近地小行星(10302) 1989 ML和(4660) Nereus的轨道特征及演化分析

近地小行星(10302) 1989 ML和(4660) Nereus作为下一代深空探测的候选目标一直备受关注. 在考虑太阳系主要天体的动力学背景下, 通过计算最大Lyapunov指数(MLE)及MEGNO (Mean Exponential Growth factor of Nearby Orbits)指数讨论它们的稳定性. 同时, 对每个小行星, 在其观测误差范围内按多元正态分布各选取1000个克隆粒子, 通过统计分析显示这两个小行星在10万年内可能的运动范围, 给出半长径-偏心率空间中的出现次数分布图, 并统计小行星与地球或其他大行星之间的密近交汇及碰撞的概率. 此外还对这两个小行星的标称轨道进行长期共振、Kozai共振及平运动共振的动力学分析. 综上得出结论, 1989 ML处在平运动共振主导的区域, 发生密近交汇的概率较小, 从而其轨道相对较稳定; 而Nereus处在地球的密近交汇区域, 轨道极不稳定.     

地月DRO星载光学测量近地小行星轨道确定

针对地基光学监测系统对近地小行星在近太阳方向的监测存在盲区的问题,提出了远距离逆行轨道(Distant Retrograde Orbit,DRO)天基光学平台对近地小行星进行跟踪定轨的方法.通过可视性分析,筛选仿真观测数据,利用美国宇航局喷气推进实验室(Jet Propulsion Laboratory,JPL)公布的小行星初始轨道信息对不同轨道类型的目标天体进行轨道确定,将计算结果与参考轨道对比分析.仿真结果表明:在测量精度2角秒,定轨弧长3年的情况下,DRO平台对仿真算例中所选择的近地小行星的定轨精度可以达到几十公里量级,其中Atira型轨道精度可达10公里以内.由此可见,DRO天基平台对近地小行星具有较好的监测能力,定轨精度能实现对目标小行星的精确跟踪,并对其进行轨道预报.     

天体轨道长期数值积分的误差估计方法

数值积分方法是进行天体力学研究的重要工具, 尤其对于行星历表的研究工作而言. 由于在使用数值方法计算天体轨道时, 最终误差通常是难以预知的, 所以在面对精度要求较高或者积分时间较长的工作时具体积分方案的设计---尤其是当使用定步长方法时的步长选择---需要十分谨慎, 因为这将意味着是否能在时间成本可以被接受的范围内使解的精度达到要求. 因此, 在使用数值方法解决实际问题时如何快速寻找效率与精度之间的最佳平衡点是每一个数值积分方法的设计者与使用者都会面临的难题. 为解决这一问题, 在定步长条件下对数值积分方法的舍入误差概率分布函数以及截断误差积累量对步长的依赖关系和随时间的增长关系进行了深入研究. 基于所得结论, 提出了一种仅需较少的数值实验资料即可对选择任意时间步长积分至任意积分时刻时的舍入误差概率分布函数与截断误差积累量进行准确估计的方法, 并使用Adams-Cowell方法对该误差估计方法在圆周期轨道条件下进行了验证. 该误差估计方法在未来有望用于不同数值算法的性能对比研究, 同时也可以对数值积分方法求解实际轨道问题时的决策工作带来重要帮助.     

一种载人小行星探测轨道优化设计方法

给出了一种基于变比冲核电推进载人飞船探测小行星的轨道优化设计方法.首先基于双脉冲单圈Lambert轨道转移,对地球出发段和返回段进行搜索剪枝,再从两个可行区域中优选最佳飞行路径.设定"推进-滑行-推进"的分段飞行策略,以工质消耗最少为指标,利用混合法优化核电推进飞行轨迹,最后以分段优化参数为初值,基于整体任务约束将全飞行过程转化为非线性优化问题,将各飞行段进行拼接,获得整体参数优化解,并给出了数值和图形结果.     

活动小行星311P/PANSTARRS的动力学lk 特性分析

311P/PANSTARRS是一颗活动小行星, 具有小行星和彗星的双重特征, 是中国``天问二号''的探测目标之一. 311P/PANSTARRS直径较小, 约为400 m, 非引力效应可能会对其长期动力学演化产生较大的影响. 通过假定不同表面组分, 研究了Yarkovsky效应对311P/PANSTARRS轨道演化的影响, 讨论了密近交汇、 非破坏性碰撞和YORP (Yarkovsky-O''Keefe-Radzievskii-Paddack)效应等非引力效应, 计算了小行星与大行星密近交汇及碰撞概率, 估计了311P/PANSTARRS达到自转周期分裂极限的时标. 模拟结果显示与纯引力模型相比, Yarkovsky效应可能会加快311P/PANSTARRS离开当前共振区域, 大约在10Myr以后311P/PANSTARRS会离开当前所在共振带, 在表面覆盖风化层的情况下有机会通过v6长期共振成为越火小行星; 在考虑YORP效应的情况下, 311P/PANSTARRS在2 Myr时标内可达到自转周期分裂极限; 在考虑Yarkovsky效应及YORP效应等因素的情况下, 311P/PANSTARRS在10 Myr时标内仍可保持其动力学稳定性, 且YORP效应不会显著影响其半长径偏移量.     

主带小行星深空探测可接近性与多目标探测轨道的实现

小行星探测是当前深空探测的热点之一,探测目标的可接近性又是探测任务首先要解决的问题.根据直接转移轨道方式下太阳系中可以探测到的区域和小行星的空间分布,确认发射能量C_3=50 km~2/s~2的直接转移轨道,可以探测大部分主带小行星;使用少量的速度修正还能够实现多目标飞越任务.同时指出,这种多目标的飞越可以达到△V-EGA轨道方案中的深空机动同样的效果,经地球引力助推,以较小能量实现小行星伴飞或更遥远小行星的探测;据此提出了一个探测器先飞越多颗主带小行星,然后借助地球引力助推探测更遥远小行星的轨道设计方案,并给出了设计实例.     

小行星Icarus激光测距空间任务科学价值的研究

小行星Icarus激光测距空问任务是在第1566号小行星上放置激光反射器、定时器并与地面站之间进行激光干涉测距,对PPN参数γ和β、太阳四极矩J2、万有引力常数的时间变化率G/G和太阳系天体的质心引力常数进行精确测量.随着激光技术的发展,10ps(用测距量表示是3mm)的计时精度是可以实现的.2015年Icarus与地球接近,为Icarus着陆器提供了良好的发射窗口.本文采用PMOE 2003行星历表框架,从2015年9月25日起,对地面站和小行星之间的激光测距进行了为期800天的模拟,应用Kalmam滤波方法,得到18个参数的不确定度,其中γ,β、J2和G/G的不确定度分别为7.8×10-8、9.0×10-7,9.8×10-11和7.0×10-15yr-1,均高于现有实验的精度1-3个数量级.模拟结果表明,这个空间任务对相对论的检验、太阳系基本参数的测定、以及时空基本定律的检验等都有重要的科学意义.     

相互逼近技术用于小行星702(Alauda)的高精度位置测量试验

将相互逼近(Mutual Approximation)技术从天然卫星的天体位置测量拓展到小行星和邻近盖亚(Gaia)星表参考星的相对位置测量,希望获得更高的小行星位置测量精度.使用中国科学院云南天文台1 m光学望远镜在2020年11月11～12日对小行星702(Alauda)进行了观测试验.在观测资料中,目标小行星共有...     

卫星轨道确定模型误差的深度加权核估计方法

卫星动力学模型误差是客观存在的事实,动力学模型误差传递到轨道确定算法中构成部分形式未知的模型误差,并且与测量系统自身的系统误差和随机误差耦合在一起形成定轨模型误差,严重影响轨道确定精度.详细推导了存在动力学模型误差的轨道改进方程,对模型中能准确描述的部分建立了参数化模型,对不能准确描述的误差部分,建立了非参数模型.构建了部分线性轨道改进模型,利用二阶段估计法和核函数估计法对模型误差进行拟合估计,并在轨道改进中予以补偿.根据数据深度理论,建立了非参数模型误差的深度加权核估计方法,提高了模型误差估计的抗差性.最后结合天基空间目标监视系统进行了轨道确定仿真实验.实验结果表明,模型误差是影响轨道确定精度的重要因素,核函数估计法可以有效估计定轨中的模型误差,窗宽是提高模型估计精度的重要变量,通过深度加权处理可以明显提高核函数估计的抗差性,提高轨道确定精度.     

基于GRACE数据的西南陆地水储量分析

利用地球重力卫星GRACE(Gravity Recovey and Climate Experiment)2005年1月～2010年4月期间64个月的数据,对我国西南地区陆地水储量变化进行了反演.结果表明,选取适当的高斯半径(R=600 km)和所采用数据的平均引力场作为背景引力场,则基于GRACE数据反演的西南陆地水...     

Orbit Determination of the Asteroid (469219) Kamoòalewa and Its Error Analysis

As an Earth co-orbital asteroid, (469219) Kamoòalewa is a near earth object (NEO) with high value of research, and one of the targets explored by the first Chinese asteroid exploration mission. Given its orbit characteristics, we build a refined dynamical model for this asteroid, in which the effects induced by nonspherical gravitational fields of the Sun, the Earth, and the Moon are combined. On the basis of the dynamical model of the asteroid (469219) Kamoòalewa, its orbit is determined with optical data from 2004 to 2018 available on the Minor Planet Center (MPC) database. The root mean square error of post-fit residuals is about 0.2 arc second (comparable with that of the Jet Propulsion Laboratory (JPL)/Horizons), and the post-fit residuals of optical observations in 2004 are decreased. At the end, we implement error analysis on the asteroid (469219) Kamoòalewa's orbit in detail, and also predict its orbit error at the time interval between 2020 and 2025.     

A Statistical Analysis on the Color and Orbit Parameters of Centaurs

In order to study the statistical characters and physical significance of the color indexes and orbital parameters of Centaurs, we have analyzed the color and orbit parameter correlations by using statistical methods according to the known color indexes of 39 Centaurs and their respective orbital parameters. We find that all the correlations of B − V vs. V − R, V − R vs. R − I, B − V vs. R − I and B − R vs. R − I are strong. The Centaurs exhibit obvious redblue double-color property, and the point of demarcation is close to B − R = 1.4. The distributions of the various color indexes of Centaurs exhibit the normal distribution. For the correlations between colors and orbital parameters, except for the weak correlations between B − V and the orbital inclination i as well as between V − R and the orbital semi-major axis a, no evident correlation has been found between color indexes and orbital parameters.     

Scientific Value of the Laser Ranging of Asteroid Icarus

The space mission of the laser ranging of asteroid Icarus is that a laser reflector and a timer are placed on the No.1566 asteroid and the laser interference ranging is conducted between the asteroid and the ground-based station for making the precise measurements of the PPN parameters γ and β, solar quadrupolar moment J₂, time rate of change ?/G of the gravitational constant and barycentric gravitational constant of the solar system objects. With the development of laser techniques, the timing accuracy of 10 ps (or 3 mm expressed by the amount of ranging) can be realized. In 2015 the asteroid Icarus will be close to the earth, which provides a better launch window for the Icarus lander. In the present article the 2003 interplanetary ephemeris frame of the PMOE is adopted to simulate the laser ranging between the ground-based station and the asteroid for 800 days from 2015 September 25 on and obtain the indeterminacies of 18 parameters, among which those of γ, β, J₂ and ?/G are respectively 7.8 × 10⁻⁸, 9.0 × 10⁻⁷, 9.8 × 10⁻¹¹ and 7.0 × 10−15yr⁻¹, with each being 1 to 3 orders higher than the available experimental accuracy. The simulated result shows that this space mission is of scientific significance to the test of the theory of relativity, determination of the fundamental parameters of solar system and test of the space-time fundamental laws.     

The Data Depth-weight-kernel Estimation of the Model Error of Satellite Orbit Determination

It is an objective fact that there exists error in the satellite dynamic model and it will be transferred to satellite orbit determination algorithm, forming a part of the connotative model error. Mixed with the systematic error and random error of the measurements, they form the unitive model error and badly restrict the precision of the orbit determination. We deduce in detail the equations of orbit improvement for a system with dynamic model error, construct the parametric model for the explicit part of the model and nonparametric model for the error that can not be explicitly described. We also construct the partially linear orbit determination model, estimate and fit the model error using a two-stage estimation and a kernel function estimation, and finally make the corresponding compensation in the orbit determination. Beginning from the data depth theory, a data depth weight kernel estimator for model error is proposed for the sake of promoting the steadiness of model error estimation. Simulation experiments of SBSS are performed. The results show clearly that the model error is one of the most important effects that will influence the precision of the orbit determination. The kernel function method can effectively estimate the model error, with the window width as a major restrict parameter. A data depth-weight-kernel estimation, however, can improve largely the robustness of the kernel function and therefore improve the precision of orbit determination.     

Orbit of comet C/1860 M1 (Great Comet of 1860)

Comet C/1860 M1 (Great Comet of 1860) is one of a large number of comets with parabolic orbits. Given that there are sufficient observations of the comet, 261 in right ascension and 251 in declination, it proves possible to calculate a better orbit. The comet's orbit is hyperbolic, and statistically different from a parabola. The comet, therefore, cannot be considered to be a Near Earth Oject. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Asteroid orbits using phase-space volumes of variation

We present a statistical orbit computation technique for asteroids with transitional observational data, that is, a moderate number of data points spanning a moderate observational time interval. With the help of local least-squares solutions in the phase space of the orbital elements, we map the volume of variation as a function of one or more of the elements. We sample the resulting volume using a Monte Carlo technique and, with proper weights for the sample orbital elements, characterize the six-dimensional orbital-element probability density function. The volume-of-variation (VOV) technique complements the statistical ranging technique for asteroids with exiguous observational data (short time intervals and/or small numbers of observations) and the least-squares technique for extensive observational data. We show that, asymptotically, results using the new technique agree closely with those from ranging and least squares. We apply the technique to the near-Earth object 2004 HA₃₉, the main-belt object 2004 QR and the transneptunian object 2002 CX₂₂₄ recently observed at the Nordic Optical Telescope on La Palma, illustrating the potential of the technique in ephemeris prediction. The VOV technique helps us assess the phase transition in orbital-element probability densities, that is, the non-linear collapse of wide orbital-element distributions to narrow localized ones. For the three objects above, the transition takes place for observational time intervals of the order of 10 h, 5 d and 10 months, respectively, emphasizing the significance of the orbital-arc fraction covered by the observations.     

干支回推-天文年代学的一种新方法

“干支回推法”是针对中国历史时期所特有的干支材料而设计的新天文年代学方法．以一组假设的材料为例,系统地给出了该方法的完整求解过程．指出该方法的优势在于准确高效,能有效地处理某些年代学难题．此外,除材料的公历日期外还能将当时的历法细节一同迭代解出．