LP估计在星载GPS运动学定轨中的应用及精度分析

为得到高精度的星载GPS运动学定轨,必须利用观测精度高的相位观测值,但是相位观测值预处理后,仍然存在残余小周跳．在残差服从正态分布情况下LS法是最佳参数解算方法,但该方法不能解决资料的系统误差消除问题,LP估计是处理资料残差分布含有系统误差的有效方法之一．基于LS、LP方法的有效条件和GPS数据预处理的特性,将LP估计方法引入星载GPS运动学定轨数据处理中,以CHAMP卫星资料为例,研究了LP估计在星载GPS运动学定轨中的应用及其精度分析．实践表明:在处理含有残余小周跳的相位观测值时,LP估计比LS更有效,提高了星载GPS运动学定轨精度,但随着残余周跳的进一步修复,LP估计相对于LS估计的优越性越来越弱,在资料完全没有系统误差,残差服从正态分布的情况下,LP估计不能很好地体现其优越性,精度反而低于LS估计．     

On derivation of EIH (Einstein–Infeld–Hoffman) equations of motion from the linearized metric of general relativity theory

The half-century old idea of Infeld to use the variational principle of the general relativity field equations is reminded to show that the commonly employed EIH (Einstein–Infeld–Hoffman) equations of motion may be derived from the linearized (weak-field) metric alone. Based on it, the linearized metric might be sufficient for post-Newtonian celestial mechanics and astrometry enabling one to derive the post-Newtonian equations of motion and rotation of celestial bodies as well as the post-Newtonian equations of light propagation within the general relativity framework.     

单站单圈测距资料初轨计算的单位矢量法

根据单位矢量法测轨原理，在已知轨道面参数i，Ω的前提下，给出了一种适用于单站单圈测距资料的初轨计算方法．计算结果表明，方法是有效的．在没有测角资料或测角资料精度显著低于测距精度的情况下，有应用价值．     

Determination of an intermediate perturbed orbit from three position vectors

We suggest a new approach to solving the problem of finding the orbit of a celestial body from its three spatial position vectors and the corresponding times. It allows most of the perturbations in the motion of a celestial body to be taken into account. The approach is based on the theory of intermediate orbits that we developed previously. We construct the orbit the motion along which is a combination of two motions: the motion of a fictitious attracting center whose mass varies according to Mestschersky’s first law and the motion relative to the fictitious center. The first motion is generally parabolic, while the second motion is described by the equations of the Gylden-Mestschersky problem. The constructed orbit has such parameters that their limiting values at any reference epoch define a superosculating intermediate orbit with a fourth-order tangency. We have performed a numerical analysis to estimate the accuracy of approximating the perturbed motion of two minor planets, 145 Adeona and 4179 Toutatis, by the orbits computed using two-position procedures (the classical Gauss method and the method that we suggested previously), a three-position procedure based on the Herrick-Gibbs equation, and the new method. Comparison of the results obtained suggests that the latter method has an advantage.     

Effect of perturbation of coriolis and centrifugal forces on the location and linear stability of the libration points in the robe problem

The locations and linear stability of the main libration points in Robe's restricted three-body problem under perturbed Coriolis and centrifugal forces are investigated. The perturbed locations of these points are given. The perturbation magnitude of their locations and linear stability are estimated. The results obtained by Shrivastava and Garain^[10] are improved.     

Using long-term transit timing to detect terrestrial planets

We propose that the presence of additional planets in extrasolar planetary systems can be detected by long-term transit timing studies. If a transiting planet is on an eccentric orbit then the presence of another planet causes a secular advance of the transiting planet's pericentre over and above the effect of general relativity. Although this secular effect is impractical to detect over a small number of orbits, it causes long-term differences when future transits occur, much like the long-term decay observed in pulsars. Measuring this transit-timing delay would thus allow the detection of either one or more additional planets in the system or the first measurements of non-zero oblateness ( J ₂) of the central stars.     

倾角函数的四精度计算试验

倾角函数是天体力学分析理论中一种常用的函数.当把摄动方程展开成时间和根数的形式时需要用到.历史上提出了很多经典的倾角函数递推算法,并在双精度平台下开发了Fortran程序.进行了1次四精度计算倾角函数的试验,结果表明:L平面递推方法的四精度计算精度可达10-22,计算速度比双精度Jacobi方法快6倍.