星载GPS自主定轨的长期稳定性

通过模拟长达100天的星载GPS伪距观测资料,进行卡尔曼滤波定轨仿真计算．重点研究：1)采用简化的动力学模型与简化状态转移矩阵,是否保证滤波的长期稳定性；2)模型误差矩阵Q的选取对滤波定轨精度的影响；3)与事后最小二乘批处理相比较,在简化模型下自主定轨的精度．同时给出了相应的结论．     

双星轨道拟合的研究进展

双星轨道拟合是天文学的一项基础性研究工作。其主要目的是给出双星系统的二体轨道参数,这些参数不仅是高精度、高网格密度星表参考架的必要组成部分,而且也为理解各种有关观测现象提供了必要的动力学基础;更重要的是,双星轨道拟合可以直接估计恒星物理和星系天文学等领域极有应用价值的恒星质量参数。因此,长期以来双星轨道拟合工作一直受到研究者的广泛关注。近年来,随着高精度的恒星运动学观测资料的大量积累,双星轨道拟合更成为天体测量和天体力学的一个共同的热点课题,有关研究也有了长足的进展。综述了双星轨道拟合的历史及现状,其中着重介绍了目前所用的主要观测资料和各种具体的拟合模型、拟合方法;简要描述了几种主要的双星星表;展望了今后双星轨道拟合工作的发展趋势。     

Symmetries and Rank Deficiency in the Orbit Determination Around Another Planet

We study the possible degeneracies for the normal matrix of the observations from the Earth of the motion of a satellite around a planet, and give the possible solutions to the loss of precision in the orbit determination caused by the rank deficiency. Finally we discuss the methods available to control the instability in the orbit determination resulting from the degeneracy.     

Lambert problem solution in the hill model of motion

The goal of this paper is obtaining a solution of the Lambert problem in the restricted three-body problem described by the Hill equations. This solution is based on the use of pre determinate reference orbits of different types giving the first guess and defining the sought-for transfer type. A mathematical procedure giving the Lambert problem solution is described. This procedure provides step-by-step transformation of the reference orbit to the sought-for transfer orbit. Numerical examples of the procedure application to the transfers in the Sun–Earth system are considered. These examples include transfer between two specified positions in a given time, a periodic orbit design, a halo orbit design, halo-to-halo transfers, LEO-to-halo transfer, analysis of a family of the halo-to-halo transfer orbits. The proposed method of the Lambert problem solution can be used for the two-point boundary value problem solution in any model of motion if a set of typical reference orbits can be found.     

稳健估计在轨道改进中的应用

通过对20颗卫星的模拟计算，研究了人造卫星光学观测的轨道改进方法，给出了资料预处理(观测精度σ0=5″)的剔除门限，使野值的比例在大多数情况下小于10％；在轨道改进中，先用Huber估计迭代2次，再用Hampel估计迭代到收敛，保证了轨道改进的精度；重点研究了Hampel估计的权函数参数(C0，C1，C2)的取值，得出结论：对于大于或等于6σ0的野值，C0可取为2．2，C1可取为3．6，C2的取值和野值大小有关．     

卫星轨道预报的一种分析方法

人造地球卫星的轨道预报是空间环境监测和实时跟踪测量中一个重要环节，由于监测对象众多，要求精度也不太高，通常采用分析法预报．在已有分析法得到t时刻平均根数的基础上给出一种轨道预报方法，由t时刻的平均根数给出该时刻卫星的位置和速度，在此基础上将地球非球形引力摄动的周期项直接用卫星直角坐标的位置和速度分量表示，这样可以避免在计算轨道根数变化的周期项时出现的奇点问题，从而对根数的选择无特殊要求，可适用于各种轨道，简化预报程序和相应的软件，提高预报效率。     

Behaviour of the SMF method for the numerical integration of satellite orbits

The SMF algorithms were recently developed by the authors as a multistep generalization of the ScheifeleG-functions one-step method. Like the last, the proposed codes integrate harmonic oscillations without truncation error and the perturbing parameter appears as a factor of that error when integrating perturbed oscillations. Therefore they seemed to be convenient for the accurate integration of orbital problems after the application of linearizing transformations, such as KS or BF. In this paper we present several numerical experiments concerning the propagation of Earth satellite orbits, that illustrate the performance of the the SMF method. In general, it provides greater accuracy than the usual standard algorithms for similar computational cost.     

精密定轨用地球大气模型误差的补偿方法

本文提出了一种用于精密轨道确定的地球大气模型误差的补偿方法，这种方法采用改进 大气周日峰角的技术，有效地补偿了大气密度模型的误差，并具有较好的物理意义．与传统 的每圈改进一次加速度的方法比较，轨道确定达到了相当的径向精度，且避免了轨道改进参 数间的相关性，同时解算参数的数量也少了一半．     

A survey of orbits of co-orbitals of Mars

Many asteroids with a semimajor axis close to that of Mars have been discovered in the last several years. Potentially some of these could be in 1:1 resonance with Mars, much as are the classic Trojan asteroids with Jupiter, and its lesser-known horseshoe companions with Earth. In the 1990s, two Trojan companions of Mars, 5261 Eureka and 1998 VF₃₁, were discovered, librating about the L₅ Lagrange point, 60° behind Mars in its orbit. Although several other potential Mars Trojans have been identified, our orbital calculations show only one other known asteroid, 1999 UJ₇, to be a Trojan, associated with the L₄ Lagrange point, 60° ahead of Mars in its orbit. We further find that asteroid 36017 (1999 ND₄₃) is a horseshoe librator, alternating with periods of Trojan motion. This asteroid makes repeated close approaches to Earth and has a chaotic orbit whose behavior can be confidently predicted for less than 3000 years. We identify two objects, 2001 HW₁₅ and 2000 TG₂, within the resonant region capable of undergoing what we designate “circulation transition”, in which objects can pass between circulation outside the orbit of Mars and circulation inside it, or vice versa. The eccentricity of the orbit of Mars appears to play an important role in circulation transition and in horseshoe motion. Based on the orbits and on spectroscopic data, the Trojan asteroids of Mars may be primordial bodies, while some co-orbital bodies may be in a temporary state of motion.