Earth–Moon low energy trajectory optimization in the real system

The problem of the Earth–Moon low energy trajectory optimization in the real system (the model defined by the JPL ephemeris DE405) is considered in this paper. First, this problem is investigated in the model of circular restricted three-body problem, since the fuel consumption is closely related to the Jacobi integral of the transfer trajectory, a method based on Jacobi integral is proposed and eight optimal trajectories are obtained. These optimal trajectories provide initial information (the flight time and the braking velocity impulse) to search the optimal low energy trajectories in the real system through optimization techniques. Considering the merit and drawback of particle swarm optimization and differential evolution algorithm in solving the space trajectory problem, an improved cooperative evolutionary algorithm is put forward. Result shows that the low energy trajectories in the real system are more fuel-efficient than the corresponding ones under the circular restricted three-body problem.     

Multiobjective genetic optimization of Earth–Moon trajectories in the restricted four-body problem

In this paper, optimal trajectories of a spacecraft traveling from Earth to Moon using impulsive maneuvers (ΔV maneuvers) are investigated. The total flight time and the summation of impulsive maneuvers ΔV are the objective functions to be minimized. The main celestial bodies influencing the motion of the spacecraft in this journey are Sun, Earth and Moon. Therefore, a three-dimensional restricted four-body problem (R4BP) model is utilized to represent the motion of the spacecraft in the gravitational field of these celestial bodies. The total ΔV of the maneuvers is minimized by eliminating the ΔV required for capturing the spacecraft by Moon. In this regard, only a mid-course impulsive maneuver is utilized for Moon ballistic capture. To achieve such trajectories, the optimization problem is parameterized with respect to the orbital elements of the ballistic capture orbits around Moon, the arrival date and a mid-course maneuver time. The equations of motion are solved backward in time with three impulsive maneuvers up to a specified low Earth parking orbit. The results show high potential and capability of this type of parameterization in finding several Pareto-optimal trajectories. Using the non-dominated sorting genetic algorithm with crowding distance sorting (NSGA-II) for the resulting multiobjective optimization problem, several trajectories are discovered. The resulting trajectories of the presented scheme permit alternative trade-off studies by designers incorporating higher level information and mission priorities.     

Meteoroid and Space Debris Risk Assessment for Satellites Orbiting the Earth/Moon

Interplanetary meteoroids and space debris can impact satellites orbiting the Earth or spacecraft traveling to the Moon. Targeting China Space Station(CSS), 7 satellites selected from the constellation of Beidou Navigation Satellite System Phase Ⅲ(BDS-3), and 3 spacecraft orbiting the Moon, we have adopted in the paper the Meteoroid Engineering Model 3, Divine-Staubach meteoroid environment model, and Jenniskens-Mc Bride meteoroid steam model to analyze the meteoroid environment with the mass ra...     

Two-manoeuvres transfers between LEOs and Lissajous orbits in the Earth–Moon system

The purpose of this work is to compute transfer trajectories from a given Low Earth Orbit (LEO) to a nominal Lissajous quasi-periodic orbit either around the point L₁ or the point L₂ in the Earth–Moon system. This is achieved by adopting the Circular Restricted Three-Body Problem (CR3BP) as force model and applying the tools of Dynamical Systems Theory.     

Wireless Sensor Networks – A potential tool to probe for water on Moon

A Wireless Sensor Network for in situ probing of lunar water/ice is proposed. The mission scenario in single and multi-tier architectures for probing water in a permanently shadowed region of the Moon and different scenarios of exploration are discussed. The ideas presented in the paper are a positive assertion of feasibility for the sensor node hardware, given current levels of technological advancements.     

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美国航空航天局“轨道碳观测”（OCO）卫星将于2009年年初由“金牛座”火箭发射 该卫星采用低地球轨道星（LEO Star）平台，     

Alternative transfer to the Earth–Moon Lagrangian points L4 and L5 using lunar gravity assist

Lagrangian points L4 and L5 lie at 60° ahead of and behind the Moon in its orbit with respect to the Earth. Each one of them is a third point of an equilateral triangle with the base of the line defined by those two bodies. These Lagrangian points are stable for the Earth–Moon mass ratio. As so, these Lagrangian points represent remarkable positions to host astronomical observatories or space stations. However, this same distance characteristic may be a challenge for periodic servicing mission. This paper studies elliptic trajectories from an Earth circular parking orbit to reach the Moon’s sphere of influence and apply a swing-by maneuver in order to re-direct the path of a spacecraft to a vicinity of the Lagrangian points L4 and L5. Once the geocentric transfer orbit and the initial impulsive thrust have been determined, the goal is to establish the angle at which the geocentric trajectory crosses the lunar sphere of influence in such a way that when the spacecraft leaves the Moon’s gravitational field, its trajectory and velocity with respect to the Earth change in order to the spacecraft arrives at L4 and L5. In this work, the planar Circular Restricted Three Body Problem approximation is used and in order to avoid solving a two boundary problem, the patched-conic approximation is considered.     

航天·水·生命·健康——北京华美倚兰科技发展有限公司

水是生命的源泉,而现代社会水资源的污染,严重吞噬着人类的健康,人们怎么也没有想到,和我们的生活息息相关并始终不渝支撑我们的生命之水,竟然会有直接威胁人类生存的一天。     

合作成就未来——访欧空局局长让·雅克·多尔丹

在世界月球会议开幕式的午宴后，我们有幸采访了欧空局局长让·雅克·多尔丹。让·雅克·多尔丹局长的健谈和对国际合作的丰富经验及热切渴望让我们印象深刻。这已经是他第十次来中国了，问及他对中国的印象，他说：“中国给我留下了极深的印象，中国的太空计划令人记忆深刻!”同时他对中国航天界的工作成果也给予了很高的评价：中国在太空领域是一个大国，在太空发展计划、地球探测及定位、航空航天、载人飞行等方面做得很好，并且努力地拓展项目的外延。     

首枚"织女星"运载火箭即将发射

在欧洲航天局（ESA）7个成员国（意大利、法国、比利时、瑞士、西班牙，荷兰和瑞典）的支持下，“织女星”（VEGA）运载火箭从1988年开始研制，用于发射政府和商用小型有效载荷，这种四级火箭能将1500kg的有效载荷发射到700km高的轨道上，     

欧洲"伽利略"卫星导航系统概况

“伽利略”（Galileo）卫星导航系统是欧洲正在实施的一项重大民用航天项目，于20世纪90年代由欧洲委员会和欧洲航天局共同发起，其目标是建成欧洲自主的民用全球卫星导航系统，并与美国“全球定位系统”（GPS）和俄罗斯“全球导航卫星系统”（GLONASS）相兼容，从而摆脱对GPS的依籁。打破美国对全球卫星导航定位产业的垄断。在使欧洲获得工业和商业效益的同时，为建立欧洲共同安全防务体系提供基础条件。     

福克·沃尔夫的“猫头鹰”

漂亮的飞机往往可以选题以大家的欣赏，但有时一些外形狰狞怪诞、带有异国风味且性能优越的飞机更能够吸引飞行员的目光，他们会在心中揣摩着自己驾驶它的感受-这也许是人类好奇的天性使然。德国福克·沃尔夫公司生产的Fw189“空中眼睛”侦察／攻击机，虽然缺乏强劲的动力，亦无德国飞机普通具有的流畅外表，布局上更偏离了主流设计，但却是很多飞行员憧憬并且最终成为爱不释手的飞机之一。     

"混合控制"驱动虚拟人实现维修仿真

目前在开展虚拟维修仿真过程中,驱动虚拟人多采用2种方式,一种为沉浸式的虚拟外设控制,另一种为非沉浸式的算法控制.2种方式各有其局限性,为了提高维修仿真的实现效率,提出混合控制的方法及实现结构,即在算法控制虚拟人的仿真过程中插入虚拟外设控制方式,目的在于充分利用这2种控制方法的长处.对混合控制系统结构进行了描述,分析了2种控制方式之间的转换机制,并用实例加以验证.在当前的软硬件技术条件下混合控制方法为实现维修仿真提供了有效的技术手段.     

“ 互联网+” 计量发展现状与建议

分析了国内计量检测行业现状与存在的问题,描述了“互联网+”计量服务模式的初步探索情况,指出“互联网+”计量转型是未来计量检测领域的必然发展趋势,提出了“树立正确的互联网思维、加强对“互联网+”计量模式的研究与应用, 加强行业整合、提高为用户服务能力”的措施及建议。     

Zero,minimum and maximum relative radial acceleration for planar formation flight dynamics near triangular libration points in the Earth–Moon system

Assume a constellation of satellites is flying near a given nominal trajectory around _L4$L_4$ or _L5$L_5$ in the Earth–Moon system in such a way that there is some freedom in the selection of the geometry of the constellation. We are interested in avoiding large variations of the mutual distances between spacecraft. In this case, the existence of regions of zero and minimum relative radial acceleration with respect to the nominal trajectory will prevent from the expansion or contraction of the constellation. In the other case, the existence of regions of maximum relative radial acceleration with respect to the nominal trajectory will produce a larger expansion and contraction of the constellation. The goal of this paper is to study these regions in the scenario of the Circular Restricted Three Body Problem by means of a linearization of the equations of motion relative to the periodic orbits around _L4$L_4$ or _L5$L_5$. This study corresponds to a preliminar planar formation flight dynamics about triangular libration points in the Earth–Moon system. Additionally, the cost estimate to maintain the constellation in the regions of zero and minimum relative radial acceleration or keeping a rigid configuration is computed with the use of the residual acceleration concept. At the end, the results are compared with the dynamical behavior of the deviation of the constellation from a periodic orbit.     

54两次访问月球的约翰·扬

“阿波罗”16号登月航天员约翰·扬，是美国航天史上航天员生涯最长、执行任务最多的航天员之一，也是一位颇有传奇色彩的航天员：他曾经六次进入太空，两次去过月球（一次为绕月，一次为登月）。人称约翰·扬工作、睡觉、吃饭、呼吸均与太空飞行息息相关。     

西班牙海军 世界首艘“宙斯盾”护卫舰“阿尔瓦罗·德·巴赞”号导弹护卫舰

西班牙的“阿尔瓦罗·德·巴赞”（Alvaro de Bazan，亦称F100）级护卫舰是一艘多功能护卫舰，一艘为处理危险状况，能为远征部队提供保护且在海上作战时作为旗舰指挥作战的理想水面舰艇。F100级护卫舰在担任海上特遣舰队的旗舰时，除取有进行空中作战信息整合、指挥舰队进行防空作战之外，也能担任反潜作战指挥平台。虽然在今日海军中反潜已经不是水面舰艇最重要的任务，但是，西班牙海军的“阿尔瓦罗·德·巴赞”号护卫舰还是配置了高科技的反潜作战系统，并在未来的作业中证明其价值。     

美国新发射的"圣杯"月球探测器简介

2011年9月10日,美国成功发射＂圣杯＂（GRAIL,又名＂重力恢复与内部实验室＂）探测器,其主要任务是探测月球重力场和内部结构。GRAIL包括两个相同的月球探测器,分别为GRAIL-A和B,它们运行在50km的近圆形月球极轨道上,利用Ka频段在两个探测器之间进行高精度距离变化率测量,通过对这些测量数据的分析,能直接获得月球重力场分布的信息。GRAIL的任务时间为270天,其中90天进行月球重力场测绘。