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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]

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 analytic expression of the electrostatic potential near the spacecraft surface is obtained by solving the Poisson equation based on the electrostatic field theory, and the mathematical expression of the electric field intensity near the spacecraft surface is deduced. Using the boundary condition of the electromagnetic field, the dielectric surface potential-permittivity model is established, and the relationship among the dielectric surface potential, surface charge and permittivity is gained. Taking the practical cases for example, the change regulation of the surface charge with surface potential and the distribution of the electrostatic field near the spacecraft surface is discussed, and the effect of the dielectric constant on the surface charge and surface potential is analyzed. The results show that the electrostatic field induced by the dielectric surface charge decreases as the distance incrases when the surface potential of media is constant, and the surface potential of media decreases with the increase of the dielectric permittivity and tends to a stable value under the condition that the dielectric material has equal charge. Therefore, it is possible to select the dielectric materials with smaller permittivity under certain conditions to reduce their surface potential, and to reduce the probability of the electrostatic discharge between different media. [ABSTRACT FROM AUTHOR]

A method for calculating ihe translucent shadow is proposed in this paper for the needs of the design and simulation of the solar array of spacecraft with a large deployable antenna, which can cause translucent shadow. The proposed method builds 3D-model of the metal mesh with the minimum repeating unit to obtain the light transmission rate of the metal mesh under different illumination and builds up a table. When calculating the shadow caused by the metal mesh components, the position relation of the triangular face and the incident light is calculated firstly. The light transmittance of the triangular face is calculated by the table lookup and the light intensity of the projection area is reduced correspondingly. An example of the radial rib antenna shows that the method is fast and accurate. It can generate the light transmission mask pattern correctly, which lays the foundation for the simulation analysis oi the solar array. [ABSTRACT FROM AUTHOR]

Based on the Monte Carlo technology in statistics,combined with the theory of the intersection of a ray with a triangle,the Monte Carlo method for the calculation of Projected Cross-Sectional Areas( PCSA) of spacecraft has been proposed with elaborated procedures. The developed method is parallelized employing a shared memory programming model,Open MP,in order to take advantage of the multiple-core processors,which has been an industry trend for many years. Then,the PCSAs of a one-side circular plate and the SAMSON satellite in some typical attitudes are calculated,aiming at validating the Monte Carlo method and demonstrating its capability of dealing with complex geometries of engineering reguirements. The proposed Monte Carlo method could be applied to the SAMSON and GOCE satellites,with the purpose of computing their PCSAs in large quantities of attitudes,in order to provide input parameters for satellite attitude and orbit control. [ABSTRACT FROM AUTHOR]

The problem of the relative position and attitude coupled control for rendezvous and docking is investigated in this paper, which takes the external disturbances into consideration and assumes that the target spacecraft is freely tumbling. An adaptive 6-DOF control scheme is proposed based on the concept of the fixed-time stabilization. Besides, the singularity problem is solved through a switch function which not only makes the settling time estimable, but also the estimated value is independent of the initial values of states. Then the stability proof is accomplished by the development of a Lyapunov function. The numerical results show that this method achieves good performance and robustness. [ABSTRACT FROM AUTHOR]

In order to determine the relative position and attitude of a non-cooperative target, such as a failed spacecraft, an algorithm based on the texture boundaries is developed for ellipse extraction. It is assumed that the elliptical feature represents the boundary of the two different texture regions on the surface of the spacecraft. With the relative position and attitude information from last time, a discrete geometric model of the target is projected onto the image plane. The texture boundary points are detected by the method of probability along the normal direction of each discrete point. Then the points with large errors are eliminated by the random sample consensus (RANSAC). Subsequently, the parameters of the extracted elliptical feature are obtained. As the texture feature is robust lo changes in illumination, the proposed algorithm can extract the elliptical features rapidly and accurately in the image in the complex cases, such as the changes in illumination and unevenness of the surface reflection on the spacecraft. Considering the feature extraction of a docking ring as an example, the simulation is performed. The influence of the parameters and noise on the accuracy of the proposed algorithm is investigated, and the cost time of the result is analyzed. The proposed algorithm and the algorithm based on the gradient information are compared in real images. The results show that the proposed algorithm has high accuracy and low computational cost. [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]

In order to realize automatization in rendezvous and docking mission, a method of long distance autonomous rendezvous for spacecraft is proposed. A maneuver strategy adapted to long distance autonomous rendezvous is designed. The control parameters are obtained by the autonomous maneuver plan algorithm which contains the initial value calculating and accurate solution iterating. The quasi-mean element method combined with the mean atmosphere density method is used to reduce the on-orbit calculation quantity. The simulation result shows that the design variables of this method satisfy the terminal conditions well. [ABSTRACT FROM AUTHOR]

A sliding mode control-based robust control law is proposed to deal with the problem of spacecraft attitude tracking considering actuator misalignments and external disturbances. The control torque errors due to actuator misalignments are considered in the proposed control law, and its effects on attitude control performance are suppressed. Besides showing stability, explicit bound on the attitude tracking errors is given in terms of design parameters. Simulation results show the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

In order to solve the problems of temperature prediction concerned with the spacecraft thermal balance test, a particle swarm optimization algorithm of temperature prediction is proposed in this paper. According to the thermal balance temperature model, the objective function to be optimized and the temperature calculation process of thermal balance based on particle swarm optimization is established. Based on the prophase temperature data of a spacecraft thermal balance test, the thermal balance stable temperature and tranient temperature are predicted. By comparison . the error between the predicted data and the measured data are very little and acceptable. The results show that the proposed method can be effectively applied to temperature prediction of spacecraft thermal balance test. [ABSTRACT FROM AUTHOR]

A shielding effectiveness analysis method based on the equivalent admittance model is proposed to overcome the difficulty of dealing with VHF/UHF shielding of spacecraft. The aperture is treated as a waveguide. The horizontal capacitive model and vertical inductive model are derived from the variation method. The parameter matching admittances and width correction method are also researched. The shielding effectiveness math model is researched based on the transmission line theory. It proves the accuracy of the method and usefulness in dealing with the aperture with arbitrary position and length-wavelength ratio, and it can analyze the resonant effect. The method has been used in analyzing the shielding effectiveness of a telecommunication cavity, and the result comparisons have demonstrated the effectiveness of the approach proposed. [ABSTRACT FROM AUTHOR]

Prediction method and test validation techniques of vibro-acoustic mechanical environment of large complex spacecraft are presented in this paper. The vibro-acoustic modeling method for spacecraft is discussed based on hybrid finite element-statistical energy analysis (FE-SEA) method, then the satellite-level and systematic-level (fairing-spacecraft- instrument bay-adaptor assemblies) hybrid models are established respectively. In the end, the comparisons between prediction results and acoustic test results have demonstrated the effectiveness of the predication method and hybrid model, and the key issues related to the prediction precision are also discussed. [ABSTRACT FROM AUTHOR]

Single gimbal control moment gyros (SGCMG) system cannot afford accurate three axis torque in singular states. A singularity escape method is designed based on the analysis of singularity principle. Firstly, a new dynamic coordinate system is created and switched as the steering reference coordinate system. Secondly, one of the control dimensions is abandoned when the SGCMG system moves into the singular state and the system is considered as a redundant SGCMG control system within a plane. Thirdly, a null motion in the two dimensional space is provided so that the SGCMG can move out of the singular state quickly. Finally，the three dimensional steering law needs to be switched on after the SGCMG system escapes from the singular state. The method's impressive performance on singularity escape is demonstrated by the simulation results. [ABSTRACT FROM AUTHOR]

To extend the operational life of the failed spacecraft, the technology of spacecraft attitude takeover control is used to take over its attitude control systems. The uncertain dynamics of failed spacecraft and the change of thruster configuration will constitute a formidable technical challenge for attitude takeover control. Therefore, a takeover control strategy based on control system reconfiguration is proposed for the failed spacecraft attitude maneuver. Firstly, a command filtering backstepping control method is used to reconstitute the control law and the stability of the system is analyzed using the Lyapunov function. Moreover, the reconfiguration of the thrusters is implemented by reconstituting the configuration matrix of the thrusters. Furthermore, considering the fuel consumption and the control inputs limitation, the thrust forces reallocation is achieved by the dynamic control allocation method based on constrained quadratic program. The method proposed in this paper achieves the takeover control of the failed spacecraft whose fuel has been exhausted or whose actuators are partially failed. Numerical simulations validate the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

Single event protection is more and more important in the development of spacecraft. This paper firstly analyzes the characteristics of the impact of single event soft errors on the spacecraft, and then establishes a criticality model for evaluating the impact of a single event soft error on spacecraft. Finally, a weakness identification method and the steps of single event protection are presented, which results provide an objective basis for improving the single event protection design. [ABSTRACT FROM AUTHOR]

Under the influence of the space environment, the organic pollutants applied in the spacecraft have the potential to degrade performance of the sensitive components or devices. In order to control the molecular contamination on-orbit, a method for the zoelite molecular sieve due to its adsorption of organic molecular contamination is proposed in this paper. The absorption capacity of Naβ, NaY and 13X in vacuum is studied with contaminant source from outgassing of cables. It is found that 13X is the best adsorbents compared to Naβ and NaY, and its absorption capacity is 14. 03%. Zeolite-coated cordierite molecular absorbers can be used to collect and retain outgassed molecular effluent emanating from spacecraft materials, thus effectively controlling the contamination of the critical sensitive surfaces to enhance reliability. [ABSTRACT FROM AUTHOR]

Attitude tracking problem with unknown friction torques of reaction wheels and external disturbances is addressed. A robust adaptive controller with parameter update law is proposed and analyzed. An indirect (nonregressorbased) approach used to deal with the effects of unknown friction torque and external disturbances is explored for the attitude control law. This is done by not focusing on friction torques and external disturbances, but on their bound, thus allowing the core information on friction torque and external disturbances to be extracted and used for controller design. The stability of the resulting closed-loop system is proved by application of Barbalat ' s Lemma. Numerical simulations are presented to show the effectiveness of the proposed attitude tracking approach. [ABSTRACT FROM AUTHOR]

To solve the problem of acquiring the load force function description in the process of spacecraft pyroshock environment prediction,a ‘source system-near field structures 'integrated modeling and analyzing method based on Hydrocodes is proposed to analyze the shock processes of the spacecraft-launch vehicle separation mechanisms and other release mechanisms triggered by pyrotechnicsin spacecraft. By using this method,the force time history can be computed,so that the decoupled analysis of the shock can be realized. The analysis of a clamp-band separation structure is taken as an example to illustrate the feasibility of the method. Both the integrated( coupled) model and the decoupled model are constructed and computed,and both comparison and analysis of the computational results preliminarily illustrate the feasibility of the method. Further studies including a series of coupled studies and a simplified model study are also implemented to prove the accuracy and the rationality of partially modeling of the method. In conclusion,this method is a feasible way to acquire the exact function of the pyroshock load force in spacecraft,and provides a basis for the prediction of the spacecraft pyroshock environment. [ABSTRACT FROM AUTHOR]

The arrangement of a heat load with certain temperature in the single-phase active thermal control system that has a low-temperature inner loop, a middle-temperature inner loop and an external loop is discussed, and the arrangement principle is proposed. The total system mass is investigated with Lagrange multiplier method based on the mathematical model of system mass and energy balance relationship. The result shows that there exists a critical heat load temperature at which the total system masses are equal. When the heat load temperature is lower than the critical value the system has lower total mass with the heat load arranged in the low-temperature internal loop. On the contrary, the system has lower total mass with the heat load arranged in middle-temperature internal loop. The heat load arrangement depends on its temperature and power. Finally, the arrangement principle is discussed qualitatively based on the arrangement of temperature difference. [ABSTRACT FROM AUTHOR]

A dynamics modeling method is presented for spacecraft with flexible appendages. The dynamics equations are derived taking into account the geometric nonlinearity and coupling deformation terms caused by a large overall motion. And then the nonlinear strain-displacement relations are introduced, and the nonlinear dynamics model of spacecraft is deduced according to the virtual work principle. The complete expressions of geometric nonlinearity and dynamic stiffness terms are considered in the dynamics equations. Spacecraft dynamics are analyzed for linear model and nonlinear model respectively. By comparing these models, both correctness and accuracy of present nonlinear model are verified. Because geometric nonlinearity and dynamic stiffness terms are ignored in the traditional linear model, it is not suitable for dealing with large deformation rigid-flexible problems under the condition of a large overall motion. Furthermore, as the rotational speed increases, efficient and accurate prediction of dynamics behavior for spacecraft with flexible appendages is achieved by using the present nonlinear model. The above conclusion has important academic value and engineering significance. [ABSTRACT FROM AUTHOR]

A novel nonsingular saturated terminal sliding mode (NSTSM) based control law is investigated for a rigid spacecraft, in which the actuator control input saturation and even external disturbances are explicitly considered simultaneously. Specifically, in this proposed control scheme, the fast convergence of spacecraft attitude maneuvering is achieved, and also singularity can be avoided in comparison with traditional terminal sliding mode, the spacecraft is allowed to perform the given operations within the saturation magnitude. It is important to note that the results of this paper are derived with respect to magnitude saturation and under the condition of no additional restrictions on upper bound of disturbances, and need not to make any small-angle assumption. The stability analysis further shows that the controller ensures the closed-loop system to converge to the small neighborhood of the sliding surface fast and then to the small neighborhood of the equilibrium point, and has better robustness to external disturbances. The attitude maneuvering performance of the controller is evaluated by using a numerical example. [ABSTRACT FROM AUTHOR]

A robust controller design method for spacecraft autonomous rendezvous in an elliptic orbit is developed. LAWDEN equation with time-varying parameters is used to model the elliptic orbit rendezvous dynamics and a linear model with uncertainties of elliptic orbit rendezvous is obtained by classifying the time-varying parameters. The H∞ theory is employed to design the robust control law for autonomous rendezvous based on linear matrix inequality (LMI) in the presence of disturbances, and quadratic D stablility analysis for the controller based on LMI is given to optimize the transient performances of the close-loop systems. The proposed controller is a constant-gain linear controller, and easy to implernent in engineering. Simulation results indicate that the controller can implement autonomous rendezvous in the elliptic orbit. [ABSTRACT FROM AUTHOR]

An approach for spacecraft single wall ballistic limit prediction is proposed based on nonlinear nonseparable support vector machine (SVM). The test data are used to train the SVM, and the separation plane of both penetration and non-penetration points is built. The trained SVM can be used for new case predictions. The training problem of SVM is a quadratic programming problem. The constraint of the optimization is the correctness of the test data classification and the aim of the optimization is maximizing the confidence of the classification. The Lagrangian dual theory is introduced to solve the training problem. With adding the upper boundary to the Lagrangian multipliers, the nonseparable data set is handled. Quadratic kernel function is introduced to extend the SVM approach to nonlinear problem. The test data are effectively classified with the quadratic kernel function SVM. The hypervelocity impact test data are used for the SVM prediction model verification. The results show that the SVM approach is feasible, and the accuracy is higher than NASA JSC single wall ballistic limit equation. By separating the variable of projectile diameter from the classifier equation, the SVM ballistic limit equation is built. [ABSTRACT FROM AUTHOR]

The edge heat leakage will generate if the shields in multilayer insulation (MLI) can't form a closed system, thus producing certain effect on the performance of heat insulation. The two dimensional steady state and combined radiation/conduction heat transfer in MLI is modeled by using the finite element method to simulate the thermal loss from edge of MLI. The effects of design parameters such as mounting area, layer density, thermal conductivity and emissivity of pressure-sensitive tape on the edge heat leakage are analyzed. Two cases that whether the boundary of MLI is covered or not are compared to decide which one is better in heat insulation. Based on the analysis results some useful designs that help to reduce thermal loss from edge of MLI are proposed. [ABSTRACT FROM AUTHOR]

As the shaded effect must be fully taken into account in the electrical and thermal design of spacecraft's solar array, a method for accurately calculating the shadow of solar array is proposed. Firstly, the triangular grid method is used to construct the 3D model of spacecraft, secondly, the relative motion among the spacecraft components is considered, then a "bounded box" is used to intercept the triangular grid points of the model, and these points are projected to solar array plane, finally point by point comparing method and minimal rectangle method are used to generate the shadow graph. The example of lunar rover's shadow calculation is given to validate the proposed algorithm. Simulation analysis shows that the minimal rectangle method costs less time in generating the shadow graph. The algorithm proposed in this paper can calculate the shadow of solar array which is shaded by complex spacecraft whose components have relative motion. And meanwhile accurate shadow graph which is be generated, thus laying foundation for the calculation of the output characteristics of the shaded solar array. [ABSTRACT FROM AUTHOR]

Numerical analysis based on finite element method and aerothermoelastic behaviors of temperature-dependent Functional Graded Panels (FGP) in supersonic or hypersonic flows are investigated in this study. Considering the nonlinear distribution of temperature along the thickness direction of the panel, a more available aerothermoelastic model of FGP is established. The aerodynamic heating effect is simulated by use of Eckert's reference temperature method, then thermal stresses and physical properties of the panel are obtained by solving the Heat Conduction Equation by use of the Finite Element Method. Finally, solving the governing equation of FGP by use of the Finite Element Method, the vibration behaviors due to aerothermoelasticity are studied. From the simulation results, it can be found that, the numerical analysis is effective and efficient, and the effects of aerodynamic heating can make the panel turn into thermal buckling state or vibrating state easily. And it is also found that, the panel behaviors are very sensitive to the initial condition when the non-dimensional aerodynamic force is in a certain 'transition region'. As a conclusion, it can be drawn that the model and numerical method presented in this study could be used to study the aerothermoelastic behaviors of FGP accurately and feasibly. [ABSTRACT FROM AUTHOR]

To improve the thermal control adaptability of spacecraft, a novel thermal control system has been proposed, a thermostatic valve with sensitive wax having the automatic proportional control characteristic of flow and temperature is applied in a single-phase fluid loop thermal control system. Further, the mathematical model including thermostatic valve with sensitive wax, heat load, radiator and other components is built by using the lumped parameter method and calculated by using the numerical simulation method to analyze the temperature dynamic performance of the thermal control system. Finally, the simulation result shows that the layout of the thermostatic valve with sensitive wax and temperature-response characteristics of sensitive wax such as phase-change range, time constant and temperature delay have great effect on dynamic performance of the thermal control system. This conclusion can provide theoretical basis for the optimal design of single-phase fluid loop based on thermostatic valve with sensitive wax. [ABSTRACT FROM AUTHOR]

For measurement problems of attitude and position parameters in the process of rendezvous and docking for spacecrafts, changes of intrinsic parameters of the camera mounted on the spacecraft in orbit under the influence of space environment are taken into account. A linear method is proposed and its main feature is in that the camera only shots three cursor images, without needing to know any geometric information of the group of the cursor points. By calculating the geometry of circle points, and establishing the constraint equations of the absolute conic on the camera intrinsic parameters, camera intrinsic parameters can be solved linearly. Simulation experiments show that the method is effective in the rendezvous and docking for spacecrafts. The calibration of camera intrinsic parameters has simple, real-time and robustness features. [ABSTRACT FROM AUTHOR]

An in-plane maneuver detection method based on orbit perturbation is proposed in this paper to solve the maneuver detection problem of incomplete orbit information of LEO spacecraft that can't propagate directly. Semi-major axis and eccentricity are chosen as characteristic parameters in this method. The orbit parameter boundary of target spacecraft is established by analyzing the effect of atmosphere perturbation and J2 perturbation on LEO spacecraft orbit. By comparing with the actual orbit parameter., whether the data point detected is in the normal boundary can be judged. At last, the orbit parameter of X-37B is detected by this method, and 10 maneuver points exist. The detection result has demonstrated the effectiveness of the approach proposed. [ABSTRACT FROM AUTHOR]

A backstepping design based adaptive control algorithm is developed for attitude stabilization of a rigid spacecraft, in which the uncertainties of actuators misalignment and external disturbances are considered. Lyapunov stability analysis shows that the attitude and angular velocity converge to zero, and an novel updating law is employed to implement attitude control law as well, in which the possible singularity problem caused by the estimation of uncertainties due to actuator misalignment is avoided effectively. In addition, a dynamic control allocation is investigated to distribute the desired control command among redundant actuators. This method extends the conventional quadratic-programming control allocation by penalizing the previous step before sampling intervals and minimize the energy consume. Finally, a numerical simulation example for a spacecraft attitude control system is included to illustrate effectiveness and feasibility of the proposed control scheme. [ABSTRACT FROM AUTHOR]

The multi-layer optical windows are usually installed in spacecraft for scientific observation, in which the homogeneity of temperature distribution has effects on image quality. In this paper, considering semitransparent and specularly reflecting interfaces, based on the ray tracing-node analysis method, a multi-layer transient coupled radiative and conductive heat transfer model is used to examine the effects of thickness and the number of heat insulation glass layers on temperature distributions of the multi-layer optical windows. The changes of absorption coefficient and refractive index of the optical window changing with wave length are approximately expressed by using a set of rectangular spectral bands. The study shows that in outer space, thermal radiation plays a very important role in the cooling process of the multi-layer optical window, and in the very thin layer of glass medium very close to the surface of glass layer, the radiative heat flux and the conductive heat flux are coupled with each other intensively. The thinner the insulation glass layer is, the more homogeneous the temperature distribution therein is, thus helpfully improving the image quality. The more the number of insulation glass layers are, the more homogeneous temperature distribution of the multi-layer optical window is, thus also helpfully improving the image quality. Also determination of the optimized number of heat insulation glass layers needs to consider the other factors. [ABSTRACT FROM AUTHOR]

A mathematical model is built for some spacecraft and its package, and FLUENT software was used for model calculation of the coupling between fluid flow and heat transfer. The passive heat preservation performance of the package is calculated by using the transient state solver of FLUENT under three different environment conditions. It is found from calculation that the temperature inside the transportation package could be kept at 0°C ∼ 40°C with the help of the passive heat preservation under two extreme environment conditions, thus meeting the temperature requirements of spacecraft transportation. The computational results indicate that the capability of the passive heat preservation of the transportation package is sufficient enough to protect the spacecraft in transportation process. Besides, from solutions for the third environment conditions it is found that the time of the passive heat preservation of the transportation package is less than 12 hours both in the extreme cold and hot environments. [ABSTRACT FROM AUTHOR]

The black antistatic thermal control film has been successfully fabricated. Through inorganic-organic technique its environmental adaptability tests such as thermal cycle, hydrothermal aging, ultraviolet irradiation, proton irradiation, electron irradiation are made. The test results show that the black antistatic thermal control film has very good performance. [ABSTRACT FROM AUTHOR]

For the attitude control system of a spacecraft, non-smooth control technique is utilized to improve the robustness and dynamic performance. A continuous attitude control law is given to ensure the homogeneity of the closed-loop attitude control system with a negative degree of homogeneity. The resulting attitude control system is finite-time stable, thus guaranteeing the dynamic performance of state variables. Simulation is carried out under the cases of the nominal system and the systems with parameter uncertainties and external disturbances, respectively. The simulation results show that, under the designed control law, the nominal system is finite-time stable, and uncertain systems are robust against uncertainties and disturbances. [ABSTRACT FROM AUTHOR]

Specification of spacecraft mechanical environment is the essential input for design and testing of spacecraft and its payloads, which could directly affect the level of the spacecraft design. Along with the rapid development of space industry, higher payload capability is demanded for modern spacecraft due to the new missions, whereas the mechanical environment analysis and specification determination have been the bottlenecks for payload ratio increase of spacecraft in China. In this paper, a research review of the mechanical environment prediction methods, finite element modeling & model updating and specification determination methods, which are the key techniques related to the mechanical environment analysis, is presented. In the end, according to the requirement of the domestic space engineering, the main research directions in the spacecraft mechanical environment analysis and specification determination are emphasized. [ABSTRACT FROM AUTHOR]