utilization of resources on the planet. This paper systematically reviewed the progress in the environmental control and construction technologies of space bases, extraterrestrial in situ resource utilization technology, energy systems, key technologies for planetary transportation platforms, and geological explorations. The current status, pros and cons of these technologies and systems are introduced and discussed. As an important artificial microenvironment in the space base, the environmental control and life support system (ECLSS) provides necessary resources for human. Sintering and additive manufacturing technologies demonstrate the potential to construct a space base with lunar regolith or simulants. The extraction and in situ utilization of resources on the Moon, including water ice, oxygen, and helium-3, are crucial to maintain life support for lunar exploration. Typical energy systems that can be used on the Moon include photovoltaic cell, Stirling power generation technology, closed Brayton cycle (CBC) system, Rankine cycle system, heat storage system, and integrated energy system. The CBC system has the highest thermal efficiency (39%) among them, making it suitable for late-period energy supply. The performance of various planetary rovers, the most important transportation platforms, are summarized. Through geological explorations, the resource distribution, content, and occurrence can be obtained. Perspectives on the future, promotions of environment adaptation, resource recovery, energy efficiency, and intelligence of the existing technologies are still needed to move forward on space explorations.

In deep space telemetry tracking and command (TT&C) missions, the low signal-to-noise ratio (SNR) of the receiving signal restricts the improvement of measurement performance. In the article, we adopt the uplink signal which transmitted by the ground station to achieve very long baseline interferometry (VLBI) in the spacecraft. Notably, this methodology guarantees an SNR enhancement of at least 30 dB compared to the downlink signal, marking a significant improvement. Considering the restrict of spacecraft calculate resources, we adopt multiple baselines to simplify the VLBI method in spacecraft receiver and obtain the high accuracy angle measurement results. The simulation and analysis show that the algorithm achieves a measurement accuracy of 0.77 nrad on the baseline length of 74 km, while the accuracy of traditional delta differential one-way ranging (Delta DOR) observations is 1 nrad with an 8400 km baseline length. In addition, we design a hardware platform for algorithm verification. This platform, under real-world conditions, exhibits an angle measurement error of less than 5 mrad even with a baseline length as short as 0.74 m.

This study explores a new navigation method using multi-path solar panel-reflected solar oscillations. Considering the solar panels of BeiDou-3 M1–M24 and GPS satellites as examples, the simulations show that the mean position error of FY-1 using solar panel-reflected solar oscillations is only 20.61 m in 30 days. Compared with the existing autonomous navigation methods for the Earth satellites, the newly proposed method has two advantages. (1) It has the highest navigation accuracy. (2) It does not require any additional accurate geomagnetic map, gravity gradient map, or refraction model. While the proposed method requires at least two atomic frequency discriminators to obtain the measurements and its accuracy is affected by the geometric relationship between the Earth satellite, reflected satellite, and Sun, which are the inherent drawbacks of the method. It is notable that the influence of the relativistic effects on the measurement accuracy needs further research.

Deep space exploration is one of the frontiers of scientific research and driven by human instincts to explore the unknown. Since the Moon Race in the 1960s and 1970s, deep-space probes have explored many celestial bodies in our solar system, including eight planets. These explorations have yielded tremendous scientific discoveries, but they also revealed many more unsolved mysteries. The 21st century has witnessed a remarkable increase in deep-space exploration activities, with several new agencies launching their spacecraft in the past few decades. As a result of technological advancement, exploration success rates have improved significantly. A systematic review of frontier scientific questions can provide invaluable references for mission planning strategies and boost scientific discoveries and breakthroughs in the future. In general, these questions are related to three primary scientific subjects: (1) One of the primary scientific objectives of deep-space exploration is to study the origin and evolution of the solar system. From the collapse of the solar nebula to the formation of the planetary system, the solar system has undergone a complex evolutionary process. The components of the current solar system, particularly the residual presolar material, can provide critical information for understanding the initial conditions and evolution of the solar system. The Moon, being the nearest celestial body to Earth, serves as an outpost for exploring other planetary bodies and is especially important for testing deep-space exploration equipment and studying solar system evolution. (2) Another objective of deep space exploration is to better understand the evolution of planetary habitability. The Sun is an important factor affecting habitability, and eruptions of solar activities can have a substantial impact on the space environment of the solar system. The environment of the Earth and other planets has changed dramatically over billions of years of evolution. Although life has only been confirmed on Earth, other celestial bodies might also have had habitable conditions along the evolutionary process. Decoding the evolution of the habitable environment of solar system planetary bodies is of great significance for understanding the formation and evolution of habitable Earth and the origin of life on Earth. (3) Extraterrestrial life detection is a critical scientific topic in deep space exploration, with far-reaching implications for understanding the origin, evolution, and distribution of life in solar and extrasolar systems. The current scientific challenges in the detection of extraterrestrial life primarily involve four aspects: the origin and evolution of life, extraterrestrial habitable environments, life signal identification, and analogy of terrestrial extreme environments. In endeavors to answer these scientific questions, more well-planned deep-space exploration missions are required to collect evidence. In order to outpace opponents in the continuing space exploration endeavor, the National Aeronautics and Space Administration (NASA), the European Space Agency (ESA), and other rising roles have made their ambitious roadmaps. NASA will encourage commercial companies to join future missions through the Artemis program, and has planned missions to explore Venus, asteroids, and icy bodies. The ESA proposed tens of missions in its white paper Voyage 2050. In the coming decades, China will lay the groundwork for the International Lunar Research Station through three Chang’e and four Russian Luna missions. Furthermore, Tianwen-2 and Tianwen-3 will return samples from asteroids and Mars, respectively; Tianwen-4 is intended to explore the Jupiter system. The success of these missions will yield unprecedented information for deciphering the mysteries of the solar system and life, as well as considerably expanding our knowledge of the universe we live in.

>The traditional strapdown inertial navigation system(SINS)/celestial navigation system(CNS) integrated navigation system using the starlight vector or posture difference calculated by SINS and CNS as a measurement can correct the posture error of SINS, but not the position error [1]. The refraction celestial navigation system(RCNS) can independently provide the position information.

Near-Earth asteroid impact is a major catastrophic threat facing human society. Planetary defense is an inevitable requirement for building a community with a shared future for mankind and continuing human civilization. Implementing on-orbit disposal is the best way to prevent and resolve the risk of near-Earth asteroid impact. This paper systematically combed the development status of near-Earth asteroid defense on-orbit disposal technologies, comprehensively summarized the key technologies, advantages and disadvantages, and application scenarios of nuclear explosion, kinetic impact, gravitational traction, ion beam, laser ablation, tug, mass driver, surface spraying and other on-orbit disposal technologies, and puts forward suggestions for the development of near-Earth asteroid defense on-orbit disposal technology.

In response to the urgent needs of deep space explorer for autonomous celestial navigation，this paper briefly introduces the research status of autonomous celestial navigation methods and summarizes the problems faced by current autonomous celestial navigation methods. As the error sources of the celestial navigation system is multiple and time-varying，two error suppression technologies based on augmented filtering and differential are expound in detail. In view of the limitations of the existing autonomous celestial navigation methods，the autonomous celestial integrated navigation methods are introduced in detail. Finally，the future development trend of the celestial navigation method for the deep space spacecraft is prospected.

Libration points are vital for lunar and deep space explorations because of their unique positions and dynamics. This paper first traces the development of relevant missions since ISEE-3 and then presents the details of the trajectory design and implementation of four Chinese libration point missions in the lunar exploration project: the two Sun-Earth libration point missions by CHANG’E-2 and CHANG’E-5 and the two lunar libration point missions accomplished by CHANG’E-5T1 and Queqiao. The orbit technologies for these libration point missions are also elaborated on regarding trajectory design, maneuvering, and tracking, as well as orbit determination. This paper is expected to provide a reference for future cislunar and deep space exploration.

In a multi-node spacecraft or unmanned aerial vehicle (UAV) group, a multifunctional signal containing measurement, navigation, and communication functions is required to simplify the receiver structure, and to increase spectrum utilization. The paper proposes a multifunctional signal based on a binary offset carrier (BOC) and binary phase shift keying (BPSK) modulation. The signals which carry different functions are orthogonal in the frequency domain, which causes the data transmission signal to not be affected by BOC signal. In addition, in the high carrier to noise ratio (C/N-0), the spreading gain of the BOC signal ensures that the communication signal has a slight influence on navigation signals. Moreover, the multifunctional signal can achieve communication and measurement functions at the same frequency point and fast switching in multinodes. These advantages can simplify the receiver design and improve the frequency band utilization. Finally, in this study we completed the design and verification of the hardware system.

As deep space exploration activities increase worldwide, the exploration environment becomes increasingly complex and the exploration tasks become increasingly difficult. Therefore, it is of great practical significance to research on deep space security issues. In this study, we first clarify the basic connotation of deep space security, briefly describe the significance and key issues of deep space security research, and summarize the research status and future development of four key deep space security issues: space radiation threat, planetary protection, space heritage protection, and space legislation. The study indicates that space radiation has the characteristics of multiple threat sources and high radiation intensity and should be researched from the perspectives of physical, biomedical, and chemical protection. Planetary protection mainly faces the challenges of pollution and impact of deep space spacecraft, and research should be conducted from the perspectives of deep space microbial detection and disinfection technologies as well as policy formulation. Space heritage protection is controversial in terms of evaluation and protection measures owing to political, cultural, and legal differences among countries, and it should be researched from the perspectives of international cooperation, deep space spacecraft, and reduction of human impact. Due to the complex international relations among countries, it is difficult for the effectiveness of current laws and regulations to become the consensus of the international community; therefore, research should be conducted from the aspects of international legislative organizations, domestic research institutions, and the improvement of domestic legal systems.

For deep space exploration, a short-period pseudo noise (PN) ranging code cannot be applied due to the extremely large distances, whereas a long-period spread spectrum ranging code is also limited in application due to the long acquisition and tracking times. Under these circumstances, this letter proposes a parallel composite code upgrade from the traditional serial composite code. This proposed scheme can simplify the hardware structure and improve the unambiguous distance. The ranging method can complete unambiguous acquisition and tracking within 613674 km under the condition of an acquisition sensitivity of −156 dBm.