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In this paper, a Taylor-series location method and its performance analysis are presented in presence of sensor position errors for general measurement equations. Two cases in the absence of calibration sources (a) and in the presence of calibration sources (b) are discussed. For the case (a), two Taylor-series iteration formulas are given, and their theoretical performances are proven to be consistent with each other, and equal to the corresponding Cramér-Rao bound (CRB). For the case (b), the Taylor-series location formula based on the difference calibration (DC) location is derived. Aiming to the shortcoming of the DC location technique, the Taylor-series iterative method based on two-step optimal fusion is proposed, whose theoretical performance is proven to reach to the corresponding CRB. Finally, some simulation experiments for two passive location scenarios are conducted to verify the effectiveness of the location algorithms and the performance analysis in this paper. [ABSTRACT FROM AUTHOR]

A frequency estimation algorithm for the deep space telemetry, tracking and control (TT&C) system under low Carrier-Noise-Ratio (CNR) and high dynamic conditions is presented in this paper. Considering the drawbacks of the exist algorithms, an advanced closed loop carrier tracking algorithm based on the unscented Kalman filter (UKF) is proposed. This new algorithm combines the advantages of the discriminator of the frequency lock loop and UKF to obtain a wide estimation range, high estimation accuracy and low CNR threshold. In addition, it is found on the basis of the analysis of the two kinds of models that this new algorithm cost much less computational effort than the conventional UKF. The high dynamic trace of receiver is simulated in this paper. The results show that the proposed loop structure can apparently improve dynamic capability, convergence performance and tracking accuracy, thus effectively completing the task of frequency estimation under low CNR and high dynamic conditions. Compared with the frequency estimation algorithm based on extended Kalman filter (EKF), this new algorithm has a much smaller frequency estimation error so that it will have prospective application potential. [ABSTRACT FROM AUTHOR]

Two methods of Earth orientation determination are proposed by using dual cone earth sensor in this paper. One is based on the assumption of spherical earth, and for the other method the effects of earth's oblateness is considered. A least square navigation algorithm with earth's oblateness correction is also presented in this paper. Monte-carlo simulation results show that the navigation algorithm with earth's oblateness correction can achieve of position accuracy 800m (3δ) and 2.4m/s (3δ) velocity accuracy under measurement noises of 0.1° (3δ) for the earth sensor and 0.05° (3δ) for the sun and moon sensor. [ABSTRACT FROM AUTHOR]

This paper focuses on an investigation into non-contact shape control of a beam with surface bonded photostrictive actuators. The operating mechanism of PLZT photostrictive actuator is discussed in this paper and an optoelectromechanical finite element model is developed for accurate analysis of muhiphysics' effects with optical-electricmechanical-thermal coupling. The Enhanced Assumed strain and Assumed Natural strain methods are used to improve the element's performance. Based on both genetic algorithm and finite element analysis, a general method of non-contact shape control for the beam is presented by using PLZT photostrictive actuator. In this method, the light intensity acting on photostrictive actuator are chosen as a design parameter and shape errors between the desired shape and the achieved shape are taken as an objective function. Numerical simulation results show that this method is robust and effective, and can well realize the non-contact shape control of a beam with surface bonded photostrictive optical actuators. [ABSTRACT FROM AUTHOR]

Considering the current detection methods are insensitive with soft fault and have large delay problem, by analyzing the basic principle of wavelet singularity being used in fault detection, a algorithm based on modulus maximum principle is proposed in this paper for fault detection of navigation sensors, in this algorithm, only the observation signals of sensors are used to detect fault. The theory of wavelet singularity fault detection and algorithm process are presented in the paper. The algorithm can be used to effectively detect soft faults of the navigation sensors which is difficult to detect and determine the type of faults through the Lipschitz exponent. It can keep the reliability of fault-tolerant integrated navigation system. Simulation results show that the proposed method is effective and practicable. [ABSTRACT FROM AUTHOR]

According to the special requirements of the acquisition time and carrier frequency for strapdown inertial navigation system (SINS)/BeiDou tightly integrated navigation system under high dynamic environment, an algorithm based on zoom-fast Fourier transformation (Zoom-FFT) that receiver captures BeiDou B1 signal with SINS is put forward in this paper. The algorithm optimizes the traditional algorithm, the parallel code phase acquisition method based on fast Fourier transformation(FFT). Then, it designs a high dynamic source for simulation and verifies the algorithm. The simulation results show that this method reduces 50% cold start-time than that without aid, the warm start-time is only about 2%, and the sensitivity of the system is improved. At the same time, the estimated carrier frequency resolution increases by more than 50 times, and the error is less than 10Hz. The optimized algorithm can meet the requirements of tracking loop in the deeply integrated navigation system under high-dynamic environment, and improve the system acquisition performance. [ABSTRACT FROM AUTHOR]

In order to compensate the range and azimuth shift variations of the echo model in geosynchronous synthetic aperture radar (GEO SAR) imaging, an algorithm based on improved range-doppler and azimuth chirp scaling (RD-ACS) is proposed in the paper. First, the slant range model with 4-order Taylor expansion is introduced to solve the curved trajectory problem in GEO SAR imaging. Then, the conventional range-doppler algorithm (RDA) is improved to compensate the range shift variation. And, an additional azimuth chirp scaling (ACS) is designed to compensate the azimuth shift variation according to a new azimuth-variant model. The 2-dimensional (range and azimuth) focusing scope in GEO SAR imaging is enlarged obviously. The validity of the new algorithm is validated by the simulations with the space borne radar advance simulator (SBRAS). [ABSTRACT FROM AUTHOR]

To characterize physical properties of a scattering object, a steady and fast algorithm of super-resolution SAR imaging is proposed based on attribute scattering center in this paper. An improved Orthogonal Matching Pursuit (OMP) algorithm is utilized to estimate the parameters of simplified attribute scattering center model. Based on the model parameters, two-dimensional spectrum extrapolation is preformed in signal reconstruction to achieve super-resolution SAR imaging. The method has fast computational efficiency and can accurately describe the physical structure compared with the traditional super-resolution algorithm based on the point scattering model. In addition, the initial orientation angle can be used to achieve a better focusing performance. The simulation results validate the superiority of the proposed algorithm. [ABSTRACT FROM AUTHOR]

In modern electronic warfare, for the direction finding of multiple wideband coherent radiation sources under the background of decoys, the algorithms for signal number estimation and direction finding of multiple wideband coherent radiation sources are presented based on single baseline in this paper. Firstly, new signals are created by using conjugate multiplication of signal spectrums received by two antenna arraies. According to the spectrum architectural feature of new signals, the number of radiation sources can be estimated. In case the number of sources is given, by using the fractional time delay estimation algorithm based on the wideband signal phase spectrum, the time delays between radiation source signals received by two antennas can be got indirectly. So the directions of these radiation sources can be found according to the time delays. The algorithms have the feature of simple equipment and only the single baseline composed of two antennas is required. The simulation results show that the number of multiple wideband coherent radiation sources can be estimated accurately and directions of multiple radiation sources can be found accurately under certain condition. [ABSTRACT FROM AUTHOR]

For evaluating the performance of sophisticated weapons, this paper studies a 2D imaging algorithm for the high-velocity moving target in short-range. The target velocity is estimated by using quasi wave-front of the warhead scattering centers, and a set of range points is got. Then, by deriving the target motion state equation, subsets of range points corresponding to each scattering center are extracted. Finally, target points corresponding to each scatter center is got by utilizing the range point migration (RPM) algorithm. The influences of sampling interval, velocity error and white noise on the imaging performance are analyzed. The simulation results show that target boundary is accurately extracted by using the proposed method, which is conducive to get a more accurate measurement of target parameters. [ABSTRACT FROM AUTHOR]

The widely used positioning methods fail to satisfy the increasing demand of users. Researchers develop a new GNSS Positioning strategy, called GNSS Cooperative Positioning, based on the concept of Cooperative Positioning (CP) in acquiring real-time positioning information of mobile robots. An in-depth survey of GNSS Cooperative Positioning, including its history, types of CP, basic idea, key steps of algorithm is presented in this paper. Current research results of GNSS CP show that this new positioning strategy gets equal or better positioning accuracy with less time cost compared with Assisted GNSS (AGNSS). [ABSTRACT FROM AUTHOR]

In order to increase the lower interception performance of the datalink, an optimal energy control algorithm based on the spatial information is proposed in this paper. Radiation power and starting time are selected as optimized variables, which are based on the threat factor of the target region and the real-time spatial information of the datalink. A mathematical model of multi-objective optimization is established to achieve minimum radiation power and energy cost. The hybrid chaotic particle swarm optimization (HCPSO) is used for the optimization of the energy control, and the solution which minimizes the two target functions is selected as the optimization solution. Compared with the constant radiation power method, the simulation results show that the proposed algorithm consumes less energy and has better performance of RF stealth. [ABSTRACT FROM AUTHOR]

To solve the problem of virtual aperture imaging for colocated multiple-input multiple-output (MIMO) radar under single snapshot, the virtual aperture array is analyzed for the MIMO radar and the echo model of polar format is built in this paper. The spatial spectrum transformation based on scale transformation of the range and azimuth domains is analyzed. It is pointed out that scale transformation of the azimuth domain can not be considered as the Keystone transformation for MIMO radar. A new fast polar format algorithm (PFA) is proposed. Simulation results verify the effectiveness of the method. [ABSTRACT FROM AUTHOR]

The non-uniform array made up of different-direction antennas has unique advantages for the DOA measurement of radiant point, and it has been widely used in ELINT. Because of the transmission factors of multipath transmission and ionospheric refraction, more and more elliptic polarized signals present to ELINT applications. The existing DOA measurement method of the non-uniform array can't be applied for the elliptic polarized signals because of the DOA measurement bias. The influence mechanism of the electromagnetic wave polarization and antenna polarization on the DOA measurement is studied in this paper, and a DOA measurement method based on the radial symmetry of two elements array of the non-uniform array is proposed, which is capable of measuring DOA of arbitrary polarization signal. It is great significant to the development of non-uniform array technique. The proposed algorithm is validated by simulation results. [ABSTRACT FROM AUTHOR]

In this paper, an improved algorithm is proposed for mixing matrix estimation in underdetermined blind source separation (UBSS). In the algorithm, the single source points in the time-frequency (TF) domain are detected first. Then, those single source points which deteriorate the mixing matrix estimation accuracy are removed. Finally, the mixing matrix is estimated by using a clustering method. It is experimentally shown that the proposed algorithm estimates the mixing matrix with high accuracy and robustness compared with existing algorithms. [ABSTRACT FROM AUTHOR]

A novel control algorithm based on the navigation function of line-of-sight and backstepping method is presented in this paper for spacecraft maneuver under pointing constraints and input saturation constraint. The navigation function of line-of sight is constructed on the unit sphere, and thereafter is used to design the backstepping controller. With the assistance of auxiliary system, a controller is obtained. The controller can not only satify pointing constraints, but also meet input saturation constraint, meanwhile the constant disturbance can be estimated and be suppressed. The simulation results validate the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

In traditional Kalman filtering algorithms, optimization estimation cannot be achieved for practical problems because the dynamics system model and noises are unknown. Firstly the impacts of various error sources and interval matrix operations in the traditional Kalman filter are analyzed. The analysis shows that the interval operation can ensure the completeness of set mapping but can not be the optimization. Based on the analysis, a new interval Kalman filtering algorithm is proposed in this paper. In the algorithm, various error sources are reduced to a priori estimation interval and a posterior estimation interval and the interval intersection set operation is adopted to achieve the optimization. This algorithm has comparable computational complexities with the traditional one. Simulations show that the proposed algorithm can achieve a 2dB gain over the traditional Kalman filter in high dynamic navigation and positioning with time-varying noises. [ABSTRACT FROM AUTHOR]

Coning effects must be accurately compensated in the attitude updating of the classical strapdown inertial navigation integration algorithm. These effects are not involved in the velocity updating, though the attitude change is being taken into it. The novel velocity error term induced by the coning correction is studied in this paper. These effects as the gyro angular increment data have the influence on the velocity updating in the same way. For the assumed linear ramp model, a two-sample compensation algorithm for the novel velocity error term is deduced in detail by using the two successive integrated angular rate increment and specific force increment measurements. The weighting coefficients are then optimized for best average performance in a specific environment; i. e. the body is exposed to a coning angular vibration about the x axis of the body frame combined with a linear vibration at the same frequency and in phase along the z axis. The simulation results validate that the two-sample optimization algorithm can compensate the integrated term of the novel velocity error effectively. [ABSTRACT FROM AUTHOR]

In view of the blind symbol synchronization problem of ZP-OFDM system in low SNR and multipath channels, a blind symbol synchronization algorithm for ZP-OFDM systems based on spectral entropy is proposed. The training data are not needed and the ZP-OFDM signal is calculated by using the double windows to get the spectral entropy ratio. The symbol synchronization is implemented by finding the peak point. The steps and capability analysis are provided in the paper. The disadvantage of the energy detection method affected easily by the channel noise is overcome by the algorithm which calculates the entropy with power spectrum of received signal. The window width is not needed to be adjusted according to channels. The simulation results show that this algorithm has superior performance in low SNR and mullipalh channels. [ABSTRACT FROM AUTHOR]

Direction finding system has strict requirement for the band width, angle measurement accuracy and direction finding range. To solve this problem, the frequency response and impedance-bandwidth characteristic of receiving antenna are designed based on a reconfigurable technique, and the demand of wideband for the direction finding system is satisfied. And in this paper, the traditional n amplitude-comparison bearing discriminator (nABD) comparing amplitude direction finding algorithm is studied on the basis of the designed antenna pattern, and a dynamic adjustment method of antenna weighting coefficient is proposed to get the better accuracy and range of direction finding. The simulation results show that the designed antenna has wide frequency range and appropriate reconfigurable notched band, and the proposed algorithm can obtain better resolution and greater direction finding range. [ABSTRACT FROM AUTHOR]

In this paper, a new wavefront curvature compensation method based on digital spotlighting preprocessing is proposed. First, digital spotlighting preprocessing, filtering and downsampling in 2-dimensional space domain, is performed on echo data. This generates multiple full-resolution phase histories of smaller image patches, each corresponding to a narrow-beam phase history data where the wavefront curvature effect can be ignored. Due to the inherent non-planar motion compensation capability, PFA is used to produce focused fine resolution image for each small patch. Finally, all focused image patches are seamed together to get a full image. Simulation experiments show that the new algorithm has improved focused scene size when applying to phase history generated by non-ideal radar flight path. [ABSTRACT FROM AUTHOR]

The three-dimensional (3-D) images of space targets with spaceborne along/cross track millimeter-wave (MMW) interferometric inverse synthetic aperture radar (In-ISAR) is studied under the condition of low SNR input in this paper. Because the traditional Range-Doppler (RD) algorithm can't get good performance when the target size is large and required high resolution. The wave number domain imaging algorithm is introduced to obtain two-dimensional (2-D) high resolution images of space moving targets. Then along/cross track interferometric processing is implemented for the three 2-D images obtained from three antennas to determine 3-D positions of the target scattering points. As the foundation of 2-D imaging and image registration, target detection and 3-D velocity estimation at low SNR input are studied here. The requirement for velocity estimation accuracy is analyzed. Finally, numerical experimental results are given to demonstrate the effectiveness of the along/cross track In-SAR system. [ABSTRACT FROM AUTHOR]

The computational burden of cross ambiguity function is very large for estimating the DTO (Differential Time Offset) and DFO (Differential Frequency Offset) when processing huge data, and general algorithms are difficult to meet the real-time requirements. A method for estimating DTO and DFO based on Integrate-and-Dump filters is proposed in this paper. According to performance analysis of the filter, appropriate decimation factor is determined. Then, the computational burdens for both coarse estimation and fine estimation are reduced significantly without affecting estimation accuracy. In the fine estimation, the mixed product signal can be decimated to five sampling points and operated by using CZT to achieve estimation of DTO and DFO with high accuracy. The simulation results validate the proposed algorithm. [ABSTRACT FROM AUTHOR]

In this paper, a unified representation of relative position and attitude based on dual-quaternion is proposed for RVD spacecrafts, which is a breakthrough to the traditional patterns for treating position and orientation separately. First, the model of relative position and attitude of RVD spacecrafts is established by using binocular vision and dual quaternion. Different from the traditional methods such as Euler angles and quaternion, this model has a very simple and unified form. And then, the two-step algorithm is proposed to solve the model. Simulation results show that this algorithm can satisfy the measurement requirement for the spacecrafts, and it has strong stability. So it is of great value to real-time on-orbit measurement of relative position and attitude for RVD spacecrafts. [ABSTRACT FROM AUTHOR]

Under the condition of a short sampling period, limited resource and computational capacity, a method for designing reduced-order fault detection filtering algorithm is proposed in this paper. Small perturbation theory and a Taylor series expansion about the balance point are used to linearize the nonlinear dynamics equations of space vehicles. Then the reduced-order fault detection filter is designed for the linear state-space equation. The problem of feasible solution of the reduced-order fault detection filtering algorithm is transformed into a nonconvex optimization problem expressed in terms of linear matrix inequalities. The local optimal solution of the nonconvex optimization is achieved by an alternate mapping algorithm. The reduced-order fault detection filtering algorithm is obtained under the condition that the feasible solution exists. Finally, the reduced-order fault detection algorithm is applied to the fault detection of the yaw control system in a small-scale autonomous helicopter. Simulation results are presented to show effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Low-thrust phasing maneuver design of Earth circle-orbit satellites is researched in this paper. A semi-analytical phasing parameter analysis method is proposed, and based on that an efficiently accurate design method is developed. First, according to the influence law of thrust direction on phase change rate, functional relationship between phasing parameters are derived by using orbit averaging technique and thrust direction assumption. The key phasing parameters can be obtained by using simple differential correction. Then, the fuel-optimal phasing orbit design under the condition of complex constraints based on a perturbation model is transformed into a multi-parameter optimization problem by discretizing control law. With the initial guess obtained by the analysis method, the problem can be solved rapidly by using a sequential quadratic programming algorithm. Finally, the simulation results of Geosynchronous orbit low-thrust phasing transfer is presented, it is shown that feasible initial guess can be provided with the analytical method for phasing orbit design, and by using the robust design method, low-thrust phasing trajectory design problem can be solved effectively under the perturbation model. [ABSTRACT FROM AUTHOR]

Considering the different transition modes of any two adjacent targets observed by a satellite, the complex scheduling constraints including slewing time, storage capacity and power are analyzed in this paper. Also, the acyclic directed graph model with a dynamic topological structure is established. In addition, the concept of constraint non- dominant path is proposed, and a dynamic path search algorithm (DPSA) based on label update is suggested. Experimental results show that the DPSA algorithm can greatly improve the scheduling quality at the expense of timing complexity and space complexity. [ABSTRACT FROM AUTHOR]

n order to improve both robustness against disturbances and sensitivity against faults and reduce the design conservativeness for the model uncertainties and unknown inputs, a design method of the H_/H∞ fault detection observer is presented in this paper, the non-convex constraint formulations can be converted into linear matrix inequality (LMI) constraints through lossless S-procedure, the design of the H_/H∞ fault detection observer can be transformed into the convex optimization problems with LMI constraints by making use of Schur theorem. The adaptive threshold generators are designed for decreasing the rates of false alarming. According to the numerical calculation of the convex optimization problems, the design of the fault detection observer process can be easy to achieve. The proposed algorithms guarantee the optimization trade-off between the robustness to the unknown inputs and the sensitivity to faults. Simulation shows that the proposed algorithms ensure the convergence of the residuals quickly and decrease the fault detection time. [ABSTRACT FROM AUTHOR]

The performance of PMF-FFT code acquisition algorithm under different frequency offsets is analyzed in this paper. Focusing on the detection performance degradation under partial frequency offset caused by the low frequency estimation accuracy, an improved code phase and Doppler shift united acquisition method is proposed. First, a set of matched filter outputs are obtained based on the partial matching filter (PMF) algorithm; then a low complexity and high-accuracy iterative frequency estimation algorithm is proposed by using the magnitude difference of the PMF-FFT output, and the frequency offset estimation is used to compensate the PMF output, thus improving the accuracy of frequency estimation and signal detection probability at the same time. Simulation results show that the algorithm can effectively improve the frequency estimation accuracy and the detection probability, and has very low complexity. [ABSTRACT FROM AUTHOR]

Since the existing side-peak cancellation method (SCM) is still lack of uniform theoretical frame and analytical method, a new SCM analytic design general framework is proposed in this paper. This framework is implemented to present a generalized spreading symbol waveform, and it creates the cross-correlation function between the binary offset carrier (BOC) signal and the local signal in receiver. It is confirmed with the mathematical theory based on practical methods. The theoretical analysis and simulation resuhs indicate that in the proposed SCM analytic design general framework and the existing methods based on the combination of correlation functions can be unified, and more importantly, the unambiguous acquisition and tracking algorithms for BOC signals can be designed under this framework. It provides an analytical tool for SCM. [ABSTRACT FROM AUTHOR]

Considering the characteristics of space projects and their resource scheduling problem, the models for the multi-project resource scheduling are given and an optimized scheduling method based on the genetic algorithm is proposed in the paper. A case study shows that the optimized resource scheduling method can be helpful for solving the multi-project scheduling problems in the space project development. The process and results show that the model and the method are better for solving the resource constraints and conflicts, and further support the project progress and the product quality. [ABSTRACT FROM AUTHOR]

A new algorithm based on S-transform is proposed for accurately and fast recognizing the pulsars' signals in this paper. It is verified by simulation results that the time-frequency distribution of pulsars' signal based on S-transform is basically invariant with different observed frequencies and signal-noise ratios. Based on these constant signatures, the minimum standardized Euclidean distance classifier is employed to classify pulsars' signals. Finally, the experimental results show that the proposed method has good noise immunity, higher recognition rate and fast processing speed. [ABSTRACT FROM AUTHOR]

A novel subspace tracking algorithm based on subspace distance is proposed in this paper. The proposed algorithm provides robust orthonormal vector estimation adapting to signal subspace and noise subspace. Simulation results demonstrate that the proposed algorithm is numerically stable, because it does not accumulate roundoff errors. Moreover, the proposed method performs well in subspace tracking and it has a low complexity of 3NL + O(N). [ABSTRACT FROM AUTHOR]

Attitude control instability occurs for reaction wheel failure in the phase of accurate attitude control of a space tethered robot. In order to solve this problem, a new attitude tolerant control method is proposed in the paper. A time-delay control algorithm is utilized to introduced previous one-step control information into the current control law, and the current changed control information is estimated and compensated. The stability of the tolerant control law is proved, and the time-delay control algorithm is compared with conventional proportional-derivative control algorithm from two eases of reaction wheel with failure and without failure. The simulation results show that the time-delay control method have high accuracy and robustness of tracking target attitude, and have high stability for controlling attitude of space tethered robot when a reaction wheel failure occurs. [ABSTRACT FROM AUTHOR]

Traditional identification algorithms for Duffing oscillator are mainly based on the transitions of phase diagram, and they need a large number of cumulative inputs to transform the system from chaos to the large-scale periodic state, and these limit their applications of Duffing oscillator. A new algorithm based on Kalman gain is proposed in the paper to predict state transitions of the Duffing oscillator before transitions in the phase diagram. By the establishing of Duffing state equations and setting the control condition of measurement equations, an improved form of Kalman gain can be obtained to effectively predict the state changes of the Duffing oscillator, experiments of harmonic signal detections show that the predictive algorithm can not only reduce at least 50% input points to identify the phase transitions of oscillator, but also the detection accuracy is obviously improved. [ABSTRACT FROM AUTHOR]

A method for detecting Tie Points (TPs) in interferometric synthetic aperture radar (InSAR) block based on EM (Expectation Maximization) algorithm is proposed in this paper. In this method the problem of TP detection is cast into maximum a posterior probability (MAP) estimation and maximum likelihood (ML) estimation by using a mixture model under missing data. This statistical framework also takes into account matching probabilities of the feature descriptors attached to interest points, and then the transformation matrix and point correspondences are simultaneously solved by using the EM algorithm. Experiments on SAR images of both same strip and adjacent strips validate this method respectively. [ABSTRACT FROM AUTHOR]

In this paper, a distributed adaptive cooperative tracking control algorithm 1s investigated for multispacecraft formation flight, in which a directed conununication topology is used to characterize the interaction among spacecrafts considering uncertainties of spacecraft moment of inertia and external disturbances. Specifically, for the error dynamics equations of spacecraft described by the Modified Rodriguez Parameters (MRP), a sliding surface including the relative attitude errors and absolute attitude errors is designed. Then, a nonregressor-based adaptive control approach is presented to deal with the model uncertainties and external disturbance such that all of spacecrafts in the formation converge to the desired attitude cooperatively. Finally, an illustrative example is conducted to demonstrate the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Autonomous navigation technique of Global Navigation Constellation presents a new high requirement for autonomous orbit prediction accuracy and computing speed. Combining the ground long-term orbit prediction accuracy and the performance of onboard computer, a sort of autonomous orbit prediction technique based on long-term navigation message uploaded from the ground is presented in this paper. The technique has two main features: Firstly, it can make full use of the high accuracy and high conciseness of navigation message uploaded from the ground, and gives consideration to both the high accuracy of reference ephemeris and save of onboard storage resources. Secondly the analytical solution algorithm of onboard state transition matrix can significantly save the amount of satellite-ground uplink data, onboard data storage and computational effort compared with the ground-uploaded and onboard-stored way. Computional resources, consumption of storage resources, and prediction accuracy are statistically analyzed by the simulation, and the results show that onboard autonomous orbit prediction using this technique occupies less computional resources, the computing speed is fast and prediction accuracy is high. The autonomous orbit prediction technique has important application value in autonomous navigation of global navigation satellite constellation. [ABSTRACT FROM AUTHOR]

Signals of interest (SOIs) extraction is a vital issue in the field of communication signal processing. In this paper, the cyclostationary property of communication signals is incorporated into the constrained ICA (cICA) framework to form a new constrained optimization problem. The approach incorporates cyclostationarity constraints in the ICA process to perform separation and selection of the SOIs simultaneously. Numerical simulations demonstrate the effectiveness and higher performance of the proposed algorithm compared with the conventional ICA algorithms such as FastICA. [ABSTRACT FROM AUTHOR]

An effective compression technique for hyperspectral images has become one of the focuses in the field of space hyperspectral remote sensing. The lossless compression technique of hyperspectral images based on distributed source coding (DSC) is studied in this paper. First, the theoretical foundation, realizable manner of DSC and its advantages in lossless compression of hyperspectral images are introduced. Then the research progress of lossless compression of hyperspectral images based on DSC is summarized, a distributed lossless compression algorithm of hyperspectral images based on multiband prediction is proposed. Experimental results show that the proposed algorithm has low encoding complexity, its compression performance is also better than that of the existing distributed compression algorithms. Finally, the problems which need further research on DSC application in hyperspectral images compression are pointed out. [ABSTRACT FROM AUTHOR]

The accuracy of the lunar UV sensor is limited by the oblate shape of the moon. The imaging principle of the lunar UV sensor and the geometry constraints when the sensor detecting the lunar horizon edge are investigated in this paper. Based on the imaging principle, a lunar nadir vector determination method is investigated. Compared with other approaches in previous literatures, the lunar oblateness is considered in this algorithm. Thereafter, a scenario of autonomous navigation for a lunar satellite based on orientation information of Sun-Moon-Earth is presented by using this algorithm to correct lunar oblateness. Simulation results show that the navigation position accuracy can achieve 300m(3σ) and velocity accuracy can achieve 0. 6m/s(3σ) under measurement noises of 0. 02°(3σ) for the sun sensor, 0. 05°(3σ) for the earth sensor, and 0.1°(3σ) for the moon sensor, and ensures navigation accuracy of lunar satellite. [ABSTRACT FROM AUTHOR]

For the problem of adaptive filtering in non-Gaussian alpha stable distribution noise environment, a variable step-size normalized least mean p norm (VSS-NLMP) algorithm with gradient-based weighted average is proposed. The Euclidean norm of the smoothed gradient vector, which can track the variation of the mean square deviation (MSD) at iteration, and fractional low order moments of the system error are used to update the step-size parameter in recursion. The weighted average of the gradient vector reduces the noise effectively. The update and convergence of the proposed algorithm are formulated in this paper. The simulation results indicate that the proposed algorithm has better performance compared to the existing VSS-NLMP algorithms. [ABSTRACT FROM AUTHOR]

Spatial smoothing is a common method of adaptive beamforming based on the coherent circular arrivals, but it loses the aperture of the array. In this paper, a new algorithm which uses the extended spatial smoothing method with full array weighted is proposed. First, the extended spatial smoothing method is exploited into beamforming for coherent noncircular signals, and its efficiency is proved in theory. Compared with the conventional spatial smoothing method, the number of the total signals (composed of the desired signal, the interferences and the background noise) is improved. Then, to decorrelate more efficiently, subarrays are weighted by the virtual beamforming. Finally, the subarray beamforming weight vector is extended to the full array beamforming weight vector by the transformation matrix. The full weighted method avoids the loss of aperture. Simulation results support the theoretical predictions. [ABSTRACT FROM AUTHOR]

Combined with sparse SIMO radar array in space domain, the two dimensional sparsity model for radar imaging with high resolution is established in this paper with frequency-stepped chirp signal (FSCS). First, a velocity estimation method for moving targets is introduced for this model based on image entropy criteria, and the accurate velocity estimation is implemented by simple zero-padding for low dimensional data. Second, in combination of the Compressed Sensing (CS) theory, the effective measurement matrix, the sparsity transform matrix and the reconstruction algorithm are designed to obtain the high-resolution range profile (HRRP), then a phase remain character based new imaging method is proposed for SIMO high-resolution sparse radar by two dimensional sparsity processing in the frequency and the space domains. The model can reduce not only the number of sub-pulses in FSCS burst, but also reduce the number of receivers of S1MO high-resolution radar, in the meanwhile, the high quality HRRP and two dimensional images of targets can be achieved. Effectiveness and robustness of the method are proved by the simulation results. [ABSTRACT FROM AUTHOR]

The pseudocode acquisition method based on iterative message passing algorithm (IMPA) is able to improve the acquisition speed greatly under the low complexity condition, but decrease fast in the poor SNR conditions. In the multiple input multiple output (MIMO) systems, it can weaken the multi-path fading, and improve the performance of the communication systems without increasing the spectrum resource and the transmit power. In this paper, the IMPA used in MIMO system is proposed, in which the diversity technique is adopted in the receiver side, the maximal ratio combining (MRC) method is used to combine the received signals, and then the IMPA is used to acquire the signals. Simulation indicate that the IMPA used in MIMO can improve the acquisition probability effectively without impacting acquisition speed, the acquisition probability can achieve 90% when SNR is -22dB, and the performance is better than the existing method. [ABSTRACT FROM AUTHOR]

SpaceWire is a newly developed serial link standard, and has been recommended as the next generation onboard data bus by ESA and NASA. One application of SpaceWire is to be used as the sole bus for the unified on-board communication infrastructure. As typical real-time systems, on-board networks usually have strict requirements for message transfer delay. However, the classical SpaceWire network is fundamentally multi-nodes, asynchronous and event-triggered, which is not designed to provide the guaranteed message transfer delay. This has become a bottleneck for its application in the unified on-board communication infrastructure. So a time-triggered communication protocol is proposed for SpaceWire on-board networks in this paper. In addition, the corresponding communication scheduling algorithm is devised. By reasonable planning, network nodes transmit communication data only in the allocated windows. This avoids network congestion caused by resource conflict, and the guaranteed message transfer delay is thus provided. [ABSTRACT FROM AUTHOR]

The global optimal 4-D trajectory (t, x, y, z) for a spacecraft controlled by low thrust and launched from the Earth to fly around the Sun is proposed in this paper. To optimize the 4-D trajectory of the spacecraft, a set of numerical algorithm, including a searching algorithm and a 4-D trajectory optimization algorithm is presented. The searching algorithm is used for finding as many as possible asteroids near the 4-D trajectory of the Earth chosen from all the 248997 asteroids in the whole Sun system. The performance index of optimal trajectory is to maximize the number of asteroids met with the spacecraft and the rendezvous times with them, and also maximize the final mass. The 4-D trajectory optimization algorithm is composed of improved dynamic programming algorithm, conjugate gradient algorithms based on optimal control theory and static parameter optimization algorithm. Based on a great deal of numerical flight simulation by using this combined algorithm, the 4-D optimal trajectory of the spacecraft is obtained, the spacecraft passes by 12 asteroids among the 248997 asteroids in the whole Sun system within one year. [ABSTRACT FROM AUTHOR]