Search

To solve the problems of possible real-time trajectory correcting and landing site re-designating during Mars powered descent, the paper computes the reachability set at the beginning of the powered descent phase offline and determines the final landing site online by comparing the current state of the lander with the obtained reachability set. The corresponding descent trajectory is then rapidly searched. If the lander fails to reach any of the given targets, a new landing site in the field of view will be selected through safety index and a trajectory will be planned. The simulation result shows that the proposed reachability set-based rapid trajectory planning method manages to determine the final landing site and obtain the landing trajectory in real-time according to the practical initial state of the lander, fulfilling the goal of Mars soft landing with limited fuel consumption. [ABSTRACT FROM AUTHOR]

In this paper, the multi-objective optimization of Halo-to-Halo transfer trajectory between different Sun- planet systems is discussed by considering the ephemeris constraints. The direct and indirect transfers that employ the different sets of the invariant manifolds are analyzed, respectively. The pseudo-manifolds, along which the spacecraft can depart and approach Halo orbit quickly, is introduced to replace the traditional invariant manifolds. Then, the multi-objective optimization models are built for two transfer schemes. In the direct transfer scheme, the outer branches of the pseudo-manifolds are connected under the heliocentric two-body model. In the indirect transfer, the inner branches of the pseudo-manifolds and the interplanetary transfer trajectory are connected by combining the periapsis Poincare map with a matching algorithm. Further, a polynomial spline method is utilized to estimate the pseudo-manifolds. The computational efficiency is improved for avoiding the numerical integration. For each transfer scheme, the trajectory design can be considered as a multi-variable unconstrained optimization problem. The NSGA-II (Non-domination Sort Genetic Algorithm) is adopted to solve the problems taking total velocity increment and flying time as optimization objects. The efficiency of the proposed approach is verified by the simulation example of Earth-Mars Halo-to-Halo transfer trajectory. [ABSTRACT FROM AUTHOR]

Mars Science Laboratory (MSL) has successfully landed Curiosity rover on Mars, and this creates a new situation for Mars precision landing. Taking the MSL mission for example, the guidance scheme and its development trend of entry, descent and landing on Mars are analyzed in this paper. In order to land Martian rovers on high elevation regions and hazardous regions, several primary problems that the guidance system is faced with are summarized. And based on the need of the autonomous and adaptive technique development and the problems that the guidance system is faced with, key techniques of guidance aspect for future Mars landing mission are presented, and also, the potential of the related techniques for applying to the practical engineering is prospected. [ABSTRACT FROM AUTHOR]

Based on the future Chinese Mars mission, firstly a brief review of previous successful Mars landing is given. Followed by above, the cause of blackout and its relationship with communication are analyzed. In order to solve the communication blackout problems, some key techniques with their research progress are summarized. Finally, some proposals for the future Chinese exploration of Mars are presented. [ABSTRACT FROM AUTHOR]

Aiming at planning the vehicle's entry trajectory for Mars Pin-Point Landing, a new method based on hp-Radau pseudospectral algorithm is proposed. The vehicle's dynamics, state constraints during Mars Entry phase and vehicle' s mobility and safety constraints are taken into consideration synthetically. By combining the properties of collocation points of hp-Radau pseudospectral algorithm, the problem of trajectory optimization can be converted into a large-scale parameters optimization problem with multi-constraints, thus a solving framework of trajectory optimization is obtained. Also, the analytical form of Jacbian matrix of performance index and constraint equations is derived in order to improve the method's efficiency. The simulation result indicates that; (1) the hp-Radau pseudospectral algorithm can be used to solve the trajectory optimization problem during Mars Entry ,and has more efficient performance compared with the radau pseudospectral algorithm; (2) Compared with the numeric difference method, the analytical form of Jacbian matrix could substantially increase the method's efficiency and time-consuming stability by 58.75% and 85.58% respectively. [ABSTRACT FROM AUTHOR]

Focusing on the successful Mars landing exploration missions and developing demand for Mars landing exploration missions in the future, the necessity and importance of autonomous navigation for Mare entry phase are elaborated. First, state-of-the-art techniques and research tendency of autonomous navigation for Mars entry phase are summarized. Then the characteristics and challenges encountered are analyzed, and key techniques involved are discussed synthetically. Finally, the development direction of Chinese Mare entry navigation technique for future Mars exploration missions is previewed. [ABSTRACT FROM AUTHOR]

A relative navigation method using a camera and a three-beam ranger is developed to address the challenge of scarce of natural mark for absolute navigation. The camera is used to measure the coordinates of the random features in the photo plane, while the three-beam ranger is used to obtain the normal vector of the landing plane. Combining these two kinds of the measurements, the relative navigation reference system is established and the position of each feature in this reference system is obtained. Exploiting the features with known positions, the navigation system is designed to estimate the lander's position, velocity and attitude in the relative navigation system. Afterwards, the observability analysis is performed based on the observability matrix to reveal the least amount of features to satisfy the observability. Finally, the numerical simulations are performed to analyze the state estimation accuracy and validate the observability analysis. The proposed method needs no Martian terrain database, and realizes the high-precision full-state estimation and meets the requirements of Mars high-precision soft landing. [ABSTRACT FROM AUTHOR]

Considering the numeric constraints, a planning approach based on a domain independent heuristic approach is proposed, and the heuristic is abstracted from the planning activity relevancy. The relevancy between activities is defined, and a dynamic self-learning updating process is given. The heuristic is designed based on the relevancy, guiding the activity selecting in the planning process, and the heuristic planning algorithm is finally proposed. The simulation results show that the algorithm can efficiently reduce planning steps and backtracking steps and improve the planning efficiency for deep space explorer. [ABSTRACT FROM AUTHOR]

Aiming at the Mars Pinpoint landing problem, a rapid trajectory optimization method with minimum fuel consumption during power descent phase is presented. Firstly, a trajectory optimization model with minimum fuel for Mars power descent phase is established; Secondly, the relationship between thrust magnitude and direction and costate variables is analyzed based on the maximum principle, and a conclusion that the lander should work at max or min thrust magnitude and the thrust direction should be in the direction of the costate vectors corresponding to the velocity states is obtained, on the basis of the conclusion the state and costate differential equations are converted to corresponding piecewise functions with constant thrust. Then, the analytical formulas of the piecewise functions are derived when the terminal time is given. Further, the algorithm flow chart of trajectory optimization for Mars powed descent phase is given. And last, mathematical simulation is conducted to compare the method to convex optimization method and polynomial method. Results show that the proposed method avoids the flaws of polynomial method and has more computational efficiency than convex optimization method. [ABSTRACT FROM AUTHOR]

Considering the limited resource, complex constraint and parallel activities, autonomous planning of spacecraft mission is investigated in this paper. A method for calculating the spacecraft resource based on the temporal topological sort is proposed. In consideration of resource production and consumption in the planning result, a resource constraint network model is introduced to express resource requirement for each activity. According to the analysis of the relations between resource changes and activity executing time, the resource mutation time of the resource constraint network is topologically sorted in the resource processing. The selection process of flow pushing path is optimized, and the time complexity is O(n²). Finally, the numerical simulation result shows that the algorithm improves the efficiency of resource processing. [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]

Searching launch opportunity of asteroid exploration escaped from Moon needs to take into account the gravity of Earth, Sun and Moon, A step by step and asymptotic method is proposed to search the launch opportunity for the multi-body dynamics model. In this method, the launch opportunity of transfer from Earth-Moon system to asteroid is searched in two-body dynamics model. The Earth-Moon motion is investigated to deduce the criterion of opportunities escaped from lunar orbit's tangent, and then the criterion and the contour map method are used to search launch opportunities. In order to improve the convergence of launch opportunity correction in multi-body dynamics model, an asymptotic correction strategy is adopted to correct the launch opportunity in Sun-Earth system and Sun-Earth-Moon system based on lunar escape orbit parameters as terminal constraints. The effectiveness of the proposed approach is demonstrated through the launch opportunities search of asteroids (3908) Nyx and (190491) 2000 FJ20 flyby missions escaped from Moon. [ABSTRACT FROM AUTHOR]

An autonomous crater detection method based on the image gray value feature is proposed in this paper. In this method, region of interest (ROI) is used to identify crater's edge distribution from real planet landing navigation images conveniently, thus avoiding dependence of image on solar elevation. Then an algorithm for determining both vehicle attitude and position by use of the nonlinear predictive filter is also described. Considering that landing terrain plays a significant role in celestial body landing navigation, a method of terrain map simulation is proposed. By sorting surface points into levels, new points completely depend on their higher-level neighbors according to the fractal theory. A celestial body random terrain map modeling method is proposed. Finally the paper presents the validation of the algorithms in the end. [ABSTRACT FROM AUTHOR]

The paper focuses on the feature detection and recognition on planetary surface in the deep space exploration mission. A novel detection and recognition method for irregular craters, especially overlapped and incomplete, craters on planetary surface is proposed. First, extraction of candidate crater edge is performed by using the Contextual-based Hopfield neural network. Furthermore, pseudo-edges which do not satisfy the constraints are removed by analyzing multi constraints for real crater edges. Finally, real edges containing the feature of the crater are detected by using the least median square ellipse fitting method combined with a robust least square method. Meanwhile the physical parameters are determined. Mathematical simulations demonstrate the performance of the proposed method for detection and recognition of irregular craters in complex background. [ABSTRACT FROM AUTHOR]