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A particle-linkage model for non-axisymmetric elongated asteroids

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Research in Astronomy and Astrophysics 2018年第7期18卷 101-112页

作者： Hong-Wei Yang Shuang Li Cong Xu College of Astronautics Nanjing University of Aeronautics and Astronautics Advanced Space Technology Laboratory Nanjing University of Aeronautics and Astronautics College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics

This paper investigates a simplified model for describing the gravitational fields of non- axisymmetric elongated asteroids. The connection between the simplified model and the target aster-oid is built by considering the positions of equilibrium points. To improve the performance of po-sition matching for the equilibrium points associated with these non-axisymmetric asteroids, a non-axisymmetric triple-particle-linkage model is proposed based on two existing axisymmetric particle- linkage models. The unknown parameters of the simplified model are determined by minimizing the matching error using the nonlinear optimization method. The proposed simplified model is applied for three realistic elongated asteroids, 243 Ida, 433 Eros and （8567） 1996 HW1. The simulation re-sults verify that the current particle-linkage model has better matching accuracy than the two existing particle-linkage models. The comparison, between the simplified model and the polyhedral model, on the topological cases of the equilibrium points and the distribution of gravitational potential further validate the rationality and accuracy of the simplified model.

关键词： asteroids individual （243 Ida 433 Eros （8567） 1996 HW1） - celestial mechanics -gravitation

Generating Periodic Orbits for Explorations of Elongated asteroids

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Journal of Beijing Institute of Technology 2020年第1期29卷 129-138页

作者： Huihui Wang Yuntao Jiang Long Xiao Yonglong Zhang Beijing Aerospace Automatic Control Institute Beijing 100854China National Key Laboratory of Science and Technology on Aerospace Intelligence Control Beijing 100854China School of Aerospace Engineering Tsinghua UniversityBeijing 100084China

A practical method is proposed to search for periodic orbits of elongated asteroids.The method obtains required initial variables of periodic orbits by using the rotating mass dipole with appropriate parameters,and then implement local iterations to obtain the real orbits over an asteroid in the polyhedral model.In this paper the dipole and polyhedral models,and list detailed procedures of the searching method are introduced.A planar single lobe orbit is presented to evaluate the effectiveness of the method,with the asteroid 216 Kleopatra of the triple asteroid system as a representative elongated body.By applying the above method,ten families of periodic orbits around Kleopatra are identified and discussed with respect to their orbital stabilities and periods.One sample of the sombrero orbit is checked by calculating 1000 hours to examine its orbital behavior.Besides the above orbits,the intriguing head-surrounding orbit is also analyzed.

关键词： periodic orbits elongated asteroids dipole model numerical iteration

Convex optimization of asteroid landing trajectories driven by solar radiation pressure

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Chinese Journal of Aeronautics 2022年第12期35卷 200-211页

作者： Chuanjun DONG Hongwei YANG Shuang LI Bo LI College of Astronautics Nanjing University of Aeronautics and AstronauticsNanjing 211106China Tianjin Key Laboratory of Microgravity and Hypogravity Environment Simulation Technology Tianjin 300458China Tianjin Institute of Aerospace Mechanical and Electrical Equipment Tianjin 300458China

High-area/mass ratio landers driven by Solar Radiation Pressure(SRP)have potential applications for future asteroid landing missions.This paper develops a new convex optimization-based method for planning trajectories driven by SRP.A Minimum Landing Error(MLE)control problem is formulated to enable planning SRP-controlled trajectories with different flight times.It is transformed into Second Order Cone Programming(SOCP)successfully by a series of different convexification technologies.A trust region constraint and a modified MLE objective function are used to guarantee the convergence performance of the optimization algorithm.Thereafter,the SRP-driven trajectory optimal control problem is converted equivalently into a sequence of convex optimal control problems that can be solved effectively.A set of numerical simulation results has verified the effectiveness and feasibility of the proposed optimization method.

关键词： asteroids Convex optimization Optimal control Soft landing Solar radiation pressure Trajectory optimization

Dynamic Problems of the Planets and asteroids, and Their Discussion

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International Journal of Astronomy and Astrophysics 2012年第3期2卷 129-155页

作者： Joseph J. Smulsky Yaroslav J. Smulsky Institute of the Earth’s Cryosphere Siberian Branch of Russian Academy of Sciences Tyumen Russia Institute of Thermophysics of Russian Academy of Sciences Siberian Branch Novosibirsk Russia

The problems of dynamics of celestial bodies are considered which in the literature are explained by instability and randomness of movements. The dynamics of planets orbits on an interval 100 million years was investigated by new numerical method and its stability is established. The same method is used for computing movements of two asteroids Apophis and 1950DA. The evolution of their movement on an interval of 1000 is investigated. The moments of their closest passages at the Earth are defined. The different ways of transformation of asteroids trajectories into orbits of the Earth’s satellites are considered. The problems of interest are discussed from the different points of view.

关键词： Dynamics Planets asteroids Satellites Stability Discussion

Simultaneous estimation of spacecraft position and asteroid diameter during final approach of Hayabusa2 to Ryugu

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Astrodynamics 2020年第2期4卷 163-175页

作者： Yuki Takao Yuya Mimasu Yuichi Tsuda Institute of Space and Astronautical Science Japan Aerospace Exploration AgencySagamihara252-5210Japan

This paper presents the optical navigation results of the asteroid explorer Hayabusa2 during the final rendezvous approach phase with the asteroid Ryugu.The orbit determination of Hayabusa2 during the cruising phase uses a triangulation-based method that estimates the probe and asteroid orbits using the directions from which they are observed.Conversely,the asteroid size is available as optical information just prior to arrival.The size information allows us to estimate the relative distance between the probe and the asteroid with high accuracy,that is strongly related to the success or failure of the rendezvous.In this study,the relative distance and asteroid size in real space are simultaneously estimated in real time by focusing on the rate of change of the asteroid size observed in sequential images.The real-time estimation results coincided with those of precise analyses performed after arrival.

关键词： asteroids small bodies optical navigation size estimation orbit determination real time

Comparison of three filters in asteroid-based autonomous navigation

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Research in Astronomy and Astrophysics 2014年第3期14卷 329-344页

作者： Wen Cui Kai-Jian Zhu State Key Laboratory of Astronautic Dynamics Xi’an Satellite Control Center

At present, optical autonomous navigation has become a key technologyin deep space exploration programs. Recent studies focus on the problem of orbit de-termination using autonomous navigation, and the choice of filter is one of the mainissues. To prepare for a possible exploration mission to Mars, the primary emphasisof this paper is to evaluate the capability of three filters, the extended Kalman filter（EKF）, unscented Kalman filter （UKF） and weighted least-squares （WLS） algorithm,which have different initial states during the cruise phase. One initial state is assumedto have high accuracy with the support of ground tracking when autonomous navi-gation is operating; for the other state, errors are set to be large without this support.In addition, the method of selecting asteroids that can be used for navigation fromknown lists of asteroids to form a sequence is also presented in this study. The simula-tion results show that WLS and UKF should be the first choice for optical autonomousnavigation during the cruise phase to Mars.

关键词： celestial mechanics asteroids equation of state methods: data analysis techniques: image processing

Study of photometric phase curve:assuming a cellinoid ellipsoid shape for asteroid(106)Dione

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Research in Astronomy and Astrophysics 2017年第9期17卷 61-70页

作者： Yi-Bo Wang Xiao-Bin Wang Donald E Pray Ao Wang Yunnan Observatories Chinese Academy of SciencesKunming 650216China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100012China Sugarloaf Mountain Observatory South DeerfieldMA 01373USA

We carried out new photometric observations of asteroid （106） Dione at three apparitions （2004, 2012 and 2015） to understand its basic physical properties. Based on a new brightness model, new photometric observational data and published data of （106） Dione were analyzed to characterize the morphology of Dione＇s photometric phase curve. In this brightness model, a cellinoid ellipsoid shape and three-parameter （H, G1, G2） magnitude phase function system were involved. Such a model can not only solve the phase function system parameters of （106） Dione by considering an asymmetric shape of an asteroid, but also can be applied to more asteroids, especially those without enough photometric data to solve the convex shape. Using a Markov Chain Monte Carlo （MCMC） method, Dione＇s absolute magnitude of H = 7.66＋0.03-0.03 mag, and phase function parameters G1 = 0.682＋0.077-0.077 and G2 = 0.081＋0.042-0.042 were obtained. Simultaneously, Dione＇s simplistic shape, orientation of pole and rotation period were also determined preliminarily.

关键词： asteroids general photometric phase curve -- asteroids individual （106） Dione - techniques： photometric - Markov Chain Monte Carlo method

Equilibrium points and orbits around asteroid with the full gravitational potential caused by the 3D irregular shape

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Astrodynamics 2018年第4期2卷 361-373页

作者： Yu Jiang State Key Laboratory of Astronautic Dynamics Xi’an Satellite Control CenterXi’an710043China School of Aerospace Engineering Tsinghua UniversityBeijing100084China

We investigate the equilibrium points and orbits around asteroid 1333 Cevenola by considering the full gravitational potential caused by the 3D irregular shape.The gravitational potential and effective potential of asteroid 1333 Cevenola are calculated.The zero-velocity curves for a massless particle orbiting in the gravitational environment have been discussed.The linearized dynamic equation,the characteristic equation,and the conserved quantity of the equilibria for the large-size-ratio binary asteroid system have been derived.It is found that there are totally five equilibrium points close to 1333 Cevenola.The topological cases of the outside equilibrium points have a staggered distribution.The simulation of orbits in the full gravitational potential caused by the 3D irregular shape of 1333 Cevenola shows that the moonlet’s orbit is more likely to be stable if the orbit inclination is small.

关键词： equilibrium points orbits polyhedral model asteroids 1333 Cevenola

Diversity and frequency of Nocardia spp.in the soil of Isfahan province,Iran

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Asian Pacific Journal of Tropical Biomedicine 2012年第6期2卷 474-478页

作者： Kachuei R Emami M Mirnejad R Khoobdel M Molecular Biology Research Center Baqiyatallah University of Medical Sciences Department of Medical Parasitology and Mycology Faculty of Public Health Tehran University of Medial Sciences Health Research Center Baqiyatallah University of Medical Sciences

Objective:To isolate and identify Nocardiaspp. from soil in different regions of Isfahan province in the center of Iran.Methods:This study was conducted in 32 districts(16 cities and 16 villages)in Isfahan province during two years. A total of 800 soil samples from these regions were studied by using kanamycin. The isolated Nocardiaspecies were examined by gram and acid-fast staining and were identified biochemically and morphologically. The frequency and distribution of Nocardia spp. were determined in relation to different factors such as soil pH and temperate climate.Results:From 153(19.1%)Nocardiaisolates identified,Nocardia asteroids(N. asteroids)complex(45.5%) andNocardia brasiliensis(N. brasiliensis)(24.7%) were the most frequently isolated species, followed by Nocardia otitidiscaviarum (2.2%),Nocardiopsis dassonvillei,Actinom adura actinomadura(each 1.7%) and Nocardia transvalensis(1.1%) and also unknown spp.(23.0%). In this study, most species(54.4%) of Nocardia, especially N. asteroides complex were isolated fromsoils with pH: 7.01-8, whereas in pH: 8.01-9 more N. brasiliensis was isolated. The most Nocardia spp. was detected from regions with semi-nomadic and temperate climate(41.1%).Conclusions:N. asteroids complex is more prevalent in Isfahan province and soil can be a potential source of nocardiosis infections. It is to be considering that climate and soil pH are involved in the frequency and diversity of aerobic Actinomy cetes.

关键词： Nocardia Nocardiosis Actinomycetes Soil microbiology Isfahan Iran Nocardia asteroids Climate