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We design and complete an experiment of debris detection under the Milky Way background. The data analysis shows that the strong Milky Way background reduces the detector's ability to detect the weak debris, but has little effect on the accuracy of the astronomical positioning of debris. This paper verifies the rationality of using the limit detection magnitude method based on the detection probability to characterize the limit detection ability of detectors. It also verifies the feasibility of using the simulation method to increase the data completeness. The work in this paper will provide a basis for the design of the spacebased detectors and the development of the detection experiments. [ABSTRACT FROM AUTHOR]

A kind of data-driven responsive test technique is presented in this paper. The data are sampled by using the on-board system based on built in test (BIT) technique, and sent to a ground system through high speed data bus； the evaluation procedure as the playback of the on-board processing is triggered by using these data with the same model and algorithm in the ground data processing terminal. The calculation results of the on-board system and the ground system are compared to detect and isolate failures quickly. Both background and necessity of the technique are reviewed, and a rather comprehensive introduction is provided for the implementation of each part of the design including selection of the monitoring spot, bus interception technique and data management task. Moreover, the principle of data evaluation for various representative signals and the means for fault detectectionand isolation are illustrated. The analysis is real-time, automatically, and can adapt the test cases adjustment, which is beneficial to system-level test coverage, thus decreasing test equipment, time for data analysis and engineers involved in technical support. [ABSTRACT FROM AUTHOR]

Aiming at solving the problem of the large solution space and mixed decision variables on agile image satellites scheduling, a scheduling model with multi-decision variables is built, and an improved quantum genetic algorithm is proposed in this paper. The improved algorithm adopts a hybrid coding strategy, which combines the binary with the real number coding. The hybrid coding is more concise compared to the classic coding of the satellite scheduling. Based on the hybrid coding strategy, the observation functions are designed to map the solution space of the agile image satellites to the quantum space so that the agile image satellites scheduling problem could be solved effectively with the quantum optimization mechanism. In the end of this paper, the simulations in different sizes are performed to verify the proposed algorithm. The simulation results show that compared with the classic algorithms, the improved quantum genetic algorithm proposed in this paper has better performance in both quality and time efficiency. [ABSTRACT FROM AUTHOR]

This paper analyzes the electromagnetic pulse (EMP) environment of a launch vehicle in the air, and builds a model of EMP disturbing the sensitive equipment, including the conducted electromagnetic interference and the radiated electromagnetic interference. In order to solve the restriction of the take-off mass to the overall parameter design, the paper employs the simulated annealing (SA) method to solve the problem of the typical system’s EMP protection, taking the minimum take-off mass as the objective function. The model proposed in this paper provides a balance selected strategy between the EMP protection and the additional mass. The simulation results show that the typical system meets the EMP protection index during the flight and achieves the minimum additional mass after optimization. [ABSTRACT FROM AUTHOR]

When a satellite uses stellar refraction to conduct navigation，it often occurs that the navigation refraction stars can' t be observed because of the influence of the celestial bodies such as the Earth, Sun and Moon. Thus the accuracy of locating will decrease a lot. Moveover, the filtering of navigation can be diverging. This paper proposes a new method based on neural network compensating navigation data in the blank section of starlight. The method utilizes the related properties between the correlation of the navigation errors and status errors. It establishes three layers of the neural network system，which could effectively predict and correct the information of the satellite status and could ensure that the navigating errors change smoothly around the starlight blank section. Then the high-precision navigation for satellite can be achieved. This paper constructs the influence models of the celestial bodies and describes the mechanism about how the blank section of starlight occurs and the scheme of designing the neural network system. Finally, the efficiency and high accuracy of compensating the blank section method is verified via simulation. [ABSTRACT FROM AUTHOR]

An improved in-orbit pointing error calibration method of laser communications terminal (LCT) is proposed in this paper based on the developed pointing error model and in-orbit data acquisition method. Several pointing error factors are introduced in the model to solve the problem of the incomprehensive modeling of error factors. The excitation signal in the link-observation method excites the pointing error insufficiently due to the limited amplitude. This paper introduces the light signal received during the link acquisition phase while the pointing mechanism is swinging actively as the excitation signal, and further optimizes the signal to maximize the degree of the observability. The simulation results show that a significantly improved pointing accuracy of the laser communications terminal is achieved, with the maximal pointing error (azimuth direction) reduced from 867.8 μrad to 112.1 μrad and the maximal pointing error (elevation direction) reduced from 62.1 μrad to 51.5 μrad. [ABSTRACT FROM AUTHOR]

This paper studies the impact fluxes calculation for the orbiting space objects via the Chan's model which does not invoke either the kinetic theory of gases model or the Poisson distribution function. Four cases are discussed for the space objects on elliptical orbits passing through a thin spherical shell surrounding the spacecraft. The paper also compares the circular orbit assumption with the elliptical assumption. The satellite Iridium 86 is used to estimate the impact fluxes under both assumptions. It shows that the ratio of the impact flux between the elliptical orbits case and the circular case decreases from about 4 times to 1. 4 times as the thickness increases. The statistical number of the objects gets a big fluctuation as the increased thickness in circular case. The elliptical case is 60 times more than the circular case when the shell' s thickness equals to 5 km. [ABSTRACT FROM AUTHOR]

A final phase attack area modeling method of a kinetic kill vehicle (KKV) and an optimal evasive strategy of a target is proposed in this paper to analyze the opposed process between KKV and the high speed target. Firstly, based on the analysis of the space geometry, the projection of the maneuvering range of both KKV and target in the attack area is calculated. Based on the established model, the calculating methods of the capture region, escape region and barrier are derived and the explicit formulation is obtained. Then, the fuel consumption is introduced as a condition of the energy constraint. Thus, the attack area calculating model is established with the energy constraint. According to the attack area model, the optimal evasive strategy is obtained through the analysis of the attack area and projection calculation. Finally, the simulation results show the effectiveness of the model, projection calculation and optimal evasive strategy. Using the proposed model, the capture and escape region can be calculated in a convenient way. With the analysis of the attack area in different cases, the model proposed in this paper can offer convenience for research on the conditions of the association of the booster and KKV. [ABSTRACT FROM AUTHOR]

A method for designing accurate autonomous navigation system is proposed in this paper for automated transfer vehicles (ATV). This paper devises an accuracy enhancement approach for traditional integrated navigation of a strapdown inertial navigation system (SINS) and a celestial navigation system (CNS) with the virtual observations. This approach benefits from the use of the fact that ATV is in complete weightlessness in orbit without maneuvers. The improved state equations and virtual observation equations are established based on such a constraint, and an extended Kalman filter is used to accomplish the state estimation from SINS, CNS and virtual observations in different data rates. The simulation results indicate that the proposed algorithm can improve both the position and velocity accuracies without loss of attitude estimation accuracy by about 82.33% and 93. 87% compared with standalone inertial navigation, by about 98. 35% and 98. 72% compared with traditional SINS/CNS integration. The introduction of virtual observations can resist the divergence of position and velocity errors due to inaccurate accelerometer bias estimation effectively. This is of significant importance in engineering because the navigation accuracy is improved without the aid of other sensors, meaning it reduces the reliance on the external information for SINS. [ABSTRACT FROM AUTHOR]

An optimization method of trajectory design is established in this paper for manned lunar landing circumlunar free-return flight mission. The problem of designing free-return trajectory with multiple constrains under the high precise dynamic model is converted to the nonlinear bounded optimization problems. A solving strategy consisting of hybrid and two-level optimization algorithm is then proposed. Under the double two-body model, the initial trajectory with the weak constrain conditions is obtained by hybrid optimization algorithm which consists of differential evolution (DE) method and sequence quadratic program (SQP) method based on the patched-conic approach. Then a two-level initial trajectory corrective measure based on the sequence quadratic program is applied to obtain the final solution satisfying the strong engineering constrains under the high precise dynamic model. Finally, the reliability and effectiveness of the approach proposed in this paper are demonstrated by the simulation tests, and the results indicate that the proposed method has excellent convergence performance and high precision, thus can be a useful tool for manned lunar orbit design. [ABSTRACT FROM AUTHOR]

This paper presents a novel coupling characterization based robust control scheme for hypersonic vehicles. First of all, the attitude equations of a hypersonic vehicle are denoted, and the error dynamic model of the hypersonic vehicle is obtained based on the backstepping technique. Then, a robust coupling-based control scheme is proposed combining with the disturbance observer, and the asymptotic convergence is guaranteed through the sliding mode compensation. Finally, the integral absolute error (IAE) performance index is introduced, and the better performance of the proposed method is proven theoretically. The proposed method not only guarantees the asymptotic stability and the strong robustness, but also improves the dynamic performance via considering the coupling characterization into the controller design. The aerodynamic parameters perturbation and actual actuator constraints are considered in the numerical simulations, and the results demonstrate the validity of the control method in this paper. [ABSTRACT FROM AUTHOR]

Based on drag acceleration profile, a predictor-corrector guidance law which can guide longitudinal motion and lateral motion synergistically is proposed in this paper. The drag acceleration profile is designed through interpolating between upper drag boundary and lower drag boundary, and then corrected to eliminate the range error. The altitude error is eliminated by adjusting attack angle. The lateral error is eliminated by regulating the reversal time of bank angle. Comparing with the traditional methods, the proposed one can correct the 3-dimensional motion of the vehicle. Using interpolated drag acceleration profile, the flight constraints can be easily dealt with. Moreover, in a correction cycle, the method in this paper only needs twice trajectory predictions, which is favorable for on-board calculation. The simulation results indicate that the proposed guidance law has a high precision and robustness. [ABSTRACT FROM AUTHOR]

For launch vehicles with constant thrust and without auxiliary propulsion systemCa direct method on simultaneous framework (simultaneous method) is presented to solve the dynamic online trajectory planning problem with large terminal attitude constraintCmaking up for the deficiency of linear programming in the traditional iterative guidance method, meanwhile, the angular rate of the trajectory can be limited according to the requirement of the attitude tracking error, so as to satisfy all constraint conditions. By combing the characteristics of the direct collocation method and pseudo-spectral method, and based on orthogonal collocation on finite element, this paper adopts the simultaneous method and discretized state variables and control variables to solve this problemCwhich is much more efficient than the pseudo-spectral method. On this basisCthe paper puts forward some measures to increase the calculation efficiency, such as initial value selection, orbit precision error adjustment, and adaptive finite element configurationCfurther improving the real-time performance and providing feasible solutions to more complex and diverse guidance tasks in the future. [ABSTRACT FROM AUTHOR]

The thermodynamic parameter fluctuation of plasma sheath could change the transmission and reflection coefficients. This paper deduces the relation between the thermodynamic parameter fluctuation of plasma sheath and the transmission and reflection coefficients. On this basis, the changes of the transmission and reflection coefficients at S and Ka bands are simulated. The results show that，when the electron density increases, the change of the reflection coefficient decreases and the change of the transmission coefficient increases, at S band. At Ka band, when the collision frequency is 10 MHz, the change of the reflection coefficient increases and the change of the transmission coefficient decreases； while when the collision frequency is 1 GHz and 50 GHz，the change of the reflection coefficient increases and the change of the transmission coefficient increases first and decreases later. Besides, the effects vary with the altitudes. The changes decrease first and increase later at S band. At Ka band, the change of the transmission coefficient decreases first and increases later, while the change of the reflection coefficient experiences a decrease-increase-decrease tendency. The effects are different in diverse plasma situations. Thus it is proposed that the TT & C system should be well-designed aiming at specific plasma environment. [ABSTRACT FROM AUTHOR]

The libration point rendezvous and docking with a non-cooperative target is investigated based on the high-order integral-chain differentiator and the prescribed performance control theory. Just knowing the relative position states, this paper proposes a new control law for spacecraft rendezvous during the terminal phase. Firstly, the high-order integral chain differentiator is used to estimate the relative velocity states of the two spacecraft, and a mode-free prescribed performance controller is designed, which makes the relative motion states of the two spacecraft asymptotically converge to the desired state within the prescribed boundaries. Then the Lyapunov function is used to prove the stability of the system when there are disturbances in the relative motion states. This method is of closed-loop control and independent of the model parameters, thus it is easy to be employed online. The simulation results show that even though there exist uncertainties such as the unknown disturbances and navigation and guidance errors, the proposed control law can achieve high-precision, real-time control of the spacecraft when tracking the non-cooperative target, and shows strong robustness. [ABSTRACT FROM AUTHOR]

The flexibility optimal design and dynamic analysis for the drawout-expanded ramps are carried out in this paper. Firstly, the geometrical principle of extrusion between a rover and ramps with different angles is analyzed. Then, the clearance mechanisms and limit mechanisms of the ramps are designed, and the optimal values of the key design parameters of the mechanisms are calculated, so as to adjust the distance between the two ramps adaptively and reduce the force between the rover and the ramp guardrails. Finally, the process of the ramps descent and the rover driving on the ramps are simulated to verify the effect of the flexibility optimal design for the ramps. The results show that the flexibility of the optimized ramps are greatly improved, and the distance between the two sides of the ramps can be adjusted adaptively. Using the optimized ramps can effectively reduce the force between the rover and the ramp guardrails, and realize the safe operation of the rover on the ramps. [ABSTRACT FROM AUTHOR]

To investigate the dynamics and the potential of the control mechanism of a fixed-trim re-entry vehicle with a moving-mass roll control system and provide the theoretical references for engineering practices, the 7 -DOF dynamic model is generated in this paper. Then, the kinetic characteristics and the dynamic coupling between the moving mass and the carrier are studied with the frequency domain analysis to reveal the control m echanism of the flight vehicle control system. M eanw hile, according to the analysis results of the coupling between three channels and the im pact of the actuator param eters on the control au thority, some suggestions on the structure and control system design have been made in this p ap er, which provide the theoretical references for a flight vehicle with a moving-mass roll control system in engineering practices. [ABSTRACT FROM AUTHOR]

The catalyzer of the HAN-based thruster is prone to breakage in the long-time working conditions. A new design method of the thruster with a spring bed structure is proposed in this paper, which optimizes the structure of the thruster catalytic bed. The elastic force provided by the spring in the high tem perature environment is sufficient to resist the flow friction generated by the catalytic bed. M eanw hile, the minimum elastic force is sufficient to overcome the flow resistance of the catalytic bed. All these advantages improve the longevity and reliability of the thruster. In order to verify the validity of the proposed design m ethod, the hot-starting tests of both the traditional structure and the new spring bed structure designed for the IN HAN thruster are carried out. The results demonstrate that the hot-starting times of the IN thm ster with the new spring bed structure exceed 500, compared to less than 150 cycles of IN thruster with the traditional structure. The studies provide a prospect foundation for the design of the HA N-based thruster. [ABSTRACT FROM AUTHOR]

In this paper, based on the special conditions of a space radiator, the heat transfer model is established. It is proved that the model and the calculation method are feasible by comparing with the actual designing process. With the fin length and fin thickness and other parameters selected as the variables, the heat dissipation of the fin in the heat pipe radiator and the quality characteristics of the system are analyzed and optimized, and finally the optimal design is found which has potentials in thermal design and analysis. [ABSTRACT FROM AUTHOR]

This paper designs a new type of ITPS containing phase change material layer (PCM-ITPS). The numerical simulation is conducted to discuss the impact of the PCM on the thermal protection performance, and the PCM-ITPS unit cell test samples are manufactured to test the thermal protection performance. Both numerical simulation and test results prove the excellent thermal protection performance of the PCM-ITPS. On this basis, the thermal stress finite element simulation of the model is completed to verify its mechanical performance. Furthermore, the platform for the automatic design and optimization is built for the PCM-ITPS. With the structural dimensional parameters as the design parameters and the performance requirements as the constraints, the lightweight design of the integrated thermal structure is accomplished. As a result, the mass of the optimized PCM-ITPS is reduced by 23.35% compared with the optimized traditional ITPS. In conclusion, this work is able to provide the theoretical and technical support for the integrated design and manufacturing processes of a thermal protection system. [ABSTRACT FROM AUTHOR]

For a new kind of dual-spin spacecraft mission which is used for earth-observation, a method to manage the rotor's angular momentum with magnetic torquers is introduced in this paper. Three magnetic torquers fixed on the rotor part produce periodic magnetic momentum which contracts with Earth's magnetic field, balancing the angular momentum caused by friction of bearing while no angular momentum accumulation is caused to the other two axes. This method is applicable in engineering. Simulation shows that the total angular momentum of rotor converges to the desired value and does not accumulate over time. [ABSTRACT FROM AUTHOR]

The system integration technology and architecture of the distributed integrated modular avionics (DIMA) for the next-generation launch vehicle is introduced in this paper. According to the system integration route, a lot of theses are discussed, including the goals of the system designation, system functional requirement analysis, system abstractions, system synthesis technology and so on. Firstly, the system requirement analysis in accordance with the avionics functions. In this step, two system abstraction technologies, functional abstraction and layered abstraction, are used to define the abstract system model and the high coherent, low coupling atomic function modules are extracted as a result, at the same time, the attributes, interactions and sequence constraints of these modules need to be defined. And then, the system visual presentation technology is mentioned and used to carry the deep system analysis out. In the next system synthesis process the function modules above can be mapped to the hardware resources, and the integrated control unit and its boards are presented accordingly, At last, the planning of the nodes and partitions, the blue print of the failure tolerance architecture based on the time and space partition technology (TSP) is defined, and the scheduling model of the TSP operating system and switched data interaction network is discussed as well, thus the software and hardware architecture is clear finally. [ABSTRACT FROM AUTHOR]

The L-band navigation signals are easily affected by the intentional or unintentional interference and spoofing, which may lead to the regional performance degradation or even failure of the navigation system. This paper presents a new navigation approach for the terrestrial users based on Beidou Ka inter-satellite links. Firstly, the feasibility of the approach is ascertained and the measurement model under time division system is given; Then, an epoch reduction method for the Ka measurements is proposed using the receiver clock model and the measurements from the inertial navigation system, based on which the Beidou Ka inter-satellite link based real time navigation algorithm for the terrestrial users is derived; Finally, the influence of different factors on the performance of the algorithm is analyzed by the numerical simulations. The simulation results show that the proposed algorithm can achieve a satisfactory position precision within 2.0 meters, which can compensate for the lack of the regional failure of the L-band navigation signals to a certain extent. [ABSTRACT FROM AUTHOR]

Taking the risk identification and control technology of Tiangong space lab No. 1 as a traction, this paper puts forward some suggestions on the phased application of risk identification and control methods. In view of the important risks and the characteristics of space lab assemblies, the relative risk identification method and the downgraded reconstruction risk control method are proposed to identify the major risks of space laboratories from the perspective of relative risks. When Tiangong 1 is unable to control the a ssemb lies, manned spacecraft is used to replace Tiangong 1 to control the space lab assemblies. It avoids the problem that the risk identification results fluctuate too much, and reduces the system risk without increasing equipment redundancy and other sections. [ABSTRACT FROM AUTHOR]

In order to develop an intelligent guidance and control system, which can increase the mission robust performance in the full launch cycle, this paper provides the launch vehicle fault modes, and presents a fault classification method based on the energy characteristics firstly. The function and performance requirements to the guidance and control system are put forward for different ranks of energy fault. Especially, for the small and medium energy faults, the self-adaptive guidance methods, including the case and orbit-changing principle, are introduced; besides, the ways of implementation for the applications of the self-adaptive guidance technology are discussed. The fault classification method based on the energy characteristics and the self-adaptive guidance method can be applied to the future launch vehicles of China. [ABSTRACT FROM AUTHOR]

In order to optimize the layout of the spacecraft thermal control fluid loop with multiple radiators, improve the heat dissipation efficiency of the fluid loop, and reduce the fluid loop temperature, based on entranspy dissipation theory, this paper analyzes the heat-dissipation process of the fluid loop layout in series and in parallel with multiple radiators. The results show that when the same amount of heat is dissipated, the uniformity of the temperature difference between the fluid and the wall of the pipeline is better, and the smaller the entranspy dissipation of the heat dissipation process of the fluid loop is, the better the cooling process of the system is. Further, for the case of two radiators, the radiators are respectively provided with different space heat fluxes, and the radiators are compared with different fluid loop layout patterns. The results show that when the radiators are connected in series with the fluid loop, the heat dissipation performance of the system is better than the parallel connection of the radiators and the fluid loop. At the same time the fluid temperature level of the system is the lowest. The result is completely consistent with the prediction of the entranspy theory. The conclusion of the study has guiding significance for the design of the spacecraft thermal control fluid loop with multiple radiators. [ABSTRACT FROM AUTHOR]

The numerical simulation method and the transport of the communication characteristics for different electromagnetic waves of the plasma sheath are analyzed. Firstly, based on the flight communication data of a blunt-nosed project, the numerical simulation method and the transport method of the communication characteristics in this paper are preliminarily proved to be feasible. Secondly, the communication characteristics of the plasma sheath for the lifting reentry vehicle are obtained in the typical trajectory. The transport of the communication characteristics for the S-band signals, Ka-band signals and K-band signals are also investigated, which indicates that the high-frequency signals will improve the communication characteristics and can be an effective technical approach for solving the communication blackout based on the domestic relay method. Finally, the influences on the transport of the communication characteristics of the direction angle and the angle of attack are investigated. The results can provide a reference for the communication design of the reentry vehicles to solve the communication blackout in China. [ABSTRACT FROM AUTHOR]

A method for designing a switched controller based on a fuzzy logic system is proposed in this paper for a class of the variable-sweepback-angle near space vehicles (NSV) affected by the external disturbances and parameter uncertainties under the tracking performance and angular rate constraints. The nonlinear switching model of the vehicles containing the unknown disturbances and uncertainties is established. By designing a fuzzy logic system, all the unknown nonlinearities can be real-time estimated. Based on the back-stepping method, a switched controller is designed and the "total disturbances" are compensated in the controller. By means of the common Barrier Lyapunov function theory, it is proved that the proposed control strategy can guarantee the stability of the close-loop switching system and the tracking performance and state constraints are not violated. The numerical examples show the effectiveness and advantages of the proposed method [ABSTRACT FROM AUTHOR]

With the development of the load and maneuver capabilities of modern satellites, along with the increase of the diversification and complication of satellite observation tasks, the autonomy level becomes the key technique which seriously influences the scheduling efficiency for agile Earth observation satellites. This paper illustrates the characteristics and normal description of the agile observation satellite scheduling problem. Then in terms of the autonomous perception, decision and cooperation, the research progress in key techniques during the autonomous scheduling for agile Earth abservation satellites are separately reviewed. Finally, considering the future application requirements on satellite technologies, several suggestions on further development of the autonomous scheduling technology are proposed. [ABSTRACT FROM AUTHOR]

In order to evaluate the spatial signal quality before and after the conversion of the GPS LI frequency point signal system, this paper compares the quality of the coherent adaptive subcarrier modulation (CASM) modulation and the QPSK modulation based on the data collected by the high-gain antenna receiving system. Firstly, the CASM modulation model is briefly introduced, and the waveform matching technique is used to solve the pseudo-code sequence of the LI frequency authorized signal. Secondly, the power allocation problems of QPSK and CASM modulated signal components are solved respectively based on the constellation distribution and the maximum likelihood estimation. Finally, the S-curve bias (SCB) and the correlation loss (CL) in the relevant characteristic parameters are used to quantitatively analyze the spatial signal quality of each signal component before and after the conversion of the LI signal system. The results can provide references for the comparison of the spatial signal quality assessment under the different signal systems. [ABSTRACT FROM AUTHOR]

A method of SINS initial alignment under the condition of no latitude based on calculation of Earth axis vector is proposed. The solution in this paper relies on the detection of the vector of the Earth rotational angular velocity which is called as the Earth axis vector on reference frame to define the navigation frame (n-frame) relative to the reference frame which is the board frame (b-frame) or board inertial frame (bO-frame). When the SINS under the static base, the orthonormal attitude matrix can be determined by building the orthonormal projection of the n-frame axis on the b-frame which is derived from the measurement of the Earth rotational angular velocity and the gravitational acceleration using gyroscopes and accelerators. On sway base, firstly, after building two sequences of the equivalent angle rotation around the Earth axis vector according to the measurement of gravity vector, then the Earth axis vector can be calculated using the solution of the QUEST algorithm. Thus, the bO-frame orthonormal projection of the n-frame axis can be obtained. Lastly, the relationship of the b-frame and n-frame can be determined according to the change of the b-frame relative to the bOframe using the gyroscope data. The calculation test of the static base shows that the precision of the alignment method proposed is equivalent to the traditional method with the efficiency being improved. The sway-base simulation and shipborne test show that the calculation precision based on the QUEST algorithm is superior to the method based on the geometry of three vectors, and then the precision can be further improved with the application of the low-pass filter algorithm. [ABSTRACT FROM AUTHOR]

The method for medium-and long-term atmosphere density retrieving is studied. Based on the orbit data of China's typical remote sensing satellite, the MSIS00 atmospheric model is modified using the atmosphere density retrieving result with the measured data, then the modified model is used for the propellant budget of the remote sensing satellite. The simulation results show that the modified atmospheric model obtained has a high accuracy, and compared with the MSIS00 model, the fuel consumption for orbital maintenance with the modified model is reduced by 3 5 % . It can achieve the maximum mass reduction of the satellite and also ensure the safety of the satellite. The result of this paper can also be used in high precision orbit prediction, propellant budget and collision avoidance. [ABSTRACT FROM AUTHOR]

A surround space solar power station (SSPS) power topology with the hierarchical power design method is proposed. The topology is suitable for the SSPS with multi-rotary joints. The unified power management technology for the power balance control system is put forward in the paper. The maximum power point tracking ( MPPT) control, MPPT control plus stable DC bus voltage control, and MPPT algorithm plus stable DC bus voltage drop control methods are simulated. The simulation results show that the drop control strategy based on virtual impedance is better. [ABSTRACT FROM AUTHOR]

The hexapod mobile robot, which can bear the heavy load and traverse in the unknown environment of the lunar surface, is a necessary device for lunar exploration. Although the hexapod robot walking over a rugged terrain can be accomplished by employing the ground contact and attitude information, and can make a reflex action when encountering the small obstacles, however, the obstacle avoidance based on visual information is an important issue in the field of the legged locomotion when faced with the insurmountable obstacles. For an electrically-driven and radially-symmetrical hexapod robot, the terrain modeling for the lunar surface is based on the information from the laser range finder. In this paper, a virtual trunk body model is presented to achieve the autonomous obstacle avoidance strategy in the unknown environment, and the real-time optimal feasible directions and minimum distance are acquired to avoid the obstacles. The path trajectory of the trunk body and foot trajectories are planned to walk toward the feasible direction. The experimental result shows that the hexapod robot can track the yaw angle and in real time accurately from the obstacle avoidance method to achieve the obstacle avoidance autonomously in the unknown environment. The key techniques will lay a foundation for the research of the heavy-duty multi-legged robots for lunar exploration. [ABSTRACT FROM AUTHOR]

In order to improve the autonomous operation ability of a bias momentum microsatellite, a sliding mode fault-tolerant control method based on an observer of uncertain terms is proposed. Using the disturbance observation method of the Euler-Lagrange system, an observer of uncertain terms is designed to estimate the actuator faults, such as the reduction of the momentum wheel output torque and the resistance drift of the magnetic torquer' s coil as well as the environmental disturbance torques of the satellite, and the theoretical deduction shows that the observation error of the observer is uniformly ultimately bounded ( UUB). The estimated values of the observer are used for the feedback compensation of the sliding mode fault-tolerant controller. The stability analysis shows that the proposed method can quickly converge the satellite attitude to the sliding surface. It is noted that the control method proposed in this paper does not need to make the small-angle assumption and the fault-tolerant control process is not dependent on the working state information of the actuators. The attitude control performance is evaluated by the numerical simulations. [ABSTRACT FROM AUTHOR]

A bistatic radar system combined with the Tianlai radio telescope array and an incoherent scattering radar, which is assumed as a source of transmission in Qujing, Yunnan Province, is proposed to detect the space debris. The detection performance of the system, including the radar cross section (RCS), the detection time and the detection efficiency of the Tianlai radio telescope array is calculated and analyzed in the paper. The analysis shows that the system has the potential ability to detect small space debris whose diameter is less than 10 cm, and then provides the methods of determining the cross beams and positioning space debris based on this system. [ABSTRACT FROM AUTHOR]

Space autonomous rendezvous to a non-cooperative target is a key technology of an on-orbit operation mission or space attack and defense mission. Maneuvers of a non-cooperative target spacecraft brings many difficulties, such as avoiding, spin and nutation. A standard convex programming problem for the autonomous rendezvous based on a certain propulsion system under some necessary constraints is formulated in this paper. Then, the guidance errors which are caused by the non-cooperative target’s dynamic characteristics and elimination technique are analyzed. An advanced guidance method is proposed. The primal-dual interior point method is the core optimal algorithm of this method. Finally, several explicit simulations are carried out to confirm the feasibility and robustness of the present algorithm. [ABSTRACT FROM AUTHOR]

In this paper, a modified quasi-consistent cubature Kalman filter (MCKF) based on relative position measurements in a dual-satellite system is proposed for the autonomous navigation of a distributed satellite system (DSS). The only difference between the MCKF and the standard cubature Kalman filter (CKF) is that in MCKF the error covariance matrix from the observability theory of a nonlinear system is adjusted on line. The numerical simulations show that the MCKF is quasi-consistent and less sensitive to the observable degree than the usual one. Moreover, it indicats that the MCKF can shorten the stabilizing time of the systems with high accuracy. [ABSTRACT FROM AUTHOR]

For inhibiting the joint load compensation torque jump caused by an unexpected joint failure when space manipulator executes the load carrying tasks, the optimization model and its solving process are proposed in this paper. The load compensation torque jump caused by the locked-joint failure is analyzed at first, and to minimize the torque jump at failure moment, the optimization model of the joint load compensation torque jump in the presence of the unexpected joint failure is established. The correction item of the joint torque containing the compensation coefficient and statics manipulability gradient is constructed and the optimal inhibition of the joint load compensation torque jump can be realized by fitting the optimal compensation coefficient function. Finally, the effectiveness of the proposed inhibition method is verified by the numerical simulation. The results show that the joint load compensation torque jump caused by the unexpected joint failure can be effectively inhibited by the proposed method, and the average inhibition ratio can reach up to 89.26%. Meanwhile, the accuracy of the operating force on the end-effector will not be affected, thus the space manipulator can finish the load carrying tasks stably and safely. [ABSTRACT FROM AUTHOR]

The visual based planetary rover autonomous terrain perception, navigation, path planning and control system is an important safeguard for the safe and efficient scientific detection. This paper summarizes the navigation and control systems of the planetary rovers that have been successfully launched or programmed in the future. We focus on combing the progress of several key issues such as multi-source terrain perception, autonomous global or local navigation, autonomous path planning and control. Combining the future mission requirements, the autonomous and intelligent development trend is summarized and prospected, and a research framework for the visual navigation and autonomous control of the planetary rovers is constructed. [ABSTRACT FROM AUTHOR]

As to the problem that traditional space manipulation devices are hardly applicable to the on-orbit construction of big scale space facilities, the space cellular robotic system (SCRS) which can realize the multilevel self-configuration is proposed in the paper. Its conception system and design philosophy are presented. Hardware designing of SCRS in the scenario of on-orbit assembly of space triangular truss structure is introduced. The key techniques including the multi-agent cooperative automatic planning under uncertainty, configuration decision of multi-layer robotic system, multi-agent cooperative autonomous unmapped navigation, and multi-agent hierarchical cooperative distributed control are summarized. Finally, the application prospect of the SCRS is proposed according to its features and advantages. [ABSTRACT FROM AUTHOR]

The recursive predictor-based subspace identification (RPBSID) algorithm bears heavy computation burden in estimating the system state variables. In this paper, an improved RPBSID method is presented and applied to identify time-varying modal parameters of the spacecraft. Compared with the original algorithm, it does not need to construct the corresponding Hankel matrix in each time instant for the improved method when solving the state variables. The affine projection algorithm (APA) is used to implement recursive estimation of the state variables, thereby reducing the amounts of data in the identification process. Moreover, the state-space model and corresponding modal parameters of the time-varying system are determined recursively by the identified state variable. In the numerical simulation, the dynamics model of a satellite with large flexible appendages is established. Three cases that may factors the modal parameters to vary with time, such as the linear variation, step change and periodical variation are investigated. The improved RPBSID method is applied to identify the structural time-varying frequency and damping ratio parameters. Compared with the original algorithm, the results of the theory analysis and numerical simulation illustrate that the proposed method not only can effectively identify the system time-varying modal parameters, but also features higher computational efficiency. [ABSTRACT FROM AUTHOR]

This paper studies the problem of detumbling a non-cooperative space object with a high rotating speed. Firstly, the high temperature superconducting technology and eddy current brake technology are combined together and an eddy brake concept based on superconducting electromagnet is proposed. Then, the qualitative analysis on the technological feasibility of this eddy brake concept is conducted, and the advantages of this combined technology is concluded through the tradeoff analysis among several despin approaches. Furthermore, by applying the electromagnetic tensor theory, the exact magnetic field model and exact eddy current torque model that explicate the action mechanisms of the superconducting eddy brake are derived. Finally, considering the requirement of the practical despin task, the despinning simulation studies of the typical tumbling objects ranging from low speed spin to high speed spin and the objects rotating with nutational motion are performed. The simulation results indicate that the superconducting eddy brake can provide enough brake torque to the despin rotations up to 550 (°)/s or rotations combined with nutational motion. [ABSTRACT FROM AUTHOR]

The correlation relation is the credible method to predict the entry aerothermodynamics environment to avoid the deficiency for a wind tunnel experiment and numerical method in hypersonic vehicle design. In this paper, the suitability for the classical Stanton number-Reynolds number correlation relation is researched theoretically, which is deducted from the Kemp-Riddell formula at the stagnation point. The results show that the Stanton number-Reynolds number correlation relation is not universal and restricted with the Mach number, and the Stanton number-combination variable of Reynolds number and Mach number is more universal to correlate the wind tunnel and flight condition. Too low static enthalpy condition for a wind tunnel experiment will harm the correlation relation, which requires enhancing the inflow Mach number to compensate. Then several experiments are carried on 4 wind tunnels, several simulation results are also provided from several teams. The results validate the new correlation relation. [ABSTRACT FROM AUTHOR]

In order to analyze the accuracy of the BDS broadcast ephemeris, the laser ranging and precise ephemeris are used as the reference to do some analysis. Since there is no BDS-3 experimental satellite precise ephemeris, this paper designs the DBS-3 experimental satellite precise orbit determination experiment with a 3-day arc, and the results show that the orbit and clock offsets accuracies are about 50cm and 2ns respectively. Then combined with the BDS-2 post precision satellites ephemeris obtained from the international GNSS monitoring & assessment system (iGMAS), to evaluate the accuracy of the BDS-3/BDS-2 ephemeris-clock and ephemeris-orbit, in order to evaluate the ephemeris-orbit more accurately, the SLR observation data is used as an external means to evaluate the BDS satellite ephemeris-orbit accuracy, the Id RMS of the ephemeris-orbit and the STD of ephemeris-clock are counted, and the results show that most clock accuracies are better than 10 ns, the orbit accuracy is better than 5 m. In addition, in order to analyze the time-frequency performance of the ephemeris-clock, the frequency stability, the drift rate and the accuracy of the satellite clock offset are calculated. The experimental results show that the performance of the BDS-3 test satellites is generally better than that of the BDS-2. The performance indicators of the frequency accuracy, frequency drift rate and frequency stability calculated show that the BDS-3 satellite increases by 42.8% , 22.5% and 9.5% compared with the BDS-2. [ABSTRACT FROM AUTHOR]

This paper focuses on the pseudorange measurement error in the BeiDou satellite navigation system, comprehensively analyzes the measurement principle of the system, proposes the construction procedure of the system error index system, and constructs the BeiDou satellite navigation system measurement error index system based on the error gradation decomposition method. It consists of 51 indicators including a system-level indicator, 3 criteria-level indicators, 11 factor-level indicators, and 36 basic indicators. At the same time, in combination with an example, the absolute delay test requirement of the downlink of the navigation satellite leads to the problem of the absolute delay testing. The output port of the 1 PSS external to the satellite navigation task processing unit is defined as the time zero point of the satellite, and the path of the absolute delay that needs to be tested is given. According to the actual situation of the current engineering system, through the measurement error of each part, the measurement error accuracy of the entire absolute delay is obtained. [ABSTRACT FROM AUTHOR]

The scattering characteristics of a hypersonic near space vehicle are studied in this paper. The research takes into account the effect of the surrounding flow and wake on the radar cross section (RCS) of the near space hypersonic vehicle. The results show that the maximal plasma density of the surrounding flow, near wake and part of the far wake is higher than the critical plasma density of the ionosphere and much higher than the critical plasma density of the over-the-horizon radar whose frequency ranges from 3 MHz to 30 MHz. The plasma wake may be seen as conducting observation when the radar frequency is lower than the plasma frequency. So the RCS of the plasma wake is even larger than the hypersonic vehicle. On the basis of the numerical analysis，we suggest to detect the near space hypersonic vehicle by an over-the-horizon radar, which may provide longer reaction time for a radar warning system. [ABSTRACT FROM AUTHOR]

A seventh-degree orthogonal simplified cubature Kalman filter algorithm (7th-SCQKF) is proposed for the initial alignment of a strapdown inertial navigation system (SINS). According to the simplified CKF theory, this paper introduces the improved seventh-order simplified CKF algorithm (7th-MSSRCKF)，which improves the performance of the original seventh-degree simplified CKF (7th-SSRCKF). At the same time, on the basis of the 7th-SSRCKF and 7th- MSSRCKF, the 7th-SCQKF is proposed to improve the filtering accuracy. In the meantime, the seventh-degree simplified CQKF (7th-SCQKF) algorithm is applied to SINS' s large misalignment angle initial alignment simulation. It is proved that the filtering accuracy of the 7th-SCQKF is higher than that of the 7th-MSSRCKF, which verifies the correctness and validity of the new algorithm. [ABSTRACT FROM AUTHOR]

This paper proposes an autonomous orbit determination algorithm combining the short-term dynamics orbit determination technique and the free-net pseudo-inverse adjustment using the measurements of the bi-directional distance measurement of the inter-satellite link (ISL) in a navigation constellation. This algorithm solves the problem of the rank defect because of the lack of the start information of the position calculation by pseudo-inverse adjustment, at the same time, sets up the state transition between the epoch steps using the orbit dynamics to solve the problem of the velocity calculation. The results show that, after running autonomously for 90 days, the satellites' average user range error (URE) is less than lm (2σ)，better than the precision requirements of the autonomous operation of the navigation constellation, so the efficiency of the algorithm is verified. [ABSTRACT FROM AUTHOR]

For satisfying the requirement on all-timing launching in a mission and enhancing the adaptability of an astronautic system in a lightning environment, the development of the lightning protection technology for astronautic systems is reviewed in this paper. At first, the destructive lightning effects are introduced and some typical lightning accidents in the astronautic history are summarized. Some standards & documents on lightning protection are reviewed. Then a general review on the development of the lightning protection technology for an astronautic system is proposed，which involves the numerical simulation technology on lightning effect, some designation methods and testing methods on lightning protection for launch vehicles, the lightning weather prediction & detection technology, lightning rod systems and some artificial lightning protection methods for grounding systems. In the end，according to the lightning protection requirements of the domestic astronautic engineering, future development advices are provided，and main research ponits are emphasized. [ABSTRACT FROM AUTHOR]