关于HEO空间飞行体的轨道寿命问题

低轨地球卫星的轨道寿命主要取决于大气的耗散作用,其轨道在不断变小(即高度降低)变圆的状态下进入地球稠密大气层中陨落.但HEO(Highly Eccentric Orbit)类型的空间飞行体的运行轨道是一个近地点高度很低,远地点高度却很高的大偏心率椭圆轨道,其轨道寿命主要由第三体(日、月)引力摄动所决定,而且还与其轨道的初始状态有密切关系,特别是慢变量Ω(轨道升交点经度)和ω(轨道近地点幅角),决定了偏心率e的长周期变化状态,从而制约了HEO类型空间飞行体的轨道寿命.本文将根据地球卫星轨道变化规律进行理论分析,阐明这一力学机制,并给出相应的数值验证.      

基于解体事件的空间碎片轨道演化算法研究

针对航天器解体事件所生成的空间碎片的演化过程,进行了数学分析,确定了新生成的空间碎片的速度增量,在该增量作用下碎片轨道会发生变更,本文根据该增量得出了空间碎片在轨道变更后的轨道根数,分析了在大气阻力摄动作用下,空间碎片的数目和轨道分布的演化情况,给出了相关结果,结果表明此算法可行。     

大气阻力参数修正对低轨空间目标轨道预报精度的改进

对于低轨空间目标, 大气阻力是影响轨道预报精度的主要摄动力. 本文提出了一种 基于空间环境数据和神经网络模型的空间目标大气阻力参数修正方法, 基于目 标的历史两行元根数, 通过模拟得到外推一天轨道预报中预报结果与观测数据 符合最好的阻力调制系数, 分析表明其与太阳F_10.7指数和地磁Ap指数具有很好的相关性. 根据已有数据, 构建神经网络模型, 实现对阻力调制系数 的补偿计算, 从而改进低轨目标外推一天的轨道预报. 结果表明, 神经网络模 型相比两行元根数能够更及时地对空间环境变化进行响应. 将该方案应用于天 宫一号和国际空间站的外推一天轨道预报, 验证了方案的正确性和普适性, 对 地磁扰动引起的较大预报误差改进效果更好, 误差能够降低50%~60%; 平均而言, 预报精度可以提高约30%, 改进成功率达到80%左右.      

双通道辐射量计算太阳极紫外辐射E10.7指数方法初探

从太阳极紫外辐射研究的重要性出发, 介绍了太阳极紫外辐射E_10.7指 数及其作用, 详细阐述了利用两个能道的太阳辐射观测值计算极紫外辐射E_10.7指数的计算方法. 利用该方法对实测太阳辐射数据进行处理, 计算获得了2000-2005年的每日E_10.7指数, 并将计算结果 与Solar2000模式的输出结果进行对比分析, 验证了该计算方法的可行性, 对比结果表明, 最大相对误差在20%以内, 平均相对误差均在10%以内.      

一种基于TLE数据的轨道异常分析方法

空间在轨物体的轨道异常是航天工程及预警领域普遍关注的问题,及时发现轨道异常意义重大,通过分析空间物体的轨道异常,可以及时发现和识别规避事件或碰撞事件,还可以了解监测网的能力.本文提出一种基于TLE数据的简单的轨道异常分析方法——长半轴变化法.该方法快速有效,应用到低轨在用卫星和美俄解体碎片的异常分析中,异常物体正确识别率可达到100%;对美俄解体碎片进行轨道异常分析后得出,美国空间监视网可以稳定探测90%以上的解体碎片.      

解体速度增量计算方法研究

解体速度增量是解体事件强度的重要指征, 它决定了解体产生碎片的轨道分布. 通过分析解体速度增量可以推断解体强度, 确定解体形式. 解体速度增量有两种计算方法, 即轨道位置演化法和轨道面相交法. 轨道位置演化法是根据解体前后轨道速度的变化直接得到解体速度增量; 而轨道面相交法是利用母体以及解体碎片的球面三角几何关系, 根据解体碎片的倾角和升交点赤经变化, 以及母体轨道的倾角和近地点辐角, 计算解体时刻母体轨道的真近点角, 从而得到解体的时间和速度增量. 相比来说, 轨道位置演化法适用于数据精度高, 解体高度高情况下的解体事件分析, 而轨道面相交法适用于解体高度低, 碎片数据公布时间较为滞后的解体事件分析. 根据解体速度增量的计算方法及其原理, 对两种方法的适用性进行了比较和讨论, 并选取已经发生的三次解体事件, 利用美国公布的TLE数据, 针对具体情况选择计算方法, 给出了三次解体事件发生的时间和解体碎片在空间三个方向上的速度增量.      

基于多项式近似的空间碎片群体轨道预报算法

快速准确地分析空间碎片群轨道演化行为对于其他在轨航天器碰撞规避至关重要。在各摄动力的作用下,空间碎片群演化运动呈现出复杂的非线性特征。空间碎片群体个体数量巨大,如果通过对空间碎片群中每个空间碎片进行轨道积分来分析群体预报的方法会导致计算量过大。针对该问题,提出一种基于多项式近似的轨道快速预报分析方法。该方法将空间碎片群分为少量的标称碎片和其他大量关联碎片。针对标称碎片的轨道预报采用数值积分求解保证预报精度;而针对其他大量的关联碎片轨道预报问题,采用多项式泰勒展开半解析方法求解,从而在保证预报精度的前提下有效减少空间碎片群轨道预报的计算量。为了验证方法的有效性,对不同空间碎片群进行了轨道预报仿真。仿真结果表明,当轨道预报精度设定在1m范围内时,多项式近似算法的计算量较蒙特卡洛方法计算效率提高了2.2~17.2倍,验证了所提出方法的有效性。     

横向连续推力小偏心率人工冻结轨道设计

非临界倾角自然冻结轨道要求近地点幅角为90°, 偏心率在1× 10-3量级, 并且偏心率与轨道倾角和半长轴有特定的对应关系, 苛刻的要求极大地限制了轨道根数选择的多样性. 研究表明, 施加常幅值、方向半轨道周期切换的横向连续小推力可以形成任意轨道根数的小偏心率人工冻结轨道, 放宽自然冻结轨道对轨道根数的严苛限制. 维持小偏心率人工冻结轨道的横向连续推力a_T与半长轴的平方根成正比, 与偏心率大小成反比; 在临界倾角i_c附近, 推力a_T与倾角偏置量Δi近似呈正比, 且长期维持的燃料消耗较小. 此外, 在进行仿真计算时还需考虑拟平均轨道根数与瞬时轨道根数的转换.      

基于金星共振借力的太阳抵近探测任务轨道设计

对于太阳抵近探测任务,从地球直接发射探测器至太阳附近需要消耗巨大能量,通过多次金星借力飞行,可有效降低地球发射能量C₃及中途变轨的燃料消耗.本文研究基于金星共振借力的太阳抵近探测任务轨道优化设计,建立了连续共振借力和混合共振借力的转移轨道优化设计模型,并针对2025—2028年的发射窗口开展太阳抵近探测任务轨道优化设计.仿真结果表明,相比连续共振借力,混合共振借力可以有效缩短太阳抵近探测任务的轨道转移时间,对于地球发射能量C₃和中途变轨燃料消耗的影响未见明显的规律性,能量降低与序列中的共振比相关.      

太阳同步冻结轨道星座保持与捕获

太阳同步冻结轨道卫星在经过同一星下点时光照特性和轨道高度相同，便于载荷观测及定标.由多颗太阳同步冻结轨道卫星组成的星座，需要实现星座成员轨道倾角、轨道高度、偏心率矢量和相对轨道幅角的同时保持.提出了基于切向单脉冲的最低燃耗轨道面内保持策略，证明了该策略的稳定性和燃料最优性， 给出了太阳同步轨道地方时保持简单算法.仿真证明，基于本策略的星座成员能跟踪并捕获目标轨道.面内保持策略还可用于低轨卫星编队低燃耗控制.     

The classical Laplace plane as a stable disposal orbit for geostationary satellites

The classical Laplace plane is a frozen orbit, or equilibrium solution for the averaged dynamics arising from Earth oblateness and lunisolar gravitational perturbations. The pole of the orbital plane of uncontrolled GEO satellites regress around the pole of the Laplace plane at nearly constant inclination and rate. In accordance with Friesen et al. (1993), we show how this stable plane can be used as a robust long-term disposal orbit. The current graveyard regions for end-of-life retirement of GEO payloads, which is several hundred kilometers above GEO depending on the spacecraft characteristics, cannot contain the newly discovered high area-to-mass ratio debris population. Such objects are highly susceptible to the effects of solar radiation pressure exhibiting dramatic variations in eccentricity and inclination over short periods of time. The Laplace plane graveyard, on the contrary, would trap this debris and would not allow these objects to rain down through GEO. Since placing a satellite in this inclined orbit can be expensive, we discuss some alternative disposal schemes that have acceptable cost-to-benefit ratios.     

Dynamical evolution of high area-to-mass ratio objects in Molniya orbits

For special demands, some notable orbit types have been developed by human, including the Molniya orbits, which have a relatively high eccentricity up to about 0.7, and a period of 12 h. Considering that space debris with high area-to-mass ratio (A/M) has been discovered, such objects may also exist in Molniya orbits due to spacecraft and upper stages fragmentation events. However, there are not sufficient studies of the complex dynamical phenomena of such orbits. These studies can enrich the knowledge about the long-term evolution of these orbits, be helpful to propose uncatalogued objects observation and identification, and also set the protected region as well as active debris removal. In this paper, the characteristics of 2:1 resonance of Molniya satellite orbits are studied. A large set of numerical simulations, including all the relevant perturbations, is carried out to further investigate the main characteristics, and special attention is payed to the dynamical evolution of objects with high A/M, particularly affected by the direct solar radiation pressure. The long-term dynamical evolution of orbital elements, as well as the dependency of lifetime on the A/M value, is discussed.     

Semi-analytical theory of mean orbital motion for geosynchronous space debris under gravitational influence

This paper provides a hamiltonian formulation of the equations of motion of an artificial satellite or space debris orbiting the geostationary ring. This theory of order 1 has been formulated using canonical and non-singular elements for eccentricity and inclination. The analysis is based on an expansion in powers of the eccentricity and of the inclination. The theory accounts for the influence of the Earth gravity field expanded in spherical harmonics, paying a particular attention to the resonance occurring for geosynchronous objects. The luni-solar perturbations are also taken into account. We present the resonant motion and its main characteristics: equilibria, stability, fundamental frequencies and width of the resonant area by comparison with a basic analytical model. Finally, we show some results concerning the long term dynamics of a typical space debris under the influence of the gravitational field of the Earth and the luni-solar interactions.     

A deformation model of flexible,HAMR objects for accurate propagation under perturbations and the self-shadowing effects

A new type of space debris in near geosynchronous orbit (GEO) was recently discovered and later identified as exhibiting unique characteristics associated with high area-to-mass ratio (HAMR) objects, such as high rotation rates and high reflection properties. Observations have shown that this debris type is very sensitive to environmental disturbances, particularly solar radiation pressure, due to the fact that its motion depends on the actual effective area, orientation of that effective area, reflection properties and the area-to-mass ratio of the object is not stable over time. Previous investigations have modelled this type of debris as rigid bodies (constant area-to-mass ratios) or discrete deformed body; however, these simplifications will lead to inaccurate long term orbital predictions. This paper proposes a simple yet reliable model of a thin, deformable membrane based on multibody dynamics. The membrane is modelled as a series of flat plates, connected through joints, representing the flexibility of the membrane itself. The mass of the membrane, albeit low, is taken into account through lump masses at the joints. The attitude and orbital motion of this flexible membrane model is then propagated near GEO to predict its orbital evolution under the perturbations of solar radiation pressure, Earth’s gravity field (J₂), third body gravitational fields (the Sun and Moon) and self-shadowing. These results are then compared to those obtained for two rigid body models (cannonball and flat rigid plate). In addition, Monte Carlo simulations of the flexible model by varying initial attitude and deformation angle (different shape) are investigated and compared with the two rigid models (cannonball and flat rigid plate) over a period of 100?days. The numerical results demonstrate that cannonball and rigid flat plate are not appropriate to capture the true dynamical evolution of these objects, at the cost of increased computational time.     

Cosmos 2421卫星解体事件分析

2008年上半年俄罗斯的Cosmos 2421卫星接连发生了三次不同程度的解体, 并产生了数百颗碎片. 本文利用美国公布的Cosmos 2421卫星及其碎片的两行根数系列, 对三次解体事件发生的时间, 解体碎片的轨道分布、速度分布和面积质量比以及寿命等进行了分析, 并对解体碎片对航天器的影响进行了评估. 分析结果表明, Cosmos2421卫星的三次解体事件分别发生在2008年3月14日、4月28日、6月9日; 解体碎片分布在200~1400 km 的高度范围内; Cosmos 2421卫星解体导致的碎片在空间三个方向上的速度增量均值分别为-8.4m/s, 8.6m/s, -8.3m/s; 67\%的解体碎片的寿命都在1年以内, 解体事件造成500 km以下的空间碎片空间密度增加, 对载人航天器产生了影响. 通过对Cosmos 2421卫星解体事件的分析可以看出, 利用解体碎片的轨道信息可以反演解体事件特性, 根据解体碎片的寿命和空间密度分布的计算结果可以评估解体事件对未来发射活动和在轨卫星的影响.      

Analytical and semi-analytical investigations of geosynchronous space debris with high area-to-mass ratios

This paper provides a Hamiltonian formulation of the averaged equations of motion with respect to short periods (1 day) of a space debris subjected to direct solar radiation pressure and orbiting near the geostationary ring. This theory is based on a semi-analytical theory of order 1 regarding the averaging process, formulated using canonical and non-singular elements for eccentricity and inclination. The analysis is based on an expansion in powers of the eccentricity and of the inclination, truncated at an arbitrary high order.     

Properties of the high area-to-mass ratio space debris population at high altitudes

In the framework of its space debris research activities ESA established an optical survey program to study the space debris environment at high altitudes, in particular in the geostationary ring and in the geostationary transfer orbit region. The Astronomical Institute of the University of Bern (AIUB) performs these surveys on behalf of ESA using ESA’s 1-m telescope in Tenerife. Regular observations were started in 1999 and are continued during about 120–140 nights per year. Results from these surveys revealed a substantial amount of space debris at high altitudes in the size range from 0.1 to 1 m. Several space debris populations with different dynamical properties were identified in the geostationary ring. During the searches for debris in the geostationary transfer orbit region a new population of objects in unexpected orbits, where no potential progenitors exist, was found. The orbital periods of these objects are clustered around one revolution per day; the eccentricities, however, are scattered between 0 and 0.6. By following-up some of these objects using the ESA telescope and AIUB’s 1-m telescope in Zimmerwald, Switzerland, it was possible to study the properties of this new population. One spectacular finding from monitoring the orbits over time spans of days to months is the fact that these objects must have extreme area-to-mass ratios, which are by several orders of magnitudes higher than for ‘normal-type’ debris. This in turn supports the hypothesis that the new population actually is debris generated in or near the geostationary ring and which is in orbits with periodically varying eccentricity and inclination due to perturbations by solar radiation pressure. In order to further study the nature of these debris, multi-color and temporal photometry (light curves) were acquired with the Zimmerwald telescope. The light curves show strong variations over short time intervals, including signals typical for specular reflections. Some objects exhibit distinct periodic variations with periods ranging from 10 to several 100 s. All this is indicative for objects with complicated shapes and some highly reflective surfaces.     

基于SAMPEX卫星观测的南大西洋异常区高能质子动态分布特征

利用SAMPEX卫星1992年7月至2004年6月19～27MeV高能质子数据对南大西洋异常区的分布特征进行研究, 发现南大西洋异常区高能质子分布随高度及F_10.7的变化十分显著. 在540±25km高度上, 地磁较为平静时期南大西洋异常区高能质子微分通量随着F_10.7的增大而减小, 同时在F_10.7≥115sfu时减小趋势较为平缓. 对中等及以上磁暴进行统计分析发现, 磁暴期间南大西洋异常区高能质子微分通量和SYM-H指数的绝对值存在明显的反相关关系, 且地磁暴对南大西洋异常区高能质子微分通量存在明显的持续影响效应. 磁暴发生期间高能质子微分通量明显减少. 磁暴恢复相及其之后高能质子微分通量呈现较为显著的恢复过程.