On May 29, 2025, China successfully launched the Tianwen-2 spacecraft to conduct a sample-return mission, targeting the near-Earth asteroid (469219) Kamoʻoalewa. Here, we systematically review early works on Kamoʻoalewa from various research teams, synthesizing reported results on its orbital characteristics, dynamical origin, composition, spectral type, size, rotation period, axis orientation, global regolith particle size distribution, regolith thickness, potential evolutionary history, and key scientific questions. We also predict space weathering features of future returned samples.
A trajectory planning algorithm combining Radau pseudospectral method and convex optimization method is proposed for the problem of small celestial body landing trajectory planning. The pseudospectral method uses non-uniform nodes and Lagrangian difference polynomials to approximate variables, providing a discretization method for continuous time Non-Linear Programming (NLP) problems. By constructing and convexifying the optimal control problem for segmented small celestial body landing trajectory planning, and discretizing the obtained convex optimization problem for small celestial body landing trajectory planning by the Radau pseudospectral method, a pseudo-spectral sequence convex optimization solution method for small celestial body landing trajectory planning with segmented state constraints is proposed. This method can simultaneously obtain the exponential convergence of Radau pseudospectral method and the fast solving speed of convex optimization method, and has high solving accuracy. Through simulation verification, the feasibility and effectiveness of the algorithm in autonomous landing of small celestial bodies have been demonstrated.
This study investigates dust eruption dynamics in the near-nucleus region of icy small bodies. To resolve the computational limitations of existing models, we extend Fink et al.'s (2021) one-dimensional simplified framework into three dimensions, simultaneously incorporating nucleus rotation effects (centrifugal/Coriolis forces) and eruption scales (global vs. local). Our approach establishes unified 3D dynamical models for both globally distributed dust-gas eruptions and localized eruptions with constrained source areas. Through numerical simulations parameterized with comet 67P/Churyumov-Gerasimenko's physical properties, we quantitatively examine dust particle lifting thresholds, trajectory evolution, and landing distribution patterns. Simulation results reveal that: (1) the critical lifting radius of dust particles decreases with increasing latitude; (2) the particle size profoundly influences their trajectories and ultimate dynamic behavior; (3) due to the nucleus rotation, a notable systematic north-south offset appears in dust landing points during global eruptions, while this offset is weaker in localized eruptions due to the constrained source scale. These results provide a theoretical foundation for predicting dust environment evolution around icy small bodies and assessing impact hazards for deep-space exploration missions.
Three-dimensional (3D) models of small celestial bodies are crucial for revealing their morphology, dimensions, and surface characteristics, providing essential dataset for both exploration tasks and scientific research. Current high-resolution modeling relies on close-range observation by space probes, with traditional techniques such as stereo photogrammetry and photoclinometry (or shape from shading) being widely used. While stereo photogrammetry reconstructs 3D geometry depending on surface texture quality captured on the stereo images, photoclinometric methods exploit pixel-wise brightness to recover fine topographic details. This paper presents a synergistic pixel-wise reconstruction method that integrates stereo photogrammetry and photoclinometric optimization. The method includes three key steps: Firstly, a relatively low-resolution 3D model is constructed using stereo photogrammetry. Secondly, the global model is partitioned into localized regions for iterative photogrammetric refinement. Finally, optimized local regions are merged into a global model of higher resolution and accuracy. Validation experiments conducted using images of a 3D-printed model of asteroid Bennu within an indoor test site revealed that the proposed method can achieve high geometric accuracy and reconstruct subtle terrain features. This integrated method enables high-fidelity modeling of small celestial bodies, supporting the Tianwen-2 mission and related scientific research.
The spin-axis orientation and shape parameters of near-Earth asteroids are critical reference information for studying their formation and evolutionary history, as well as for conducting in-situ space exploration. With the continuous advancements in time-domain astronomy and deep-space exploration technologies in China, an increasing number of universities and research institutions are actively constructing observational facilities which can support near-Earth asteroid observation and research. In this study, a sun-Earth-asteroid physical and dynamical model was established, considering near-Earth asteroids with different triaxial ellipsoid shapes. Simulated light curve data were utilized to investigate the parameter space necessary for inverting the spin-axis orientation and shape of asteroids. Periodograms were extracted from the light curves using the Lomb-Scargle and phase dispersion minimization methods, and a global fitting procedure for asteroid inversion parameters was developed. The results show that with a photometric accuracy of 0.001, 4~6 light curves covering 10° of solar phase angle are sufficient for inversion. For a photometric accuracy of 0.010, 8~10 light curves covering 20° of solar phase angle are required. At a lower photometric accuracy of 0.100, continuous observations covering multiple full rotation periods are recommended initially, followed by sparse observations to extend the solar phase angle for further confirmation of the inversion results. Additionally, for asteroids with nearly equal short axes, the required solar phase angle range can be moderately relaxed. This study provides a reference for the inversion of near-Earth asteroids using light curve data and offers methodological guidance with China’s existing and upcoming ground-based and space telescopes.
Deep space probes typically operate at vast distances from Earth, leading to prolonged communication delays and significantly reduced real-time monitoring and control capabilities. In many cases, telemetry data cannot be downlinked or can only be transmitted at extremely low rates. Therefore, deep space probes must possess autonomous fault diagnosis and long-term operational capabilities to reduce dependence on ground-based telemetry analysis. Under limited downlink conditions, it is essential for probes to transmit critical health status information in a timely manner to support ground-based flight control. Considering that the onboard computer system of deep space probes adopts a hybrid centralized-distributed architecture, this paper proposes a hierarchical approach to fault diagnosis and recovery at the module level, device level, and system level. This multi-level strategy enables multi-dimensional fault detection, which reduces the probability of missed or incorrect diagnoses. It also facilitates collaborative fault diagnosis and recovery among multiple subsystems, maximizing the utilization of onboard resources. This work lays a foundational methodology for future research and development in fault diagnosis and recovery for deep space onboard computer systems.
This paper focuses on China’s first asteroid exploration mission. In accordance with the single-unit functional requirements of the payload management unit for the Tianwen-2 probe, it introduces the unit’s composition design, operating modes, and single-unit functions. This device ensures the power supply and distribution safety of the subsystem through designs such as power fault isolation. It enhances the system’s fault tolerance capability by means of on-orbit updatable and customizable status monitoring, fault recovery processing, and other measures. Relying on autonomous detection, it achieves precise mission switching and autonomous mission planning. Moreover, through data management designs like joint detection and scientific data preprocessing, it improves the efficiency of scientific detection. Ultimately, it enhances the reliability of the payload system, realizes integration, autonomy, and high efficiency, and lays a technical foundation for the design of payload systems in China’s subsequent deep-space exploration missions.
Studying the exposure age of asteroids is crucial for understanding their formation and evolution. The implementation of the Double Asteroid Redirection Test (DART) mission demonstrated the feasibility of using kinetic impact to deflect the trajectory of a near-Earth asteroid and also provided a valuable opportunity to investigate the exposure age and evolutionary processes of Didymos. This study investigates the exposure age of the surface of the primary asteroid Didymos and the ejecta of the secondary asteroid Dimorphos, based on visible and near-infrared spectral data obtained by ground-based telescopes before and after the DART impact. It shows that the exposure age of Didymos surface is approximately 457 thousand years, implying that the primary asteroid experienced a significant rotational fission event about 457 thousand years ago. This event had almost no effect on the surface age of the primary asteroid but reset the surface age of the secondary asteroid and the exposure age of the primary asteroid. The ejecta of Dimorphos share the same composition as the surface of Didymos but exhibit a lower degree of space weathering, suggesting that after the formation of the secondary, the surfaces of both the primary and the secondary underwent intense space weathering, while the material from the interior of the secondary was relatively less affected.
As a unique type of celestial body, asteroids possess significant scientific research value and resource development potential, while also posing potential extraterrestrial impact threats, which have important implications for human civilization and planetary safety. The distribution characteristics of boulders on the surface of asteroids are crucial for understanding their formation, evolution, and physical properties. However, due to the small size, large quantity, and low quality of images of asteroid surface boulders, traditional methods face challenges in accurate statistical analysis. To address these issues, this study introduces an instance segmentation algorithm based on YOLOv8 to improve the detection and segmentation performance for asteroid surface boulders, especially by enhancing the model's ability to detect small-scale boulders through the addition of a small-object detection head. Furthermore, the Slicing Aided Hyper Inference (SAHI) framework is integrated to perform slice-based inference on high-resolution images, thereby enhancing both inference efficiency and segmentation accuracy on large-scale images. Subsequently, geometric analysis techniques, such as ellipse fitting, are employed to extract spatial location, size, and orientation information of boulders from the segmentation results. Finally, the proposed method is applied to the analysis of boulder distribution on the surface of asteroid Bennu. The results indicate that the surface boulders exhibit certain spatial distribution patterns, demonstrating the effectiveness and applicability of the proposed approach in practical planetary image processing tasks.
The Tianwen-2 mission will investigate the internal structure of the near-Earth asteroid 2016 HO3 with a monostatic radar system. In preparation for the processing of monostatic radar data, this study proposes a three-dimensional (3D) Full-Waveform Inversion (FWI) method for reconstructing the internal structure of asteroids using monostatic radar data. We first validate the feasibility and effectiveness of the proposed method using a 3D two-layered onion-shell asteroid model. Subsequently, we systematically examine the influence of three key parameters of radar acquisition geometry (including the number of orbits, the number of radar measurement points, and the spacing of adjacent orbits) on the FWI performances. Our analysis demonstrates that reliable reconstruction can be achieved when the acquisition geometry comprises 3 orbits with an inter-orbit spacing of 25~35 m and at least 20 measurement points per orbit. This study not only provides a high-accuracy inversion methodology for the processing of monostatic radar data, but also offers scientific guidance for designing radar acquisition geometry in the ongoing Tianwen-2 mission.
The enantiomers of chiral drugs have different physiological activities, and the external environment may lead to the racemization of a single enantiomer, which may result in the weakening or even loss of its biological activity. Although NASA and other organizations have studied the effect of space radiation on drug stability, the studies on the stability of chiral drugs are still limited. Flavonoids, as active chiral components of traditional Chinese medicine that are homologous to food and medicine, have potential space applications for the prevention and treatment of diseases. Therefore, in this study, chiral compounds of flavonoids were carried by manned spacecrafts and returned satellites, and chiral liquid chromatography analysis was utilized to investigate their chiral stability in the space environment. The experimental results showed that some of the flavonoid chiral compounds were stable in the space environment for up to one year of storage due to the substituent group types and stereochemical structure differences, while hesperidin and flagellin underwent different degrees of chemical degradation or chiral changes. The study in this paper provides a theoretical basis for the stability and structural protection of chiral drugs, as well as data support for the study of astronauts’ food and drug health in space.
Ground-based planetary radar can obtain the physical characterizations including precision orbit, rotation, topography of the asteroids by transmitting electromagnetic signals actively and receiving the echo signals from asteroids, it is crucial for near-Earth asteroids defense and planetary science. The research of ground based planetary radar is currently focused on Deep Space Array Planetary Radar (DSAPR). An overview of the development of DSAPR technology is presented in this paper, and the current status and trends of array radar technology is reviewed, including the Goldstone uplink array radar, Ka Band Array Radar for Near-Earth Objects Accurate Characterization, Deep space Advanced Radar Capability, China Compound Eye and downlink array technology. The state of the antenna array at Kashi Deep Space Station is introduced, and the technical advantages of the deep space array planetary radar based on the multi-antenna of the Kashi Deep Space Station are analyzed. Finally, the detection capability of the 4×35 m and 20×35 m DSAPR formed by the expansion of the Kashi Deep Space Station antenna array is analyzed.
Scientific data and extraterrestrial samples are core outcomes of deep space exploration activities and have irreplaceable research value. International cooperation centered on the sharing of scientific data and extraterrestrial samples has become a common practice in international cooperation for deep space exploration missions. With the rapid growth of deep space exploration missions, relevant technology has been continuously enriched, and related rules are gradually formulated. This paper analyzes existing international space laws and relevant rules, studies the policies and practices of sharing scientific data and samples in deep space exploration of major space faring countries around the world, and puts forward some suggestions for China's related work.
Aiming at the short-term hazard assessment requirement of the satellite breakup event in constellation, a short-term hazard assessment algorithm of fragmented debris cloud based on boundary value problem is proposed. The spread velocity of the debris is obtained by solving the two-point boundary value problem, and the joint probability distribution density function of spread velocity and characteristic size is derived by using of the CSBM model. On this basis, the mathematical representation of collision risk of debris cloud with specific size is obtained. The algorithm is applied to the short-term hazard assessment of constellation satellite breakup scene. The results show that the impact risk of debris cloud is highly concentrated on coplanar satellites and some out-of-plane satellites intersecting with them at high speed. This kind of satellite has high collision risk when periodically crossing debris cloud and reaches the maximum at the first crossing. The collision risk of other satellites gradually accumulates with the spread of debris cloud, but the risk is lower. The proposed algorithm and related conclusions can provide support for short-term hazard assessment of breakup events
