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.

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.

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.

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.

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.

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.

In situ high-precision analyses of volatile abundance in lunar soil in the lunar polar regions require micro-quantification of test samples. In this paper, a sampling shovel scheme based on the end of a robotic arm was proposed. A shallow lunar soil profile was constructed by progressive shovel digging, micro-quantitative collection of lunar soil samples at fixed depths was achieved through the configuration of a fixed-capacity sampling chamber, and the shovel teeth could be used to scrape the debris formed by the water ice of the lunar soil for sample collection in extreme cases. To verify the feasibility of the sampling scheme, a simulated lunar soil profile shovel-digging sampling efficiency test platform was built, and progressive shovel-digging, fixed-capacity micro-sampling, and vibratory sampling tests were carried out. These tests show that the sampling shovel has the capability of constructing a 130 mm deep profile and a 200 ± 30 mg micro-quantitative sampling function. The research results provide a feasible scheme for the exploration and analysis of China’s lunar soil sampling in the polar regions of the Moon.

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.

China’s deep space exploration has gradually developed from technology and science-driven to the stage dominated by science, leading to technological advances. Under our demand for high-quality development in deep space exploration, the Mega Interconnected Knowledge System in Deep Space Exploration (MIKSE) was innovatively proposed with its concept and scheme conceiving. Centering around the scientific goals, deep space exploration engineering, science, technology, and big data in the application were collected, techniques including artificial intelligence and cloud computing were utilized to perform organic organization, information association, and knowledge mining on relevant elements, a large model with genealogical associations and networks of connections was built, and an intelligent big knowledge platform was established. With the help of this platform, historical data and its current capabilities can be fully utilized to support generative knowledge and information for the future planning and development of deep space exploration and promote the paradigm shift of data-driven deep space research.

The aqueous alteration spectral features of carbonaceous chondrites for were studied for future volatile-rich asteroids exploration and remote sensing. The 1-20 μm infrared spectral features and petrographic characteristics of 15 carbonaceous chondrites with different alteration degrees were analyzed, and the spectral variation laws of the aqueous alteration were summarized. The findings demonstrate that as the degree of alteration of carbonaceous chondrites increases, the 3 μm absorption band, which indicates phyllosilicates and water molecules, and the 6 μm absorption band, which indicates only water molecules, both features increasing in strength and absorption centers shift to the short-wave. With more alteration, the 3 μm absorption band sharpens and resembles serpentine’s 3 μm absorption feature. However, as the degree of alteration increases, the 6 μm absorption band shape does not significantly change. The degree of alteration also affects the spectral shape of the 10-13 μm region. This region indicates silicate features. The 12.4 μm /11.4 μm reflectance ratio reduces as a result of the conversion of anhydrous silicates to phyllosilicates. Also discuss possible effects that the spectra and parameters discovered during this study may have on the outcomes from asteroids.

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.

Soft landing exploration is an important method for exploring extraterrestrial objects, and guidance, navigation and control (GNC) is the key to successful soft landing of extraterrestrial objects. Firstly, the development status of soft-landing missions of foreign and domestic celestial bodies such as Moon, Mars, and small celestial bodies was reviewed. On this basis, the typical GNC schemes for soft landing missions of extraterrestrial objects and the main progress of autonomous navigation and control technology were summarized. Finally, the key technologies for autonomous navigation and control that require special attention and development were proposed for future pinpoint soft-landing missions of extraterrestrial objects, in order to provide the experience and reference for future technological development.

The reflection spectra of satellites are shifted to short wavelengths when seasonal scintillation caused by solar wings occurs, and the shorter wavelength UV band has potential advantages in space target solar wing detection. The space target detection signal-to-noise ratio and detection distance models were developed for space target detection. For the most influential material properties in the model, the spectral reflectance of typical satellite materials and solar wing cell materials in the UV and visible bands were measured, and other influencing factors such as detector and deep space background in the model were also analyzed. Using the SJ-5 and Skynet 5D satellites as examples, it was verified that there was indeed a significant advantage of UV in solar wing detection. The results show that compared with the main body visible detection of the satellite, the solar wing UV detection signal-to-noise ratio is enhanced by 1.3~1.6 times, and the detection distance can be increased by 1.5~1.8 times by the combination of UV and visible light. UV has obvious technical advantages over visible light in detection scenes such as Earth’s limb, occultation and engine tail flame detection during satellite deorbiting, thus UV detection has the obvious advantages of cost-efficiency ratio and detection capability in space target detection.

A lot of dust particles are ejected from the surfaces of the Jovian irregular moons by the impact of interplanetary meteoroids. In this paper, the dynamics of dust particles originating from the irregular satellites in the complicated Jupiter system with various perturbation forces were studied, using both the analytical method and the numerical simulation method. By analyzing the conserved effective Hamiltonian quantity and phase portraits in the orbit-averaged model that describes the long-term evolution of motion of dust, it is concluded that dust particles originating from the prograde satellites tend to be distributed in the direction away from the Sun, while dust particles originating from the retrograde satellite are predominantly distributed in the direction towards the Sun. With long-term numerical simulation, it is found that the orbits of particles originating from prograde satellites are more stable than those of particles originating from retrograde satellites, and the orbital stabilities of large-size dust particles are greater than those of small-size particles.

As solar radiation is an important source of energy received by the surface of the planets in the solar system, accurate modeling of solar radiation on the surface of Ceres is crucial for studying the thermal environment. However, the highly undulating terrain on Ceres makes determining terrain shading coefficients challenging. While the ray tracing method can accurately determine terrain shading coefficients, it is limited by the search radius. In the paper, it examines the effects of seasonal differences, landform types, and study area size on solar radiation simulation, and concludes that a minimum threshold search radius of 74 km is required to determine actual terrain shading. Using this radius, the paper simulates solar radiation over a solar day and finds that the search radius required for accurate shading information varies with time of year and landscape type. Surface faults are most consistently influenced by the search radius, while volcanic landscapes are most significantly influenced. The global solar radiation distribution of Ceres shows a gradual decrease from low to high latitudes. Results improve the theory and method of solar radiation modeling and provide data and theoretical support for future exploration of Ceres.

The Queqiao relay satellite which is located in the Halo orbit at Earth-Moon L2 libration point，needs to maintain its configuration by wheel off loading and orbit maintenance every 3-4 days. According to the orbit characteristics of the libration point，the influence of the component of the orbit determination error for the orbit control parameters is analyzed in the rotating coordinate system，and it is concluded that the orbit determination error affecting the orbit maintenance effect mainly concentrate on the velocity error of X-Y plane. In this paper，an orbit determination accuracy evaluation method for orbit maintenance control is proposed，the strategy of orbit determination is designed，and the influence of different strategies on orbit determination is evaluated. The orbit accuracy of the relay satellite in mission orbit is evaluated，and the results show that it can provide 1-3 mm/s velocity accuracy for orbit maintenance under the existing TT&C conditions.

To overcome the difficulty of absolute optical navigation in unknown environments, an intelligent fusion autonomous navigation method for Mars precise landing was proposed. Considering the difficulties of the inability to detect features and the low efficiency of recognition brought by high texture similarity in the extraterrestrial environment and perspective scaling between images, an unsupervised homography network was constructed to estimate the inter frame motion of the lander. Based on the inertial measurement information, a recursive model of the lander state was established. Using the established measurement model and state recursive model, real-time estimation of the lander position, velocity, and attitude was achieved through UKF. The simulation results verify the effectiveness of the proposed method without the need of feature detection and matching.

Only one vision sensor is incompetent for estimating the motion state of small body. In order to solve this problem, a small body motion state estimation method based on the fusion of camera and LIDAR was proposed. Firstly, a fused camera and LIDAR measurement model was built. By tracking image feature points with depth information, extended Kalman filter was used to estimate the spin angular velocity, spin axis direction, position and velocity of small body. Secondly, a feature fusion matrix was designed to achieve real-time updates of image feature points, point clouds, and fused feature points. Thirdly, the effectiveness of this algorithm and the impact of the number of feature points, observation height, and noise on the algorithm were analyzed. Simulation results show that the accuracy of the proposed algorithm is significantly higher than that of the spin parameter estimation algorithm of small bodies based on monocular camera.

The principle of radio frequency ion thrusters（RIT），as well as the research history and achievements of micro-newton and milli-Newton RIT at home and abroad in the past 60 years，was explained in detail. The radio frequency ion propulsion system involves a number of key technical challenges. Preliminary solutions to the problems of propellant selection， radio frequency（RF）circuit impedance matching，gas flow control，electrical neutralization control and lifetime were proposed， and the development trend and research direction were put forward combined with the future application of RIT.

The stable celestial geological structure，the suitable distance from the Earth to the Moon，and no dense atmosphere and global magnetic field make the Moon a natural and excellent laboratory for the monitoring and research of the Sun-Earth-Moon space weather. This paper reviews the progress of lunar space weather detection and research，and surveys the key scientific problems of lunar space weather and the problems of its prediction application，proposes the concept of the Moon-based space weather monitoring station，set up the specific scientific objectives of the monitoring station，and finally introduces its three major systems and the relationships among them，including the monitoring system，the scientific research system，and the modeling and forecasting system. The establishment of a Moon-based space weather monitoring station is of great scientific significance for studying the mechanism of solar eruptions，the coupling of the Sun to the Earth and the Moon，and the local variations of the Moon’s environment. It will also promote the development of lunar space weather modeling and prediction technologies and improve the capability in providing space environmental safeguard services for future lunar explorations.

To address such the problems as the limitation of the invisible zone of the ground-based monitoring system for near-Earth asteroids and the insufficient discovery and cataloguing capabilities of the monitoring system，a solution of a space-based distant retrograde orbit 4-satellite monitoring system was proposed.Then，the space-based monitoring system's to solve the problems mentioned above was quantified and analyzed，and a cosrreponding model for evaluating the efficiency of the system was set up. A process for the implementation of the corresponding evaluation software was given and an integration of the scoring of various elements was completed in accordance with the visible and infrared spectrum. By analyzing and evaluating，the efficiency of the distant retrograde orbit monitoring layout in compensating for the full-time visibility of the invisible zone of the ground-based monitoring system was verified，as well as the enhancement of the capability of target discovery and cataloguing. This research could provide design reference for subsequent construction of space-based monitoring system.

Mapped Chebyshev pseudospectral convex optimization approach was proposed for Martian ascent trajectory optimization. Firstly, the lossless convexification technique was used to convexify the fuel-optimal problem of Martian ascent. Then, the convexified problem was discretized at mapped Chebyshev-Gauss-Lobatto points and interpolated by the barycentric rational interpolation techniques. Finally, the sequential convex optimization method was used to solve the convex problem iteratively to obtain the numerical optimal solution. Simulation results show that the proposed method is superior to the classical sequential convex optimization method in computational efficiency, and effectively improves the ill-condition of standard Chebyshev differential matrices.

To realize all the six components of terminal position and velocity control for pinpoint landing, throttleable engines are usually needed. In order to reduce economic cost and technique risk, a constant thrust guidance method with yaw maneuver for pinpoint landing was proposed in this paper. The range in the flight line was controlled by yaw maneuver which regulated the in-plane component of the thrust. And a strategy to change the sign of heading angle was performed to eliminate the position and velocity errors in the cross direction, which made the trajectory in horizon plane resemble the letter “W”. This method steered the spacecraft to a given target point with a little more fuel consumption. Simulation results show that the method proposed in this paper is easy to use and efficient.

TheThe process of an asteroid impacting the land is a complex non-linear dynamic process，which is difficult to study by using model tests. Numerical simulation provides an important tool for the analysis of this process. In this study，the large-scale numerical simulation of the dynamic process of the asteroid impacting land was realized initially by using the self-developed software CoSim-DEM based on the discrete element method (DEM). Based on the numerical simulation results，the four stages of the impact process—initial contact，impact excavation, high-speed ejection and adjustment—were simulated；the incidence angle and the dynamic behaviors of the asteroid during the impact process would affect the topographic characteristics of the crater. This study also indicates that large-scale numerical methods can be used to perform the analysis of dynamic process of the asteroid impacting the earth, and provide support for asteroid defense.

The multi-constrained trajectory of minimal fuel consumption was achieved in this paper for the lunar hover hop without lateral thrusters. The hover hop was divided to 3 phases: the vertical rise, the horizontal traverse and the vertical descent. The optimal control of the vertical rise and the vertical descent was bang-bang function. For the first time the control variable of the horizontal traverse was converted from thrust to angle rate, with position, velocity and angle rate considered. The preliminary form of the optimal angle rate for the horizontal traverse was developed by application of the Pontryagin’s minimum principle. With further study on the continuity of the singular point and the number of switching times of the control variable, it was confirmed that the optimal angle rate program consisted of either the maximum or the minimum and there were 2 switchings. A numerical approach to searching the switching points was presented. Simulation results show that the approach with high accuracy and low complexity can potentially be implemented onboard for trajectory optimization.

A hazard avoidance strategy based on augmented curvature guidance was presented for complex planetary surface landing. Based on the basic curvature guidance law, a hazard avoidance augmentation term was introduced. The idea of spacecraft landing space division was used and an anti-collision zone was defined in the collision prone zone near the hazards. The continuous analytical hazard avoidance guidance law was derived based on anti-collision zone. While meeting the geometric convex trajectory state constraints, the hazard avoidance guidance law evaluated the relative position relationship between spacecraft and hazards, which can quickly steer the spacecraft away from hazards and increase landing safety. Simulation results reveal that the validity of avoiding terrain hazards on the complex planet surface and achieving pinpoint soft landing is enhanced, with good flexibility and reliability.

Lava tubes are one of the prime candidates for establishing extraterrestrial bases. To verify the feasibility of using ground-penetrating radar to detect lava tubes on extraterrestrial bodies, this paper first conducted a technical study to validate the detection of lava tubes using a 400 MHz ground-penetrating radar system on the Seventy-Two Caves and Wolong Cave in the Shishan Volcanic Group in Haikou, Hainan. It is found that the upper interface of the lava tube is clearly displayed when the depth of the tube is 2 m, and the radar image shows the upper and lower boundaries when the height is less than 3 meters. Additionally, the genetic algorithm is employed to inverse the dielectric constant of the lava tube’s wall. The reliability of the genetic algorithm in calculating the dielectric constant is validated through comparison with results obtained from the depth method and sample measurement. Furthermore, the analysis of samples establishes a simple relationship between porosity and dielectric constant. These findings are of significant importance for assessing the underground spatial distribution and wall stability of the lava tubes, providing a reference for future lunar base establishment.

An adaptive iterative guidance strategy was designed for the guidance of Mars ascent vehicle in the orbiting phase. To reduce the effects of initial state deviation and the uncertainty of the Martian environment, the remaining flight time was calculated iteratively in the guidance coordinate system in each cycle, and the optimal control angle satisfying the constraints of the target point position and velocity vector was solved under the fixed thrust of the ascender, so as to correct the flight trajectory in real time. The simulation results show that compared with the traditional open-loop guidance scheme, the proposed scheme significantly improves guidance accuracy, in which the altitude error is reduced by three orders of magnitude, the maximum velocity error is reduced to one-third of that of the original open-loop guidance, the orbital inclination and eccentricity errors at the entry point satisfy the basic engineering requirements, and it can be used as a reliable scheme for the future guidance of the Mars ascent vehicle in the orbiting phase.

During the attachment process of small body spacecraft, there are scale, viewpoint and illumination variations in the image, making it difficult for traditional feature-matching algorithms to obtain accurate matches. In this paper, a small-body cross-scale illumination invariant matching algorithm is proposed. To address the problem of scale changes in the image during the attachment process, the global attention mechanism is combined with the dilated convolution to construct a scale adaptive adjustment module; the viewpoint invariant feature extraction module is designed to solve the problem of low matching accuracy under the large viewpoint changes in the feature matching algorithm; the self-attention mechanism is combined with the inter-attention mechanism to establish the feature dependency relationship, and the illumination invariant features are extracted. Experimental validation is carried out using the real images of Ceres and Bennu, and the results show that the proposed algorithm achieves an accuracy of more than 89% under large scale, view angle and illumination changes.

To meet the demand for long-life carbon nanotube field emission cathode in deep space exploration，the failure mechanism of CNTs cathode was investigated，and a long-life CNTs cathode design was introduced. Patterning the CNTs as an array of CNTs island offers a way to eliminate the shielding effects of electrical field. In this way the areas of emitting CNTs are larger，which avoids over-heating on a small emission area. A bonding technique was introduced，the contact between CNTs and substrate was maintained by molecular forces previously，melting metal was introduced as the bonding layer. The mechanical robustness of the CNTs cathode was enhanced while the electrical/thermal resistance was reduced. Performance tests were conducted on the prototype in a high vacuum environment. The prototype produced a current of 0–1 mA with a resolution less than 2 μA and the noise level was less than 1 μA/Hz^1/2@0.01–1 Hz. The prototype was tested by over 550 hours' continuous emitting，showing good stability in long-term use.