连续地月转移系统动力学研究与能量分析

为了研究新型连续地月转移系统的动力学及能量需求,采用Lagrange方法,在系绳为刚性杆假设的前提下,同时忽略第三体引力、地球扁率和系绳轴向变形等扰动因素的影响,建立了驱动型动量交换绳系卫星(MMET)系统的三维刚性动力学模型。对所建立的动力学模型进行了数值仿真及对比分析,仿真结果验证了所建模型的正确性。研究表明,外力矩对系统轨道运动参数影响甚小,对姿态运动参数影响明显。采用MMET方式进行载荷转移,推导出了实现载荷地月轨道转移所需的入口速度条件以及时间周期条件,并求解出了载荷在2次任务之间的时间间隔。给定初始条件下,当MMET系统以0.231 6 rad/s的旋转角速度绕其质心旋转1 448.5圈,其绕地心刚好运行5圈时,载荷可顺利进入地月转移轨道。最后,对连续地月转移系统实现载荷的地月转移进行了能量对比分析,结果表明,相同条件下,MMET载荷转移方式相比于传统脉冲变轨方式在载荷转移过程中消耗更少的能量。     

I: PRECISE ORBIT DETERMINATION AND GRAVITY FIELD MODELLING: Strategies for Precise Orbit Determination of Low Earth Orbiters Using the GPS

Considerable experience accumulated during the past decade in strategies for processing GPS data from ground-based geodetic receivers. First experience on the use of GPS observations from spaceborne receivers for orbit determination of satellites on low altitude orbits was gained with the launch of TOPEX/POSEIDON ten years ago. The launch of the CHAMP satellite in July 2000 stimulated a number of activities worldwide on improving the strategies and algorithms for orbit determination for Low Earth Orbiters (LEOs) using the GPS. Similar strategies as for ground-based receivers are applied to data from spaceborne GPS receivers to determine high precision orbits. Zero- and double-differencing techniques are applied to obtain kinematic and/or reduced-dynamic orbits with an accuracy which is today at the decimeter level. Further developments in modeling and processing strategies will continuously improve the quality of GPS-derived LEO orbits in the near future. A significant improvement can be expected from fixing double-difference phase ambiguities to integer numbers. Particular studies focus on the impact of a combined processing of LEO and GPS orbits on the quality of orbits and the reference frame realization. This revised version was published online in August 2006 with corrections to the Cover Date.     

21世纪AMSS／GNSS空间段发展方向兼论卫星资源国际共享问题

航空移动卫星系统（ＡＭＳＳ）空间段采用单一的ＧＥＯ轨道卫星，未来将有ＭＥＯ和ＬＥＯ轨道卫星加入运行，仍然不排斥ＧＥＯ轨道卫星的使用。全球导航卫星系统（ＧＮＳＳ）空间段采用ＭＥＯ轨道卫星，未来将仍然以ＭＥＯ为主，可能有ＨＥＯ轨道卫星加入运行。２１世纪的空间段将为不同轨道卫星的多星座组合，采用一星多用、星座共用，形成多功能卫星和多功能星座。和平时期卫星资源的国际民间共建共营共享将更为普遍，要有全球观点，国内各行各业要有全局观点，对监测和增强系统统一筹建共用系统，防止分散投资、重复建设     

Line-of-sight-pointing for satellites in high altitude inclined elliptic orbits

With a growing demand for space communications and resulting overcrowding of geostationary orbit (GEO), the importance of high altitude inclined elliptic orbits is gaining impetus. However, the satellites in these orbits suffer from a severe problem of apparent periodic angular drift around their line-of-sight. This paper addresses this problem and proposes a cost effective method based on tether to continually tilt the satellites in order to compensate for longitudinal and lateral drifts relative to the ground station. The proposed system comprises two satellites connected by a flexible tether at a point on each satellite with offsets. A control strategy is developed for tether offset variations that ensures judiciously controlled changes in the satellite orientations. The numerical simulation of the governing nonlinear equations of motion establishes the feasibility of the concept. A high degree of line-of-sight pointing of dual satellites as well as the simplicity of the proposed control mechanism makes the concept particularly attractive for future space applications.     

Satellite Skin-Force Modelling for Atmospheric Drag Calculations

Satellites in low Earth orbits are influenced by the Earth’s atmosphere. The interactions between the molecules and the spacecraft cause the highest non-gravitational force, which in magnitude is comparable to planetary disturbances. Therefore the modelling of atmospheric drag effects is important for many missions with a scientific background like STEP (Satellite Test of Equivalence Principle). With the STEP mission variations between gravitational and inertial mass shall be measured with an accuracy of 10^?18. The results are of great interest for cosmological and gravitational theories. To achieve the aimed accuracy, a precise model of external disturbances is necessary. In this article the method of Ray-Tracing is used to quantify the atmospheric drag forces and torques for spacecrafts of arbitrary shape.     

Determination des orbites des satellites artificiels

Summary The problem of the determination of the orbit of a celestial body is an old astronomical problem, of which solutions can be found in many classical books on elementary celestial mechanics. However, the introduction of new (radioelectric) means of observations for the artificial satellites have brought up new solutions of this old problem.The author reminds the definitions of the six elliptic elements of an orbit. The problem of their determination is usually divided into two separate steps: a preliminary orbit determination and the improvement of the preliminary elements. Two principal types of preliminary orbit determination exist: the Gaussian type, purely geometrical in which the positions of the body at two different times are determined, and the Laplacian type, of a more dynamical character, in which both position and velocity vectors are found for a given time. The improvement of the preliminary elements is usually obtained by a numerical solution of equations of variations of the elements, minimizing the sum of the squares of the angular distances between the computed and the observed points. The elements on which these variations are applied can be quite various. The coefficients of the equations are usually obtained numerically, although their analytical expressions can also be derived.Most of the modification proposed to the classical methods of orbit determination are more technical improvements in connection with the computation on electronic machines. The most interesting modifications are inspired by the fact that time measurements are less precise than the position (Batrakov, Iszak), the effects of this difference in errors are discussed in this paper. In some cases, using Laplace's method, no preliminary orbit is computed, and all the observations can be used at once (Barlier, Kovalevsky).The determination of orbits from radar measurements is discussed. The proposed methods are quite different in principle from the classical ones. They are actually improvements of a circular orbit whose determination is made by a method of undetermined coefficients (Baker). Some of the elements determined by these methods are quite unstable, and it is always wiser to use other informations together with radar measurements.The determination of orbits from Doppler data alone has been worked out by many investigators. It is the inverse problem of the main problem of all navigational systems. The method proposed by Patton is summarized. The principles of others are quite analogous. The results are improved when more than one receiver are used. The different types of corrections: refraction, perturbations, etc., should be introduced in later stages of the determination, and the whole frequency curve is to be used if a good determination of all elements is desired.Finally, the author quotes a method (Baker) using both Doppler and radar data, and the solution of a new problem: the determination of the orbit of a satellite of another planet from Doppler data alone (Deutsch).     

Selecting and scheduling observations of agile satellites

This article concerns the problem of managing the new generation of Agile Earth Observing Satellites (AEOS). This kind of satellites is presently studied by the French Centre National d'Études Spatiales (PLEIADES project). The mission of an Earth Observing Satellite is to acquire images of specified areas on the Earth surface, in response to observation requests from customers. Whereas non-agile satellites such as SPOT5 have only one degree of freedom for acquiring images, the new generation satellites have three, giving opportunities for a more efficient use of the satellite imaging capabilities. Counterwise to this advantage, the selection and scheduling of observations becomes significantly more difficult, due to the larger search space for potential solutions. Hence, selecting and scheduling observations of agile satellites is a highly combinatorial problem. This article sets out the overall problem and analyses its difficulties. Then it presents different methods which have been investigated in order to solve a simplified version of the complete problem: a greedy algorithm, a dynamic programming algorithm, a constraint programming approach and a local search method.     

Rosette Constellations of Earth Satellites

Satellite constellations having rosette (flowerlike) orbital patterns are described which exhibit better worldwide coverage properties than constellations previously reported in U.S. literature. The best rosettes with 5-15 satellites are identified and evaluated relative to prior results. In most cases, the best results are obtained by placing one satellite in each of N separate planes and by using inclined rather than polar orbits. Coverage properties of these constellations are analyzed in terms of the largest possible great circle range between an observer anywhere on the Earth's surface and the nearest subsatellite point. When evaluated in this manner, coverage properties are invariant with deployment altitude. As deployment altitude is reduced, however, higher order constellations must be used to maintain a fixed minimum viewing angle. Coverage properties are also invariant with deployment orientation relative to Earth coordinates, although specific orientations can cause the satellite patterns to appear quasi-stationary. Thus these constellations offer a promising alternative to the use of geostationary satellites. Rosette constellations can also be used to guarantee multiple satellite visibility on a continuous worldwide basis. It is shown that 5, 7, 9, and 11 satellites are the minimum numbers required for single, double, triple, and quadruple visibility, respectively. Examples of rosette constellations which achieve these bounds are given.     

MARC-a system for simulation and visualization of space missionscenarios

MARC (modeling, animation, rendering, and compositing), a system using advanced computer graphics and animation techniques for spacecraft mission simulation, is described. The MARC system provides capabilities for generating complex models of both man-made and natural phenomena. The system models orbital dynamics of terrestrial satellites, supports solid models for the Earth, Sun, and Moon, and simulates the dynamics of terrestrial satellites for arbitrary elliptical orbits. A stellar background including magnitudes and spectral types is generated. The elements of the MARC system, including object modeling tools, orbital animation techniques, the rendering system used to compute individual frames, and the compositing techniques used, are discussed. The software architecture of the MARC system and the hardware used to support the system are described     

Preliminary Analysis of a Proposed High-Stability Frequency Standard Distribution System

A system for distributing a frequency reference, which involves the use of geostationary satellites and two-way microwave transmissions, seems capable of stabilities exceeding those of primary atomic standards. The principal sources of error are instabilities in oscillators in the system, imperfect geostationary orbits, additive noise, and radio propagation effects. Even extreme assumptions of propagation phase instability lead to very small errors. Thus the limitations on stability seem to be imposed by the hardware.     

Monopulse Resolution of Interferometric Ambiguities

Ambiguities in interferometers with high angular accuracy must be resolved to achieve a practical system design. A new technique for ambiguity resolution is described and is based on monopulse circuitry used with the interferometric elements. The overall angular accuracy of the system is achieved by the interferometer; the angular accuracy of the monopulse subsystem is used to resolve interferometric ambiguities. An expression for the probability of correct ambiguity resolution is derived as a function of element size and monopulse accuracy which indicates that high probability of ambiguity resolution results when the size of the interferometric elements are a fraction of the interferometric baseline. Finally, a comparison between conventional monopulse and interferometric system designs is made for the three principal parameters, signal sensitivity, angular accuracy, and field of view, that dictate the appropriate choice for a particular application. Interferometric systems are more appropriate than monopulse systems for those applications in which angular accuracy and field of view are more important than signal sensitivity.     

中继卫星天线指向控制策略研究

首先根据中继卫星系统中中继卫星跟踪用户星的要求,定义了中继卫星天线坐标系,推导出了中继卫星天线对用户星的跟踪规律,通过该跟踪规律可以推出中继卫星跟踪用户星时天线方位和俯仰轴转角,为了保证中继卫星与用户星之间的通信,中继卫星单址天线需要精确的指向用户星;然后详细描述了天线指向控制概念,并且设计了星上自主控制方案,星上自主控制方案由捕获和自动跟踪模式组成,一方面设计了天线捕获过程,另一方面对自动跟踪模式的天线步进逻辑进行了合理选择;最后根据推导的跟踪规律,以不同轨道的用户星作为跟踪目标,对所设计的天线指向控制系统进行了数学仿真,并且通过对仿真结果的分析验证了中继卫星单址天线指向性能。     

The rotational speed of the upper atmosphere

This paper describes the method for determining the rotational speed of the Earth's upper atmosphere from the changes in the orbital inclinations of satellites, and briefly reviews the observational results so far obtained at heights above 180 km, both by this method and by measuring the movements of vapour trails. The results from satellite orbits indicate that the upper atmosphere at heights of 200–300 km is on average rotating 1.3 times faster than the Earth, corresponding to a mean west-to-east wind of about 100 m/s in mid latitudes. The physical processes which may control upper-atmosphere movements are outlined, and possible mechanisms for the observed motions are briefly discussed. It should be emphasized that the subject is full of uncertainties, and this paper is intended to draw attention to the difficulties, rather than to provide a coherent picture of the actual conditions.     

Design of Satellite Constellations for Optimal Continuous Coverage

A satellite-borne sensor can view a region at or above the Earth's surface. The size of this region depends on the satellite's altitude, the maximum range and scan angle of the sensor, the minimum above-the-horizon viewing angle required, the extent in altitude of the region to be viewed, and the maximum altitude of sensor obscuration by the atmosphere. Except for geosynchronous satellites this region moves relative to the Earth, so that constellations of satellites are generally necessary for continuous coverage. Satellite constellations which minimize the number of satellites required for continuous coverage are derived as a function of the angle subtended at the Earth's center by the coverage of a single satellite. This is done for single and triple continuous coverage of the entire Earth and of the polar regions extending to arbitrary latitude. Simple, cogent approximations for the configurations and numbers of satellites are found. Expressions which relate sensor capabilities and surveillance requirements to are presented. Examples are given to illustrate the use and accuracy of the results.     

单点弹道精度与轨道半长轴远地点高度计算精度的映射关系

在仅使用单点位置、速度信息计算轨道的奈件下,针对轨道半长轴、远地点高度的精度问题,在轨道面内,应用活力公式和二体运动学理论推导得出了轨道计算精度与弹道测量精度间映射关系的解析表达式,并采用数值分析方法给出了不同的位置、速度误差与半长轴、远地点高度最大误差之间的数值关系.仿真结果表明,对于位置误差和速度误差大小分别为100 m和1 m/s的算例,半长轴最大误差和远地点高度最大误差分别约为2 km和4 km.基于此方法,可以将弹道误差传递至轨道参数误差,进一步分析故障误判和漏判概率;也可根据轨道参数精度要求反算弹道测量精度要求,以作为地面测量系统建设的技术依据.     

旋转调制式惯性平台的圆锥运动误差

转调制式空间稳定平台采用陀螺壳体翻滚技术,陀螺壳体翻滚在平台伺服跟踪作用下将形成圆锥运动。圆锥运动误差会引起陀螺漂移,对高精度、长航时惯性导航系统的精度将造成严重影响。首先,介绍了高精度、长航时旋转调制式惯性平台的基本工作原理,推导了平台上的陀螺沿旋转主轴相对地球的角速度。其次,阐述了陀螺壳体翻滚的圆锥运动,推导了壳体翻滚装置和框架伺服系统的跟踪误差及牵连运动角速度引起的圆锥运动附加漂移误差公式。再次,根据数值举例给出了计算机仿真曲线,指出该误差对高精度系统的危害。最后,得出结论：为了实现圆锥运动误差极小化,确保系统长时间运行精度和可靠性,必须实时扣除牵连运动角速度引起的圆锥运动误差分量,并优化设计壳体翻滚装置与平台伺服系统。     

Aiming at a 1-cm Orbit for Low Earth Orbiters: Reduced-Dynamic and Kinematic Precise Orbit Determination

The computation of high-accuracy orbits is a prerequisite for the success of Low Earth Orbiter (LEO) missions such as CHAMP, GRACE and GOCE. The mission objectives of these satellites cannot be reached without computing orbits with an accuracy at the few cm level. Such a level of accuracy might be achieved with the techniques of reduced-dynamic and kinematic precise orbit determination (POD) assuming continuous Satellite-to-Satellite Tracking (SST) by the Global Positioning System (GPS). Both techniques have reached a high level of maturity and have been successfully applied to missions in the past, for example to TOPEX/POSEIDON (T/P), leading to (sub-)decimeter orbit accuracy. New LEO gravity missions are (to be) equipped with advanced GPS receivers promising to provide very high quality SST observations thereby opening the possibility for computing cm-level accuracy orbits. The computation of orbits at this accuracy level does not only require high-quality GPS receivers, but also advanced and demanding observation preprocessing and correction algorithms. Moreover, sophisticated parameter estimation schemes need to be adapted and extended to allow the computation of such orbits. Finally, reliable methods need to be employed for assessing the orbit quality and providing feedback to the different processing steps in the orbit computation process. This revised version was published online in August 2006 with corrections to the Cover Date.     

中继卫星复合控制系统设计

根据中继卫星系统多体控制的特点，合理地选择了中继卫星复合控制系统方案；然后根据所选择的方案，分别设计了中继卫星星体姿态稳定控制系统和单址天线指向控制系统，详细描述了天线指向控制概念，并且设计了星上自主控制方案；最后以不同的用户星作为跟踪目标，对所设计的复合控制系统进行了数学仿真。通过对仿真结果的分析，验证了该系统的有效性。     

低轨卫星多普勒频移特性的快速计算

地面站利用低轨卫星进行通信时,地面接收站接收信号存在明显的多普勒频移现象。为描述多普勒频移特性,首先分析卫星轨道偏心率对多普勒特性曲线的影响,分析表明：轨道偏心率越大,地面站接收信号多普勒变化率越大。其次,推导了卫星多普勒频移的计算表达式,并讨论了低轨卫星多普勒频移特性曲线的快速计算。仿真计算结果表明,该算法可以很好地描述任意低轨道卫星多普勒频移特性,并明显缩短了精确算法的计算时间,对于10 000km轨道高度卫星,算法置信度可达99%以上。     

Application of the Abel equation to describe the precession motion of a gyrostabilized platform

The angular velocity of the gyrostabilized platform (GSP) precession motion is described using the second-kind Abel equation. It is shown that this method offers the advantage over the existing approaches that consists in the use of a minimal number of assumptions in constructing the GSP drift model. The results of the numerical simulation are presented.