Pingyuan Cui

Observability-Based Beacon Configuration Optimization for Mars Entry Navigation

In this paper, a novel observability analysis method of a nonlinear navigation system is proposed, and its application to the optimization of beacon configuration for Mars entry navigation is demonstrated. A Lie algebra-based approach to nonlinear observability is used to compute the observability matrix. The quadratic approximation to the Lie derivatives is then used to recursively calculate the observability matrix efficiently. Next, the inverse of the condition number of the observability matrix is chosen as a metric to evaluate the observability quality. To verify the accuracy and effectiveness of the proposed approach, Mars navigation scenarios with ranging measurements from multiple ground-based beacons are considered in simulation examples, and the optimal beacon configurations are obtained using a genetic algorithm. The extended Kalman filter is finally used to demonstrate the navigation performance. It is concluded that the proposed observability analysis method is able to optimize the beacon con...

Analysis of Two-Impulse Capture Trajectories into Halo Orbits of Sun–Mars System

T HE libration points of the three-body system attract many scientists because the libration points, natural equilibrium solutions of the circular restricted three-body problem (CRTBP), offer the unique possibility to have space astronomical observation [1] and low-energy interplanetary transfer [2–7]. Moreover, the libration points will be considered as a candidate location to establish a reusable and repetitive interplanetary cargo system or transportation system in the future [8–11]. When constructing a spaceport in the vicinity of libration points in a sun–planet system, the design and analysis of spacecraft escape and capture trajectories from or to halo orbits around the libration points, such as L1 or L2 point, is an important problem for interplanetary transportation systems and have been a topic of study. Recently, Nakamiya et al. [10,11] studied the escape and capture trajectories from or to halo orbits around the L1 or L2 points using impulsive maneuvers at periapsis of the manifolds for interplanetary transfers. In particular, a systematic analysis of capture trajectories to Lyapunov/halo orbits from interplanetary trajectories in the Hill three-body problem was carried out [10]. When searching the first four periapsis passage points of stable manifolds, the periapsis altitude of 200 km, with respect to Mars, was considered. It is known that these stable manifolds would play a key role in the searching process of capture trajectories. Moreover, in previous research, little attention has been given to some branches of stable manifolds that have only one opportunity of Mars flyby and periapsis altitude is larger than 200 km. These branches would provide some unique capture opportunities for interplanetary transfer missions. Therefore, the aim of this Note is to analyze the two-impulse capture trajectories into halo orbits of the sun–Mars system by adopting these discarded branches of stable manifolds. This Note is organized as follows. Section II briefly describes the problem. Section III defines the parameters of two-impulse capture trajectories and presents the numerical analysis method. Section IV applies our study of capture trajectories to halo orbits to a sun–Mars system. Some novel capture opportunities are found. II. Brief Description of the Problem

Real-time Navigation for Mars Final Approach Using X-ray Pulsars

An accurate knowledge of Mars entry condition is the significant requirement for the successful aerocapture and pinpoint landing. In order to develop the real-time navigation scheme for Mars final approach, the feasibility of navigation embedded X-ray pulsar observations is verified, and the navigation performance is comparatively analyzed. In order to choose optimal navigation pulsars from pulsar candidates, the Fisher information matrix is utilized to evaluate the observability from the estimation theory point of view. The optimal navigation pulsars thus are selected such that the determinant of the Fisher information matrix is maximal. Two navigation scenarios based on the 2012 encounter at Mars of Curiosity spacecraft combining with X-ray pulsar based measurements are then considered to demonstrate the navigation performance. Furthermore, a series of research on the error ellipse in Mars B-plane and the distribution of estimated flight path angle indicate that Xray pulsar based navigation, which may provide more accurate knowledge of Mars entry condition, is a potential navigation scheme for Mars final approach in the future.

Hazard detection and avoidance for planetary landing based on Lyapunov control method

Future planetary landers must be capable of detecting hazards in the landing zone and maneuvering to a new and safe site, for the requirements of the scientific task. This paper presents an autonomous hazard detection and avoidance method based on Lyapunov control method for planetary landing. The terrain of the landing zone is first reconstructed using the feature points of pictures at two different time, and the plane of the landing zone was determined by fitting the terrain elevation data. Then, hazards in the landing zone were identified according to the vitual plane. In order to reduce the potential threats by the hazards, an avoidance control law is designed using Lyapunov function method. The control law can guarantee the landers reach the safe site, simultaneously decrease the landing speed to zero. The results of numerical simulation show that the method is satisfactory for hazards detection and avoidance with assumed environments.

A rapid uncertainty propagation method for pre-parachute phase of Mars entry

In this paper, a novel approach is proposed for analyzing evolution of uncertainty in state trajectories of a Mars entry vehicle due to uncertainties in initial conditions and other system parameters. By introducing uncertainty factors, the stochastic dynamical systems are converted into equivalent deterministic dynamical systems in higher dimensional space. And then based on the local linearization and linear system theory, a rapid uncertainty propagation method can be get. Applying the method to a representative entry scenario taken from the NASA MSL-class mission, Simulation results indicate that the proposed method is able to predict evolution of uncertainty, compared with Monte Carlo method, with little degraded accuracy, but with much more computational efficiency.

Collaborative autonomous navigation in unknown environment

The main problems with autonomous navigation system that uses GPS is the satellite outages and the mapping of the ambience in unknown environment. Techniques was presented to increase position accuracy and navigation robustness in unknown environment by means of collaborative navigation. When vehicle one is navigating, lines of sight to satellites will often be blocked, however, vehicle two at different locations can have different sets of visible satellites and act as virtual satellite. Through collaboration, the satellite information can be shared between vehicles; then, better navigation performance will be achieved. At the same time, vehicle one can map its environment and locate itself accurately even when GPS signal is artificially broken. Simulation results indicate increased accuracy when using the method under investigation. Collaborative autonomous navigation can help several relatively simple vehicles achieve the same performance as expensive and complex platforms.

Sequence detection of planetary surface craters from DEM data

The research on identification and recognition of impact craters on planetary surface is focused on how to detect them from background. A novel sequence algorithm is proposed to crater detection that utilizes DEM data instead of images. By investigating the features of ideal craters, several constraints can be developed to extract candidate crater edges from other topographies. Based on the fact that the shape of most craters is approximate to an ellipse, the Least Median Square Ellipse Fitting Method can be used to exclude pseudo-edges, and to reserve the real edges which contain the feature of the crater. The location, orientation and other physical parameters of the crater can be determined by fitting real edges to an ellipse based on Robust Least Square Method. Mathematical simulations are performed with the moon DEM data. The results show that the topography-based crater detection algorithm offers an effective method for identification and characterization of ellipse-like impact craters, and the accuracy is high enough.

Research on optical/inertial integrated navigation for soft landing on asteroids using mixed H 2 /H ∞ filter

Divergence of traditional Kalman filtering will happen while observation or system noise does not accorded with hypothesis and H<inf>∞</inf> filtering has not enough precision although robustness, so the popular style is the mixed H<inf>2</inf>/H<inf>∞</inf> filtering. Aiming at the problem, this paper puts forward a kind of filtering way which mixes filtering mode using a weighted combination of the H<inf>2</inf> and H<inf>∞</inf> gains without creating model for noise, and applies the algorithm to the optical/inertial integrated navigation system. The simulation results indicate that the optical/inertial integrated navigation system for soft landing on asteroids using the mixed H<inf>2</inf>/H<inf>∞</inf> filter improves the robustness as guaranteeing the enough precision of the navigation system.

Optimal-fuel, low-thrust Earth-Ivar transfer trajectories with Venus gravity assist

In this paper, fuel-optimal low-thrust trajectory with Venus gravity-assist is presented for exploring Ivar asteroid. The problem formulation treats the spacecraft mass as a state variable, thus coupling the spacecraft design to the trajectory optimization. To avoid numerical sensitivity, the equinoctial elements are utilized to describe spacecraft motion, and the optimization problem is divided into three subproblems, the solution of the last subproblem is taken as the primary guess for the next one. A hybrid optimization method is utilized to solve them, which method utilizes the costate time histories to parameterize the thrust steering angles time histories. Numerical results are presented for the optimal three-dimensional Earth-Ivar with Venus gravity-assist trajectory

The Nereus Asteroid Rendezvous Mission design with multi-objective hybrid optimization

As one of the potential candidates of the Asteroid Exploration Mission to be launched around 2010, we investigated the feasible mission scenarios. Firstly, according to goal and constraints of the mission, the opportunity for asteroid exploration mission is analyzed. The 4660 Nereus is selected as the candidate. We searched and presented the optimal rendezvous opportunity for 4660 Nereus from 2009 to 2010. Through analyzing the direct transfer trajectory, unexpected result that the trajectory would pass the 12866 asteroid and 7080 asteroid is found. Then, we calculated and optimized the new profile with multiple flybys by using the hybrid search algorithm combining the genetic algorithm with sequential quadratic programming method. Finally, we analyzed the trajectory characteristics and gave some key parameters, which would have a direct impact on communication system, power system, thermal control system of spacecraft, and so on