The research and development of key technologies of manned lunar bases home and abroad were summarized in this paper. The landmark events and achievements of lunar exploration and lunar base research were studied. The four basic principles of lunar base construction were proposed, based on which the overall planning scheme and six major systems of the manned lunar base located in the polar region of the moon were developed. In addition, a number of key technologies were extracted from the aspects of lunar resource exploration and development, energy utilization and environmental control, life and health, lunar surface communication and intelligent technology, carrying and transportation, operation and maintenance and simulation. Finally, based on the research status of key technologies and the actual needs of the construction of lunar bases, the shortcomings of this research were summarized, to provide suggestions and prospects for the construction, operation and maintenance of future manned lunar bases.

Based on the requirements on the structural and functional materials used for the construction of lunar base, this paper discusses the feasibility of using lunar soil to prepare corresponding fibers to achieve this ambitious goal, and the latest progress in this field is reviewed. The unique advantages and application prospects of lunar soil fibers for structural protection, survival and life support in the lunar bases are then analyzed. Finally, theoretical and technological issues for future research and breakthroughs in the development of lunar fibers are proposed, in an effort to promote the prosperity of this promising field in both fundamental and applied research.

Space-based monitoring and early warning of Near-Earth Asteroids (NEAs) is an important development direction for future planetary defense. Cooperative space-and ground-based observations can give full play to the advantages of space- and ground-based telescopes and improve the efficacy of the system as a whole. In this paper，a model of near-Earth asteroid observation was formulated，a scheme of space-based observation system for Sun-Earth L1 point orbit was analyzed and designed，and an efficacy evaluation method was proposed. The cooperative observation efficacy of the Sun-Earth L1 point orbit observation system was simulated and evaluated based on the potentially hazardous asteroids database. The relevant early warning efficacy was calculated and analyzed，and the design concept of regional and time-domain divided collaborative observation was proposed. This paper provides importance reference for future evaluation of the efficacy of different space-based observation systems and the study of space- and ground-based cooperative observations. The preliminary simulation results show that the infrared and visible systems of the Sun-Earth L1 point orbit can achieve 49.4% and 38.2% cataloging completeness of the potentially hazardous asteroids in 1 year with a limited apparent visual magnitude of 22，and both can carry out the monitoring mission well；after cooperative observation with ground-based station，the completeness rate of the corresponding cooperative system can reach 58.9% and 50.6%，respectively， which is 1.19 times and 1.35 times that of the completeness rate before，indicating that cooperative observation can effectively improve the observation efficacy of the system.

The manned lunar research station is an important basic facility for achieving medium- and long-term deep lunar exploration, and at the same time is a system project with multiple complex challenges. In this paper, from an architectural perspective, design constraints at macro, meso, and micro levels were analyzed first, and an implementation method for the architectural design of the manned lunar research station was provided using systems engineering, which consisted of four dimensions: the overall goal is “safety, sustainability, and intelligence”; the application ideas included process integration, model visualization, and design modularity; the application advantages are high efficiency, accuracy, and integration; the application framework was divided into application layer, model layer, and data layer. Finally, a three-dimensional structural model of architectural design system engineering was constructed, which included time dimension, logic dimension and knowledge dimension, and comprehensively embodied the structure of each task and related scientific knowledge in each stage, aiming to provide new perspectives and new ideas for the construction of manned lunar research station.

The high precision spacecraft platform system is an important carrier and plays a significant role in the successful implementation of a space gravitational wave detection mission. In this paper, frontier researches on high-precision spacecraft platform systems were reviewed and summarized. The inertial sensor reference of spacecraft platform, micro-thrust actuator, drag-free attitude control technology of spacecraft platform, formation design and control of spacecraft system were discussed. The recent relevant research progress of spacecraft platform system used for space gravitational wave detection was summarized and discussed, covering both domestic and international frontier research hotspots, focusing on key research issues of space gravitational wave detection spacecraft platform system design. A prospect on the development of spacecraft platform system was proposed, including key payloads, orbit and attitude control strategies, formation configuration design, etc

The micro-vibration of ultra-high-static and ultra-high-stable spacecraft was studied. A modeling and simulation method was proposed to introduce the pointing measurement error and additional torque error induced by micro-vibration into the pointing measurement control system. The micro-vibration experiment of the pointing measurement system was carried out based on the quasi-zero stiffness suspension method. The simulation and experimental results show that the pointing measurement error induced by micro-vibration was more significant, and the peak value reached 10e-4°, and the pointing measurement error of the pointing control system caused by micro-vibration was 0.03 pixels. This work can be used for reference in the study of ultra-high-static and ultra-high-stable spacecraft and derivative technologies.

Lunar water and other volatiles in permanently shadowed regions are not only key elements to studying the early history of the Moon and solar system, but also important sources for in-situ resource utilization for future lunar base construction. In this study, we compute the illumination rate of 2026 and slopes within a 15 × 15 km area near the lunar south pole based on the 20 m/pixel digital terrain model (DEM). We propose to use the illumination rate and slope to constrain landing area selection based on a finer map meshing within the study area and find that the distribution of potential landing areas varies with different constraints. We also extend the study area to polar regions ($ > 88.5^{\circ} $) based on the 60 m/pixel illumination rate map and DEM data. The result shows that there are 8 potential landing areas including three at the Shackleton crater rim, two at the de Gerlache crater rim, two at the ridge between the former two craters, and one at the ridge between the Shackleton and Slater craters. Our study provides candidates for future polar landing missions and a method for landing site selection from higher DEM data.

In this paper, a space-based orbit determination and time synchronization method for Earth-Moon spacecraft was presented. As a “space-based tracking station”, LEO satellite on the one hand receives GNSS navigation signals to achieve high-precision real-time orbit determination and timing；on the other hand, it establishes measurement links with Earth-moon space spacecraft to support the fast and high-precision orbit determination of Earth-moon spacecraft. Compared with ground stations, LEO satellites operate at a faster speed and orbit the Earth in a shorter period. The Earth-Moon spacecraft and its measurement link have the advantages of short invisible time interval, better measurement geometry, and no atmospheric delay in the measurement process. Therefore, using LEO satellite can improve the convergence speed and accuracy of orbit determination. This paper analyzed the space-based orbit determination and time synchronization performance of three typical orbits in Earth-Moon space, including the distant retrograde orbit (DRO), the highly elliptical orbit (HEO) and the Earth-moon transfer orbit. Space-based orbit determination simulation results show that when the LEO satellite position accuracy is high, the convergence time of the three orbits is less than 3 hours, the orbit position accuracy is about 50 m, and the time synchronization accuracy is tens of nanoseconds. Therefore, this method can hopefully solve the problems of limited deployment and heavy burden of ground stations.

In view of the threat of more frequent near-Earth asteroid impacts，the asteroid dynamic push away deflection disposal mission was demonstrated. The disposal method was pushed away the asteroid multiple times by penetrating and anchoring the asteroid surface and by electric propulsion. In this paper，a dynamic model of near-Earth asteroids was established to study the change of orbit deviation of asteroids with different rotation states under the dynamic push away treatment strategy. Taking the deflection of 2019VL5 asteroid as an example，the efficiency of dynamic push away disposal and the feasibility of the project were evaluated by numerical simulation. The simulation results show that during the warning time of 4 years the maximum deflection distance of the asteroid could be 2.91 × 10⁴ km under the small 0.4 N thrust applied to the specific orbital position，and the maximum deflection distance of the asteroid could be 9.0 × 10⁴ km after 2 500 days of disposal. The dynamic push away disposal of asteroids can effectively deflect threatening asteroids，and can be used in future asteroids deflecting defense missions and orbit transfer missions against other space object attacks.

With the continuous progress of human society and the rapid development of aerospace science and technology, cislunar exploration and exploitation is entering the stage of large-scale and industrialization. Cislunar aerospace transportation system is an important component of large-scale cislunar exploration and exploitation, supporting various activities of cislunar exploration and exploitation. Firstly the global development status and trends of cislunar aerospace transportation are introduced in this paper. Then the composition of the cislunar aerospace transportation system is given, and the capacity demands in the future are predicted based on an analysis of future development needs. Facing to the large-scale and low-cost cislunar aerospace transportation in future, One-stop solution and Relay-style solution are proposed. At last according to the typical mission requirements of lunar landing and return, the propellant refueling and system scale requirements of two solutions are analyzed. The paper will provide reference for cislunar aerospace transportation system development.

The lunar South Pole region’s limited illumination, extensive shadowed regions, and homogenous surface features with weak textures pose significant challenges to stereoscopic image matching and 3D terrain reconstruction. To address these issues, an Efficient Confidence-guided Stereo Matching (ECSM) algorithm was proposed. This algorithm improved matching precision and efficiency by assessing the confidence of non-support points, updating the support point dataset, constructing a triangulated mesh, and recalculating disparities within triangle vertices based on their confidence levels. On this basis, a photogrammetric method for lunar 3D terrain reconstruction was established. High-resolution image data from the Lunar Reconnaissance Orbiter’s Narrow Angle Camera was utilized for validation experiments conducted in the vicinity of the Shackleton crater within the lunar South Pole region. Qualitative and quantitative analyses of disparity maps and Digital Elevation Model (DEM) generated from different stereo matching algorithms demonstrated the reliability of the proposed algorithm in regions with weak and repetitive textures. Comparative analyses with the German Aerospace Center’s DEM and NASA’s Lunar Orbiter Laser Altimeter DEM (LDEM) for the same region revealed significant consistency in elevation and slope information, affirming the practicality and effectiveness of the proposed method. This study provides a methodological foundation for landing site selection for lunar South Pole explorations.

Research on the grading of impact risk is an important prerequisite to dealing with the danger of impacts by near-asteroids. In this paper，a new risk-grading method was proposed to estimate the risk of near-Earth asteroid impact. The hazard forms and consequences of near-Earth asteroid impact were analyzed，and the factors of impact risk classification were sorted out. The relatively mature Torino scale model and Palermo index model were discussed，and the equivalent diameter and impact probability were taken as the main factors to design the impact risk grading method. A refinement of partition model of risk grade was established. Finally，the simulation comparison and analysis were carried out for different risk grading models.

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 recent years, international lunar exploration has mainly focused on the south pole of the Moon. Chang’E-7 (CE-7) mission, through the development of orbiter, lander, rover and hopper, will achieve a comprehensive exploration of the lunar south pole including surrounding, landing, moving, and leaping. The harsh lighting conditions, terrain conditions, and temperature conditions at the lunar south pole have brought many challenges to the design of the spacecraft. CE-7 spacecraft has broken through a series of barriers with advanced technologies including high-precision fixed-point soft landing on complex terrain, lunar surface leaping, lunar landing and walking, global perception and mission planning, and fidelity sampling of water ice and volatiles. It has laid a solid technical foundation for the smooth implementation of the mission and the subsequent aerospace cause in our country.

To deal with the risk of high-risk near-Earth asteroid impacts on Earth，in this article，a detailed mission analysis of impact defense was conducted. Based on this，an “observation + impact + evaluation” asteroid impact defense mission plan was proposed，which solves the problem of existing plans relying on ground-based observation and being difficult to accurately evaluate. Kinetic energy impact and comprehensive and accurate efficiency evaluation can be achieved through a single mission. This paper can provide reference for asteroid exploration missions

In order to meet the autonomous navigation requirements of asteroid approaching impact mission，a method of dim target asteroid recognition based on image registration was proposed. Due to the small size and weak brightness (usually above 10 magnitude) of asteroids, navigation sensors were required to have the ability to image dim targets. This caused the navigation sensor to simultaneously capture a large number of unknown dim stars，posing a challenge to the accurate identification of the target asteroid. The paper utilized the relative motion of asteroids and background stars. Firstly，a combination of ORB feature point localization and BEBLID feature point description was used to register inter-frame images. Secondly，star points were identified based on threshold segmentation，and the structural similarity index between corresponding windows was calculated for each star point. Finally，the detection of dim target asteroids was completed. Compared with the traditional image registration method and target asteroid detection methods，this method has improved speed and accuracy，has overcome the problems of dim target asteroid and unknown background stars，and provides such information as sight vector for optical autonomous navigation of asteroid defense.

When the lunar rover in the future performs complex tasks such as shadowed regions detection and autonomous sampling and return under weak communication conditions in the lunar south pole, the demand for high-precision autonomous navigation system will become more urgent. Taking into account the safety guarantee of the lunar rover and the lunar environmental factors with navigation benefits, a new fusion path planning algorithm for high-precision autonomous navigation was proposed in this paper, by integrating a global auxiliary path based on optimized A* algorithm with Dynamic Window Approach. With location error of simultaneous localization and mapping based on lidar serving as an evaluation index, a numerical simulation and a semi physical experiment were established to verify the feasibility of this algorithm and the effectiveness of improving navigation accuracy of the rover in different application scenarios. Experiment results show that compared with traditional path planning algorithms with single factor considerations, the average absolute location error of simultaneous localization and mapping algorithm in the two-dimensional plane was reduced by a maximum of 42% when the lunar rover moved along the path planned by the proposed algorithm, which can provide technical support for autonomous navigation and path planning tasks in the complex environment of the lunar south pole.

The widespread impact craters and other concave obstacles on the lunar surface are the key factors threatening the safe landing and roving of the lunar rover. Once trapped, it will bring risks of tilt, landslide, and even rollover to the lunar rover. Therefore, the effective recognition and detection of lunar concave obstacles are conductive to obstacle avoidance, and provide necessary information reference for the safe landing and roving of the lunar rover. Based on the concave obstacles’ feature that there is a one-to-one matching between the shadows and the highlights in the sun, an automatic recognition and detection method for the lunar concave obstacles is proposed. The adaptive dual threshold method is used to automatically separate the shadows and the highlights of the concave obstacles from the background. Each shadow and highlight are clustered the specific position and one-to-one matched using the sunlight direction with the prior forecast information involved. Then the rough extraction of every single concave obstacle are obtained. Finally the original sub-images sequence containing every single concave obstacle is traversed for edge detection and ellipse fitting, which can avoid mutual interference of multiple obstacles and effectively detect the locations and ranges of all concave obstacles.

Based on multi-sensor data from star sensors and inertial sensors, a high-performance Kalman filtering algorithm with linearized quaternion measurements was proposed in this paper. According to the ultra-stable and ultra-static platform characteristics of the task, new pseudo-linear measurements were constructed by an approximate transformation for quaternion measurements under small angle change of the spacecraft so that the linear assumption of Kalman filtering was satisfied. Combined with the discrete-time state space model of spacecraft system and the multi-sensor measurements, a Kalman filtering algorithm with linearized quaternion measurements was designed, to achieve high-precision in-orbit state estimation of spacecraft system. The simulation experiments are provided to demonstrate the effectiveness of the proposed Kalman filtering algorithm, which meets the precision requirement of spacecraft attitude estimation for space-based gravitational waves detection and provides the high-precision observation for spacecraft attitude control.

To solve the problem of arm length divergence of space gravitational wave detection formation based on CW equation in two-body nonlinear gravitational field, a formation configuration design method based on second-order CW equation was proposed. Firstly, the differential form of the second-order CW equation was derived, and the approximate analytical solution of the second-order CW equation was obtained by perturbation method. Then, the non-existence of circular flying orbit was proved, and the divergence reason of the nominal configuration based on CW equation was analyzed. Secondly, based on second-order CW equation and the energy matching period condition, the formation configuration optimization model was constructed with the phase angles of the spacecraft as optimization variables, and the multi-constraint configuration optimization method based on the global optimization algorithm and the pattern search algorithm was established. Finally, the optimization results were verified by simulation based on the Taiji mission. Simulation results show that the proposed optimization method can reduce the average error of formation arm length to 0.32% and the maximum error to 0.44 %.

Kinetic impact is considered an effective way to deflect potentially hazardous asteroids from a collision with Earth. To study the effect of impact velocity on the momentum transfer coefficient，6 mm aluminum projectile was used to impact the basalt target at 2-4 km/s. By comparing the computation results of aluminum sphere impact on basalt with the experimental results，the correctness of the calculation and the statistical method of momentum transfer coefficient was verified. The simulation results show that the mass and velocity distributions of projectiles at different impact velocities were almost the same. The greater the impact velocity，the greater the cumulative mass of projectiles. Combing with the experimental and numerical simulation results，the momentum transfer coefficient similarity law of kinetic impacting asteroids was obtained. The momentum enhancement coefficient of the dense asteroid increases with the increased of the impact velocity to the power of 0.65. The momentum transfer similarity law can provide data support for the kinetic impact deflection of asteroids.

The research, technology validation and exercises of planetary defense have become a hot topic and real concern for the international community. General introduction to the international planetary defense exercises (PDE) mainly organized by the United States has been given with a focus on the recent representative 2019 PDE and 2021 PDE. Comparative analysis has been carried out about the exercise participants，scenarios，procedures，and results. Discussions on the related aspects and requirements of planetary defense, such as monitoring and warning，impact risk assessment and active defense strategy， have also been performed. Inspiration and recommendations for Chinese planetary defense actions and related exercises have been proposed.

First, the natural advantages of lunar lava tubes and the research on extraterrestrial farms were summarized. Then key technologies for in-situ resource utilization of the moon were summarized, the basic idea for lunar farm construction in lunar lava tubes was given, and a layout of lunar farm based on lunar lava tube was put forward. Finally, the technical difficulties for lunar farm were discussed. This paper provides new reference for lunar farm construction in lava tube.

To observe the frequency in the range of 0.1 Hz to 5 Hz in lunar-based gravitational-wave detection and improve the sensitivity of gravitational-wave detection, a method of lunar-based gravitational-wave detection was proposed. Based on a brief introduction to the mathematical description and properties of gravitational waves, this paper gave a brief introduction to existing gravitational-wave detectors and compared the lunar-based observatories with the space and Earth-based detectors. Lunar-based detectors that have been proposed, such as Gravitational-wave Lunar Observatories for Cosmology (GLOC), Lunar Gravitational-Wave Antenna (LGWA), etc., are briefly introduced. The critical technique is also discussed and alternative solutions are given. The possible main noise sources and corresponding impact magnitudes for lunar-based gravitational wave detection were discussed. Also, the future development of the lunar-based gravitational wave detection is prospected.

This paper discussed the attitude and drag-free control of two Earth-orbit drag-free satellites with two test masses. The control schemes of the science mode were designed, and a robust controller capable of resisting disturbances was proposed. First of all, based on the science requirements and the LEO characteristics, the configuration scheme for the science mode was designed, to present a stable observation platform for the detection mission. Secondly, decoupling the complex system dynamics model based on characteristics of dynamic coupling and control time-frequency, three loops—the spacecraft attitude control loop, the drag-free control loop and the suspension control loop—were produced. Control requirements for each loop were specified according to mission requirements. Thirdly, taking into account the control requirements in frequency domain and the spectral models of various external disturbances and sensor noises, constrains for sensitivity functions and complementary sensitivity functions of each control loop were derived utilizing the mixed-sensitivity method of H _∞ robust control theory. By selecting appropriate weight functions, an H _∞ robust controller was designed. Finally, simulation results indicate that not only the inter-satellites pointing error but also the pose errors and residual acceleration of test masses satisfy the control index requirements, which verifies the effectiveness of the designed controller.

When the asteroid enters earth’s atmosphere at a very high speed，the surface temperature rises and the surface material melts and loses under the severe aerodynamic heat. Studying the ablation mechanism of iron asteroids entering the Earth’s atmosphere is of great significance to study the ablation mechanism of iron asteroids entering the Earth’s atmosphere to evaluate the impact of such asteroids on the earth. In 2021，the Hypervelocity Aerodynamics Institute of China Aerodynamics Research and Development Center carried out the ablation test of the spherical cone-shaped iron meteorite model（head radius 20 mm，half cone angle 9 degrees）on the arc heater. The tested simulated state is that the stagnation heat flux is 13.9~19.5 MW/m² and the stagnation pressure is 0.51~0.28 MPa. In this paper，based on the experimental phenomenon，the melting ablation model and the melting layer shear ablation model of iron asteroid material ablation are established. and the ablation test state of meteorite model is calculated by using the coupled solution methodology of aerodynamic heat，ablation and internal heat conduction with moving boundary. The calculation and analysis show that the shear ablation model established in this paper can obtain qualitatively consistent stagnation point ablation rate. If the loss of liquid layer is not considered，the calculated law is contrary to the experiment. The calculation shows that the surface evaporation rate is small compared with the mass loss rate of molten layer，which indicates that the ablation of iron asteroids is dominated by the shear loss of molten layer. It can provide reference for asteroid impact Earth defense.

It is crucial to directly confirm the presence of water by detecting water ice and its content in the lunar polar region in situ. Spectroscopy and mass spectrometry are both important tools for identifying and quantifying material composition. They can complement each other to achieve comprehensive detection of water ice, volatile content, and H isotope abundance in the lunar polar region. The paper introduces the spectroscopy and mass spectrometry technique with Luna 25, Luna 27 and Viper as examples of typical in-situ detection applications. It includes the detection mechanism, operating mode and instrument functions, performance and applications. In last, we provided a brief introduction to the upcoming application of the “Chang’e-7” lunar polar region water molecule analyzer. This instrument comprises a laser absorption spectrometer, which is responsible for the in-situ analysis of H₂O and HDO, and a time-of-flight mass spectrometer that enables the analysis of gas molecules with mass numbers < 200 amu, such as H₂O and CH₄. The scheme can support in-situ analysis of water ice for lunar south pole landing missions.

To exploit water ice in-situ resources in lunar polar region, a design method of heat pipe array’s layout was proposed in this paper. Firstly, the heat pipe array was presented according to the water ice mining scheme, and heat conduction process of heat pipe array was numerically solved by three-dimensional finite difference method. Secondly, the objective function of water production and heat flow consumption was established. Genetic algorithm was used to optimize the layout of heat pipe array, and the optimal solution of heat pipe’s layout was acquired by iterative search. Simulation results show that the optimal layout of heat pipe array could obtain maximum water production with minimum heat flow consumption. Besides, mass of water ice collected in a task and total time required were given. The application of this design method to life support system of lunar base can improve the efficiency of polar in-situ resources’ collection.

Formation interferometry near the Sun-Earth libration point is an essential direction for developing high-precision astronomical observation. Keeping the formation configuration stable for a long time is the premise of achieving high-precision measurement. However, the solar radiation pressure will disturb the satellite’s orbit, which challenges the formation configuration’s stability. This paper studies the stable region of formation motion near the libration point under the influence of solar radiation pressure. Based on the Sun-Earth three-body model considering solar radiation pressure, then linearizing the dynamic equation near the reference trajectory of the formation, the analytical expression of the zero relative radial acceleration region near the chief satellite is derived. It is found that the zero relative radial acceleration region is a quadric surface passing through the reference trajectory. The evolution characteristics of zero relative radial acceleration region are further analyzed, and the variation law of region distribution with reference trajectory type, amplitude, and phase is given. Finally, the formation configuration evaluation indexes such as shape, size, and coplanarity are defined. The formation configuration design and control method based on zero relative radial acceleration region is proposed and applied to the design of the five-satellite formation mission. The simulation results show that the formation configuration is bounded within 70 days, and the change rate of the relative distance between the chief satellite and deputy satellite is less than 2% in the first 60 days. In this paper, the study of zero relative radial acceleration region under the influence of solar radiation pressure can provide a basis for designing future Sun-Earth libration point interferometry formation orbits.

In response to the complex joint power supply testing mode, diverse inter spacecraft and ground communication scenarios, and high requirements for simulation flight test design and verification caused by the collaboration, high complexity, high coupling, and high intelligence of Chang’E-7 lunar probe, the difficulties in system level electrical testing were analyzed, and a digital testing and verification strategy for multi vehicle collaboration was proposed. It includes a model based intelligent safety auxiliary testing for multi device joint power supply, a multi scenario high autonomous measurement and control data transmission testing system based on multi-source data autonomous decision-making, and a flight program-simulation flight test design verification system, which changes the current situation where complex system level electrical testing mainly relies on manual or traditional single satellite automated testing technology. It was applied to the development of Chang’E-7 lunar probe, to provide strong support for fully verifying the correctness, consistency, and stability of the functions and electrical performance indicators of the lunar south pole probe, achieve comprehensive, reliable, and efficient testing and verification, and promote spacecraft testing to move further from traditional automated testing of single spacecraft to collaborative intelligent testing of multiple spacecraft.