共查询到20条相似文献，搜索用时 626 毫秒
1.
Alessandra Celletti Gabriella Pinzari 《Celestial Mechanics and Dynamical Astronomy》2005,93(1-4):1-52
The discovery of the asteroid Ceres by Piazzi in 1801 motivated the development of a mathematical technique proposed by Gauss,
(Theory of the Motion of the Heavenly Bodies Moving about the Sun in Conic Sections, 1963) which allows to recover the orbit
of a celestial body starting from a minimum of three observations. Here we compare the method proposed by Gauss (Theory of
the Motion of the Heavenly Bodies Moving about the Sun in Conic Sections, New York, 1963) with the techniques (based on three
observations) developed by Laplace (Collected Works 10, 93–146, 1780) and by Mossotti (Memoria Postuma, 1866). We also consider
another method developed by Mossotti (Nuova analisi del problema di determinare le orbite dei corpi celesti, 1816–1818), based
on four observations. We provide a theoretical and numerical comparison among the different procedures. As an application,
we consider the computation of the orbit of the asteroid Juno. 相似文献
2.
经典的初轨确定方法包括Laplace方法和Gauss方法以及它们的各种变化形式. 除这些经典方法之外, 基于当今光学观测数据的特点, 学者们也陆续提出了一些其他的初轨确定方法, 包括双r (目标距离观测者的距离)方法和可行域方法. 双r方法的一种实现方式是通过猜测某两个时刻(通常是定轨弧段的首、末时刻)目标离观测者的距离, 结合观测者在空间中的位置矢量, 即可求解相应的Lambert弧段作为目标轨道的初始猜测. 进一步, 以其他观测时刻的RMS (Root Mean Square)为优化变量可以改进初始猜测从而确定初轨. 可行域方法则是针对一组初始观测参数(包括赤经、赤纬及其变率), 根据一些初始假设将目标(离观测者的)距离及其变率约束在可行域内, 并通过三角划分逐步逼近的方式寻找到使观测RMS最小的猜测解. 针对一系列模拟观测数据以及实测数据, 将智能优化算法(粒子群算法)应用于这两种初轨方法, 并将结果与改进的Laplace算法的结果进行比较. 由于双r方法不仅可以用于短弧定轨还可用于长弧关联, 所以进一步给出了针对长弧段数据的关联结果. 相似文献
3.
《New Astronomy》2022
In this paper, we study the weak deflection angle in the spacetime of improved Schwarzschild black hole using the method derived by Gibbons and Werner. To do so, we derive the optical curvature from the optical metric and calculate deflection angle in weak field limits by using the Gauss–Bonnet theorem. Moreover, we study the effect of the plasma medium on the weak gravitational lensing using the Gauss–Bonnet theorem. Furthermore, we also study the graphical analysis of the deflection angle in both the plasma and non-plasma mediums. Moreover, we obtain the bound on greybody for improved Schwarzschild black hole. 相似文献
4.
5.
LP估计在星载GPS运动学定轨中的应用及精度分析 总被引：2，自引：0，他引：2
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． 相似文献
6.
We describe the application of the implicit midpoint integrator to the problem of attitude dynamics for low-altitude satellites without the use of quaternions. Initially, we consider the satellite to rotate without external torques applied to it. We compare the numerical solution with the exact solution in terms of Jacobi’s elliptic functions. Then, we include the gravity-gradient torque, where the implicit midpoint integrator proves to be a fast, simple and accurate method. Higher-order versions of the implicit midpoint scheme are compared to Gauss–Legendre Runge–Kutta methods in terms of accuracy and processing time. Finally, we investigate the performance of a parameter-adaptive Kalman filter based on the implicit midpoint integrator for the determination of the principal moments of inertia through observations. 相似文献
7.
Davide Farnocchia Giacomo Tommei Andrea Milani Alessandro Rossi 《Celestial Mechanics and Dynamical Astronomy》2010,107(1-2):169-185
We propose two algorithms to provide a full preliminary orbit of an Earth-orbiting object with a number of observations lower than the classical methods, such as those by Laplace and Gauss. The first one is the Virtual debris algorithm, based upon the admissible region, that is the set of the unknown quantities corresponding to possible orbits for a given observation for objects in Earth orbit (as opposed to both interplanetary orbits and ballistic ones). A similar method has already been successfully used in recent years for the asteroidal case. The second algorithm uses the integrals of the geocentric 2-body motion, which must have the same values at the times of the different observations for a common orbit to exist. We also discuss how to account for the perturbations of the 2-body motion, e.g., the J 2 effect. 相似文献
8.
In this paper, we deal with the stellar three body problem, that is one star is far away from the other two stars. The outer
orbit is assumed to be Keplerian. To analyze the effect of the distant star on the orbit of the close stars, we use the Gauss
method; this method consist in replacing the gravitational attraction of the third star by the gravitational attraction of
an infinitesimal non-homogeneous elliptic ring. We obtain the force vector for the Gauss method in terms of elliptic integrals.
Finally we compare the results obtained by this model with the classical third body model.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
10.
The asteroseismic observations provided by current and future missions like CoRoT or Kepler will have a quality closer to those obtained for the Sun. In this context, tools and methods developed for helioseismology can be applied to other stars. In this paper, we focus on solar‐like oscillations of stars with an unknown rotation axis inclination and study, by means of maximum‐likelihood estimation, the errors on the determination of l = 1 p‐mode parameters. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
11.
Maciej Konacki Andrzej J. Maciejewski 《Monthly notices of the Royal Astronomical Society》1999,308(1):167-179
We analyse different methods of searching for planets around neutron stars by timing observations of pulsars. To this end, we study a few interesting models describing TOA residual variations that are observed, or could be observed, and which can mimic planets. We carry out a detailed theoretical analysis of the behaviour of these methods in the situations mentioned. We show that it is very helpful to look at these phenomena as some kind of quasi-periodic variations of residuals of time of arrival of pulsar pulses. We demonstrate that such a model-independent approach leads to promising conclusions that can be useful when analysing timing observations of pulsars to find planets or to prove that observed phenomena are of planetary origin. 相似文献
12.
13.
14.
J. R. Touma S. Tremaine M. V. Kazandjian 《Monthly notices of the Royal Astronomical Society》2009,394(2):1085-1108
We show that the algorithm proposed by Gauss to compute the secular evolution of gravitationally interacting Keplerian rings extends naturally to softened gravitational interactions. The resulting tool is ideal for the study of the secular dynamical evolution of nearly Keplerian systems such as stellar clusters surrounding black holes in galactic nuclei, cometary clouds or planetesimal discs. We illustrate its accuracy, efficiency and versatility on a variety of configurations. In particular, we examine a secularly unstable system of counterrotating discs, and follow the unfolding and saturation of the instability into a global, uniformly precessing, lopsided ( m = 1) mode. 相似文献
15.
16.
天王星卫星的CCD观测与分析解的比对 总被引：2，自引：0，他引：2
本文给出了处理天王星卫星ＣＣＤ图象位置资料的新方法,并将我们在１９９５年取得的重要资料与两种理论模型位置进行了比较计算,结果表明经处理后的天王星五颗主要卫星ＣＣＤ观测精度有了较大提高。 相似文献
17.
A model for the solar dynamo, consistent in global flow and numerical method employed with the differential rotation model, is developed. The magnetic turbulent diffusivity is expressed in terms of the entropy gradient, which is controlled by the model equations. The magnetic Prandtl number and latitudinal profile of the alpha-effect are specified by fitting the computed period of the activity cycle and the equatorial symmetry of magnetic fields to observations. Then, the instants of polar field reversals and time-latitude diagrams of the fields also come into agreement with observations. The poloidal field has a maximum amplitude of about 10 Gs in the polar regions. The toroidal field of several thousand Gauss concentrates near the base of the convection zone and is transported towards the equator by the meridional flow. The model predicts a value of about 1037 erg for the total magnetic energy of large-scale fields in the solar convection zone. 相似文献
18.
Modern asteroid surveys produce an increasingly large number of observations, which are grouped into very short arcs (VSAs) each containing a few observations of the same object in one single night. To decide whether two VSAs collected in different nights correspond to the same observed object we can attempt to compute an orbit with the observations of both arcs: this is called the linkage problem. Since the number of linkages to be attempted is very large, we need efficient methods of orbit determination. Using the first integrals of Kepler’s motion we can write algebraic equations for the linkage problem, which can be put in polynomial form. In Gronchi et al. (Celest Mech Dyn Astron 123(2):105–122, 2015) these equations are reduced to a polynomial equation of degree 9: the unknown is the topocentric distance of the observed body at the mean epoch of one VSA. Here we derive the same equations in a more concise way, and show that the degree 9 is optimal in a sense that will be specified in Sect. 3.3. We also introduce a procedure to join three VSAs: from the conservation of angular momentum we obtain a polynomial equation of degree 8 in the topocentric distance at the mean epoch of the second VSA. For both identification methods, with two and three VSAs, we discuss how to discard solutions. Finally, we present some numerical tests showing that the new methods give satisfactory results and can be used also when the time separation between the VSAs is large. The low polynomial degree of the new methods makes them well suited to deal with the very large number of asteroid observations collected by the modern surveys. 相似文献
19.
《天文和天体物理学研究(英文版)》2016,(4)
The anisotropies of the B-mode polarization in the cosmic microwave background radiation play a crucial role in the study of the very early Universe. However, in real observations, a mixture of the Emode and B-mode can be caused by partial sky surveys, which must be separated before being applied to a cosmological explanation. The separation method developed by Smith(2006) has been widely adopted,where the edge of the top-hat mask should be smoothed to avoid numerical errors. In this paper, we compare three different smoothing methods and investigate leakage residuals of the E-B mixture. We find that, if less information loss is needed and a smaller region is smoothed in the analysis, the sin- and cos-smoothing methods are better. However, if we need a cleanly constructed B-mode map, the larger region around the mask edge should be smoothed. In this case, the Gaussian-smoothing method becomes much better. In addition, we find that the leakage caused by numerical errors in the Gaussian-smoothing method is mostly concentrated in two bands, which is quite easy to reduce for further E-B separations. 相似文献
20.
We estimate the effect of trajectory measurement errors on the orbital parameters of asteroid Apophis determined from improvements. For this purpose, based on all of the optical and radar observations available to date, we have computed a nominal orbit of the asteroid. The scatter ellipsoid of the initial conditions of motion has been obtained by two methods. In the first, universally accepted method, the scatter ellipsoid is calculated by assuming a linear dependence of the errors in the parameters being determined on observational errors. In the second method, the scatter region of the orbital parameters around the nominal-orbit parameters is determined by the Monte Carlo method. We show that the region determined by the latter method at the initial epoch differs only slightly from the scatter ellipsoid for the linear approximation. We estimate the sizes of the projections of the corresponding regions onto the target plane at the time of the closest encounter of the asteroid with the Earth in 2029. The projections are approximated by ellipses. Our computations have shown that the ellipse has the following sizes: 389.6 km for the semimajor axis and 16.4 km for the semiminor axis in the linear case and 330.0 and 11.1 km, respectively, in the nonlinear case. 相似文献