Determination of an instantaneous Laplace plane for Mercury’s rotation

Mercury is the target of two space missions: MESSENGER, which carried out its first and second flybys of Mercury on January 14, 2008 and October 6, 2008, and the ESA/JAXA space mission BepiColombo, scheduled to arrive at Mercury in 2020. The preparation of these missions requires a good knowledge of the rotation of Mercury.     

RECENT PROGRESS IN THE PROJECT OF SPACE SOLAR TELESCOPE

In this paper, we introduce some process of the project of Space Solar Telescope in recent two years. The astronomic requirements have been further identified,the mission and operation requirements have been assessed, and some critical technologies have been performed. According to the time schedule, it is esti mated that the engineering model of the spacecraft would be completed and put into test operation in the end of 2004 and the spacecraft would be launched in about 2007.     

卫星轨道变化规律的综合分析

对于航天工程而言,无论是航天器的发射,卫星轨道设计,地面测控系统的跟踪、定轨和预报．还是卫星在轨运行过程中的轨道控制策略等,均需了解卫星轨道变化的规律。为此,本文对人造卫星(包括中心天体为快自转天体和慢自转天体两种引力源的绕飞轨道器)的轨道变化特征以及轨道寿命进行系统的综合分析。为各种应用提供简明信息。     

基于天文和陆标观测的月球卫星自主导航方法

随着我国月球探测工程的开展,为弥补地面测控的局限性,月球卫星的自主导航技术已成为     

Research on failure criterion of composite based on unified macro- and micro-mechanical model

A new unified macro- and micro-mechanics failure analysis method for composite structures was developed in order to take the effects of composite micro structure into consideration. In this method, the macro stress distribution of composite structure was calculated by commercial finite element analysis software. According to the macro stress distribution, the damage point was searched and the micro-stress distribution was calculated by reformulated finite-volume direct averaging micromechanics (FVDAM), which was a multi-scale finite element method for composite. The micro structure failure modes were estimated with the failure strength of constituents. A unidirectional composite plate with a circular hole in the center under two kinds of loads was analyzed with the traditional macro-mechanical failure analysis method and the unified macro- and micro-mechanics failure analysis method. The results obtained by the two methods are consistent, which show this new method’s accuracy and efficiency.     

纤维棒直径对轴编C/C复合材料拉伸强度的影响

为了研究增强相尺度对轴编C/C复合材料拉伸性能的影响,通过对具有不同直径纤维棒的材料微结构的观测,结合材料的细观和宏观力学性能实验,研究了纤维棒直径引起的材料拉伸性能变化。结果表明:在编织参数不变的情况下,纤维棒直径增加,棒内大尺度裂纹增多,降低了材料的拉伸强度,但模量变化不明显。     

FY-3气象卫星中分辨率光谱成像仪结构仿真分析

用ANSYS软件仿真分析了风云三号（FY-3）气象卫星中分辨率光谱成像仪的结构。根据建立的成像仪有限元模型,进行了静力学、模态和谱分析,给出了X、Y、Z向加速度载荷下消旋机构的应力和变形、1-20阶模态频率,以及各向正弦振动谱作用下各部件的应力和变形。结果表明：有限元法与实验数据基本吻合,可用于成像仪设计的优化。     

Application of CCD drift-scan photoelectric technique on monitoring GEO satellites

Geosynchronous Earth Orbit (GEO) satellites are widely used because of their unique characteristics of high-orbit and remaining permanently in the same area of the sky. Precise monitoring of GEO satellites can provide a key reference for the judgment of satellite operation status, the capture and identification of targets, and the analysis of collision warning. The observation using ground-based optical telescopes plays an important role in the field of monitoring GEO targets. Different from distant celestial bodies, there is a relative movement between the GEO target and the background reference stars, which makes the conventional observation method limited for long focal length telescopes. CCD drift-scan photoelectric technique is applied on monitoring GEO targets. In the case of parking the telescope, the good round images of the background reference stars and the GEO target at the same sky region can be obtained through the alternating observation of CCD drift-scan mode and CCD stare mode, so as to improve the precision of celestial positioning for the GEO target. Observation experiments of GEO targets were carried out with 1.56-meter telescope of Shanghai Astronomical Observatory. The results show that the application of CCD drift-scan photoelectric technique makes the precision of observing the GEO target reach the level of 0.2″, which gives full play to the advantage of the long focal length of the telescope. The effect of orbit improvement based on multi-pass of observations is obvious and the prediction precision of extrapolating to 72-h is in the order of several arc seconds in azimuth and elevation.     

面向小推力变轨的天文组合自主导航方法

针对小行星探测任务对导航系统自主性强、实时性高的需求,研究了一种面向小推力变轨的天文组合自主导航方法。根据工程实践分析并建立了电推进变轨过程中的动力学模型,给出了天文测角测速组合的小行星探测自主导航方案。为克服小行星探测器推力的不确定性,提出了采用自适应交互式多模型无迹卡尔曼滤波(AIMM-UKF)算法,以较少的模型个数实现对导航系统状态的覆盖,克服了模型集合先验信息不准确对导航精度的影响,提高了组合导航系统的鲁棒性和抗干扰能力。最后,通过数学仿真对组合导航算法的性能进行了验证,结果表明本文提出的组合导航方法估计精度更高、计算消耗更小,可满足小行星探测工程任务对导航系统自主性、实时性和高精度的需求。     

A new method of single celestial-body sun positioning based on theory of mechanisms

Considering defects of current single celestial-body positioning methods such as discon-tinuity and long period, a new sun positioning algorithm is herein put forward. Instead of tradi-tional astronomical spherical trigonometry and celestial coordinate system, the proposed new positioning algorithm is built by theory of mechanisms. Based on previously derived solar vector equations (from a C1R2P2 series mechanism), a further global positioning method is developed by inverse kinematics. The longitude and latitude coordinates expressed by Greenwich mean time (GMT) and solar vector in local coordinate system are formulated. Meanwhile, elimination method of multiple solutions, errors of longitude and latitude calculation are given. In addition, this algo-rithm has been integrated successfully into a mobile phone application to visualize sun positioning process. Results of theoretical verification and smart phone’s test demonstrate the validity of pre-sented coordinate’s expressions. Precision is shown as equivalent to current works and is acceptable to civil aviation requirement. This new method solves long-period problem in sun sight running fix-ing and improves applicability of sun positioning. Its methodology can inspire development of new sun positioning device. It would be more applicable to be combined with inertial navigation systems for overcoming discontinuity of celestial navigation systems and accumulative errors of inertial nav-igation systems.