共查询到19条相似文献，搜索用时 390 毫秒
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采用通过中国科学院国家授时中心(NTSC)GPS单、双频这2类观测设备得到的实测数据,进行了NTSC—PTB(physikalisch-technische bundesanstalt(Germary))链路的全视法比对计算和分析。利用这2类设备得到的GPS AV(全视)的结果与BIPM公布的AV方法的A类不确定度一致,从而确定国家授时中心的2类GPS观测设备的性能达到了国际同类水平。如果对双频观测设备时延校准后,采用P3类型进行比对,有望将NTSC现有的比对精度提高50%。 相似文献
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运用在brick-wall方法的基础上发展起来的薄膜模型计算了六维动态黑洞的自由能和玻色子熵，然后应用Г矩阵方法计算了费米子熵．结果显示六维动态黑洞的玻色子熵和费米子熵有相同的形式，它们之间只相差一个系数．并且仍然满足Bekenstein-Hawking的熵与面积的关系． 相似文献
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用球谐函数方法（SHM）计算了由Schwiderski海潮图和日本海海潮图引起的M2,S2,K1和O1各分潮波的综合海潮负荷参数.计算中采用了Pagiatakis（1990）地球模型的负荷Love数.结果表明SHM具有更高的计算效率和计算精度．为了真正实现±毫米的VLBI地壳运动测定精度和±0.1微伽的绝对重力测量精度,对未来海潮图模型,特别是日本海的海潮图模型的精度要求作了讨论．计算结果还表明不同地球模型的负荷Love数对计算的测站位移之差为0.7毫米,在目前测量精度下尚可以不作考虑.中国近海的海潮M2波对台北,上海,Daejeon,Okinawa,和Kagosima站的径向和水平分量位移影响可分别达±22．4～±1．0毫米和±05-±5.5毫米,表明中国近海高精度的海潮图模型对东亚测站的地壳运动高精度测量是十分重要的． 相似文献
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黄润乾 《中国天文和天体物理学报》1999,(2)
现今双星演化理论中,以子星的半径等于临界洛希瓣半径,作为双星中发生物质交换过程的判据,仅仅是一个为了将三维计算简化为一维计算而引入的近似判据．它在理论上是不严格的．本文给出了一个理论严格而又能一维计算的判据．并用新的判据和用子星半径等于临界洛希瓣半径的判据,对一个由９Ｍ和６Ｍ恒星组成的双星系统,进行了情况Ａ的演化计算（即物质交换过程发生在主星中心氢燃烧阶段）．结果证明,用新的判据时,双星中发生物质交换过程的起始时间提前,快速物质交换过程变短,平均物质交换率增大,但慢速物质交换过程变长．在物质交换过程结束时,主星和次星的质量、双星系统的轨道周期以及主星在赫罗图中的位置,都与采用子星半径等于相应洛希瓣半径作为判据的计算结果明显不同．这说明,发生物质交换过程的判据是否严格,对于双星演化的影响是不可忽略的． 相似文献
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首先指出目前星风吸积模型中理论上的不自洽，考虑到δｒ≠０，重新推导轨道参量变化方程，消去了理论上的不自洽．提出一个新模型：首次将星风吸积同内禀ＡＧＢ星核合成模型结合起来计算钡（Ｂａ）星的重元素超丰，并将计算结果与观测值进行了比较．各参量按标准情况取值时，计算结果不太理想．取Ｂｏｎｄｉｈｏｙｌｅ吸积率的０．５倍或取较大的星风速率时，对于较长轨道周期（Ｐ＞１０００天）的Ｂａ星，计算结果与观测值基本符合；而较短轨道周期（Ｐ＜６００天）的Ｂａ星，其重元素超丰机制可能是盘吸积 相似文献
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外赋AGB星星风吸积的角动量守恒模型 总被引：5，自引：0，他引：5
用整个系统的角动量守恒条件代替切向动量守恒条件,推导出星风质量吸积及轨道参量变化方程．在新的轨道参量变化方程的基础上,计算了外赋AGB星系统的星风质量吸积及轨道参量的变化．将星风吸积模型同内禀AGB星核合成模型结合起来,通过逐次脉冲吸积质量和混合,自洽地计算外赋AGB星的重元素超丰,并给出计算结果与观测值的比较．对初始质量较大的Ba星（M2．0＝2．5M⊙）,当系统轨道周期大于1300天时,属于星风吸积,小于600天成为共同包层双星或灾变双星．对初始质量较小的Ba星（M2．0＝13M⊙）,当系统轨道周期大于1600天时,属于星风吸积,小于600天时成为灾变双星,由此可以解释Ba星的重元素超丰和轨道参量的观测事实,并有利于解释观测到的外赋S星轨道周期的600天下限．随着星风吸积过程的进行,轨道偏心率逐渐增大,这对解释Ba星轨道偏心率平均值大于外赋S星和CH星平均值的观测事实有利． 相似文献
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利用一种非定常的恒星非局部对流理论,对球状星团中低光度的红巨星进行了线性非绝热脉动理论计算．结果表明,对所有温度高于约5400 K模型的基音到4阶泛音都是脉动稳定的．随着恒星光度的增大,低阶泛音也变得脉动不稳定．对中低光度的红巨星,脉动稳定性非常低,接近中性稳定．因此他们将是不变星或非常小振幅的短周期变星(P<2天)． 相似文献
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Chen Wu-shen Zhang Jing Ma Jing-yuan Lu Ben-kui 《Chinese Astronomy and Astrophysics》2006,30(4):431-436
Based on the analysis of the characteristics of the equations of condition in the UVM2 (Unit Vector Method 2), the total least squares method (TLS) is introduced into the orbital determination and the linearization of the vis-viva formula in the original algorithm is thereby avoided. The calculated results from simulation and observation data show that the application of TLS to UVM2 is effective. 相似文献
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From the point of view of the non-parametric statistics, a general estimation method of the accuracy and con?dence interval of preliminary orbit determination is proposed for the occasion without any other information but observational data. Based on the bootstrap method, the estimation relies only on the observational data and does not require the precise orbit determination as a reference, or the assumption of normal distribution of observational errors. Numerical experiments show that this method is very simple in implementa- tion, and may serve as an easy accuracy evaluation for the preliminary orbit determination and for the follow-up employments. 相似文献
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V. B. Kuznetsov 《Solar System Research》2012,46(2):136-143
A modification of the Laplace method for the determination of a preliminary orbit of a body moving in the plane of the ecliptic
is presented. It is shown that on the basis of three close positions on the celestial sphere, the parabolic orbit can be determined
in cases, when the classical Laplace method is not suitable. The numerical estimation of the number of possible solutions
is carried out, and their spatial distribution depending on initial conditions is shown. An example of the determination of
an orbit for the comet C/2007 N3 (Lulin) is given. 相似文献
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V. A. Shefer 《Solar System Research》2010,44(2):152-165
We propose a new method for the determination of the preliminary orbit of a small celestial body using three pairs of its
angular coordinates in three moments of time. The method is based on the use of the intermediate orbit we constructed earlier
using three position vectors and the corresponding time moments. This intermediate orbit accounts for the main part of the
perturbations of the motion of the body under study. We compare the results obtained by the classical Lagrange-Gauss method,
Herrick-Gibbs method, generalized Herrick-Gibbs method, and the new method by the examples of the determination of the orbit
of the small planet 1566 Icarus. The comparison showed that the new method is a highly efficient tool for the study of perturbed
motion. It is especially efficient when applied to high-precision observational data covering short arcs of the orbit. 相似文献
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The preliminary orbit determination with optical angular measure- ments plays an important role in the survey of space objects. The classical method of orbit computation based on the least square error estimation is not robust while outliers occur in the observation. A robust method is proposed by employing the least absolute deviation estimation. The method reduces the problem of orbit determination to a linear programming problem, and gives the variance of the estimation with the bootstrap method. Numerical check shows that the method is effective and robust, and has a high breakdown point. 相似文献
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It is difficult to use the single-station satellite laser ranging (SLR) data for orbit determination, due to the singular geometrical distribution of the observations. The single-station data produced by performing the diffuse- reflection SLR on the earth-orbiting space debris are therefore ineffective for orbit improvement. To solve this problem, we propose an orbit determination method by using single-station SLR data in aid of the two-line element set (TLE). For verifying its feasibility, this method is implemented and applied to the orbit determination of the satellite Ajisai, using the single-station SLR data of five passes in one day and the corresponding TLE. And on this basis, the five-day orbit prediction is generated, the result indicates that the errors of predicted positions are less than 40 m. In addition, the potential application of this method in the orbit improvement of space debris is discussed. 相似文献
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C. R. Traas 《Celestial Mechanics and Dynamical Astronomy》1985,36(4):299-317
The applicability of advanced numerical methods for the solution of the orbit determination problem is studied.The dynamics of the observed object is written as a system of integral equations. This system is solved numerically by representing the components of the force function as linear combinations of B-splines and by applying the multigrid technique. In an outer loop the orbit determination problem is solved using Newton's method.The method is suitable for both preliminary orbit determination and orbit improvement.Most of the programming and part of the analysis was done by G. Zwier, in partial fulfilment of the requirements for obtaining the degree of master in applied mathematics at the Twente University of Technology. 相似文献
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Roberto Armellin Pierluigi Di Lizia Michele Lavagna 《Celestial Mechanics and Dynamical Astronomy》2012,112(3):331-352
A method for high-order treatment of uncertainties in preliminary orbit determination is presented. The observations consist
in three couples of topocentric right ascensions and declinations at three observation epochs. The goal of preliminary orbit
determination is to compute a trajectory that fits with the observations in two-body dynamics. The uncertainties of the observations
are usually mapped to the phase space only when additional observations are available and a least squares fitting problem
is set up. A method based on Taylor differential algebra for the analytical treatment of observation uncertainties is implemented.
Taylor differential algebra allows for the efficient computation of the arbitrary order Taylor expansion of a sufficiently
continuous multivariate function. This enables the mapping of the uncertainties from the observation space to the phase space
as high-order multivariate Taylor polynomials. These maps can then be propagated forward in time to predict the observable
set at successive epochs. This method can be suitably used to recover newly discovered objects when a scarce number of measurements
is available. Simulated topocentric observations of asteroids on realistic orbits are used to assess the performances of the
method. 相似文献
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SONG Ye-zhi HUANG Yong HU Xiao-gong LI Pei-jia CAO Jian-feng 《Chinese Astronomy and Astrophysics》2014
It is known that the dynamical orbit determination is the most common way to get the precise orbits of spacecraft. However, it is hard to build up the precise dynamical model of spacecraft sometimes. In order to solve this problem, the technique of the orbit determination with the B-spline approximation method based on the theory of function approximation is presented in this article. In order to verify the effectiveness of this method, simulative orbit determinations in the cases of LEO (Low Earth Orbit), MEO (Medium Earth Orbit), and HEO (Highly Eccentric Orbit) satellites are performed, and it is shown that this method has a reliable accuracy and stable solution. The approach can be performed in both the conventional celestial coordinate system and the conventional terrestrial coordinate system. The spacecraft's position and velocity can be calculated directly with the B-spline approximation method, it needs not to integrate the dynamical equations, nor to calculate the state transfer matrix, thus the burden of calculations in the orbit determination is reduced substantially relative to the dynamical orbit determination method. The technique not only has a certain theoretical significance, but also can serve as a conventional algorithm in the spacecraft orbit determination. 相似文献