共查询到20条相似文献，搜索用时 31 毫秒
1.
Sh. Sh. Dolginov Ye. G. Yeroshenko V. A. Sharova T. A. Vnuchkova L. L. Vanyan B. A. Okulessky A. T. Bazilevsky 《Earth, Moon, and Planets》1976,15(1-2):3-14
The data of three-times repeated magnetic survey of the section of Lunokhod-2 route 1.5 km long are analyzed. The linear size of the regions of magnetic field anomalies disclosed is 200–300 m. The results of magnetic survey near the tectonic break of Straight Rille and near the south rim of crater Le Monnier were used for estimation of rock magnetization in situ. It is shown that mare basalts in south-east region of crater Le Monnier have oblique magnetization (at the angle ç30° to horizon). The magnitude of magnetization is × 5 × 10–5 G cm g–1. The south-east slope of the crater Le Monnier is magnetized roughly vertically, the upper limit of magnetization of the rocks of the rim is ç 1 × 10–5 G cm3 g–1. The results of an analysis of 160 magnetic field variations recorded by Lunokhod-2 indicate that the horizontal components of variations have nearly linear polarization. The principal axes of hodographs stretch in the direction north-west-south-east. Such a polarization of variations may be due to an increase of the thickness of the upper isolated layer under Mare Serenitatis. 相似文献
2.
《Meteoritics & planetary science》1993,28(4):603-604
Book Revieweds in this article: The Shadows of Creation by Michael Riordon and David Schramm. W.H. Freeman From Stone to Star by Claude Allègre GPS Satellite Surveying by Alfred Leick Le Fer de Dieu by Théodore Monod and Brigitte Zanda Meteoritter, nøglen til Jordens Fortid by Vagn F. Buchwald 相似文献
3.
Equivalent width calculations for some electronic and vibration-rotation transitions of the molecules PO, PH, MgH+f, and CN have been carried out for a few umbral, photospheric, and facular model atmospheres. It appears that a few weak lines of these molecules might show up in the umbral spectrum. Le Blanc bands of CN are too weak for detection in the solar spectrum. 相似文献
4.
卫星双向时间比对及其误差分析 总被引：26，自引：0，他引：26
介绍了卫星双向时间比对(TwsTT)方法的发展过程及其基本原理，讨论了TwsTT的误差源，分析了各误差源对比对精度的影响。得出影响TwSTT精度的主要误差源为设备时延误差和路径传播时延误差，而由于卫星和地面站运动引起的误差相对较小，从而给出了实际应用时不同比对精度下需要考虑的误差源及对误差源的精度要求。 相似文献
5.
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. 相似文献
6.
在自适应光学系统中，波前探测器的噪声、未完全补偿湍流所引起的误差以及变形镜的拟合误差是主要的误差源．本文针对已经建立的2．16m望远镜红外自适应光学系统，从伺服控制系统的角度分析了该系统的闭环噪声、大气湍流引起的误差以及该系统的闭环总体误差．该系统的闭环总体误差是光强及系统闭环带宽的函数．本文还分析了该系统的有效性以及对大气湍流不同改善程度情况下光强与闭环带宽的关系．并在此基础上给出了该系统的最佳带宽选取及系统的极限工作星等． 相似文献
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8.
本文根据误差理论,对ＰＵＶＭ２测轨方法的误差及其传播规律进行了初步的分析和研究,给出了卫星的轨道根数σ和空间位置ｒ↑→的内符合误差估计公式。 相似文献
9.
A. G. Kosovichev 《Solar physics》2006,237(1):1-11
The purpose of this article is to carry out a power-spectrum analysis of the Super-Kamiokande five-day dataset that takes
account of the asymmetry in the error estimates. Whereas for symmetrical error estimates the likelihood analysis involves
a linear optimization procedure, for asymmetrical error estimates it involves a nonlinear optimization procedure. For most
frequencies there is little difference between the power spectra derived from analyses of symmetrized error estimates and
from asymmetrical error estimates, but this is not the case for the principal peak in the power spectrum at 9.43 yr −1. A likelihood analysis that takes account of the error asymmetry leads to a peak with power 13.24 at that frequency, and
a Monte Carlo analysis shows that there is a chance of only 0.1% of finding a peak this big or bigger in the search band 1
– 36 yr −1. From this perspective, power-spectrum analysis that takes account of asymmetry of the error estimates gives evidence for
variability that is significant at the 99.9% level. We comment briefly on an apparent discrepancy between power-spectrum analyses
of the Super-Kamiokande and SNO solar neutrino experiments. 相似文献
10.
11.
The ecliptic as a mean orbital plane of the Sun in Le Verrier's theory is a mean orbital plane determined from the secular parts of the longitude of the ascending node and the inclination of the Sun with respect to a reference plane. On the other hand, the ecliptic in Newcomb's theory is so chosen that the latitude with respect to his ecliptic does not have cosg nor sing whereg is the mean anomaly of the Sun. The two definitions are really different in spite of their apparent similarity. Standish (1981) defined the ecliptic from a kinematical point of view, and it is shown that the ecliptic defined by Standish (in the rotating sense) does coincide with the ecliptic defined by Newcomb. 相似文献
12.
We systematically investigate stellar encounters in their six‐dimensional phase space, including also the error ellipsoid and its evolution in time. It allows to give not only a mathematical model of stellar encounters but also an error model for this process. On that occasion we derive fundamental formulae for the positional error in ℝn: the probability of a position X falling into the error ellipsoid, the standard deviation in an arbitrary direction, and we briefly discuss the mean positional error in ℝn. The case of the close encounter of the star GL 710 (HIP 89825) is an illuminating example of applying the derived results. Moreover, we show that the error ellipsoid can also be successfully applied to approximate the confidence region (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
13.
L. L. Vanyan T. A. Vnuchkova I. V. Egorov A. T. Basilevsky E. G. Eroshenko E. B. Fainberg P. Dyal W. D. Daily 《Earth, Moon, and Planets》1979,21(2):185-192
Magnetic fluctuations measured by the Lunokhod 2 magnetometer in the Bay Le Monnier are distinctly anisotropic when compared to simultaneous Apollo 16 magnetometer data measured 1100 km away in the Descartes highlands. This anisotropy can be explained by an anomalous electrical conductivity of the upper mantle beneath Mare Serenitatis. A model is presented of anomalously lower electrical conductivity beneath Serenitatis and the simultaneous magnetic data from the Lunokhod 2 site at the mare edge and the Apollo 16 site are compared to the numerically calculated model solutions. This comparison indicates that the anisotropic fluctuations can be modeled by a nonconducting layer in the lunar lithosphere which is 150 km thick beneath the highlands and 300 km thick beneath Mare Serenitatis. A decreased electrical conductivity in the upper mantle beneath the mare may be due to a lower temperature resulting from heat carried out the magma source regions to the surface during mare flooding. 相似文献
14.
Georges Balmino 《Celestial Mechanics and Dynamical Astronomy》1994,60(3):331-364
The spherical harmonic coefficients of the gravitational potential of an homogeneous body are analytically derived from the harmonics describing its shape. General formulas are given as well as detailed expressions up to the fifth order of the topography harmonics. The volume, surface and inertia tensor of the body are obtained as by-products. The case of a triaxial ellipsoid is given as example and used for numerical checking. Another numerical scheme for verification is provided. The application to Phobos is made and the convergence of the expressions for the harmonics is numerically established.
Résumé Les harmoniques du champ de gravitation d'un corps homogène de forme donnée sont calculés analytiquement à partir des harmoniques du développement en série du rayon vecteur exprimant la forme de la surface du corps. Outre la formule générale, des expressions détaillées, au cinquième ordre des harmoniques du rayon vecteur, sont données sous une forme bien adaptée à la programmation. Le volume, la surface et le tenseur d'inertie du corps sont calculés analytiquement `a partir des formules générales. Le cas de l'ellipsoide triaxial est pris comme test des formules établies. Un autre test numérique est fourni dans le cas le plus général. Ceci est appliqué à Phobos, et la convergence des expressions fournissant les harmoniques est numériquement démontrée.相似文献
15.
《New Astronomy》2003,8(7):665-677
We present a detailed analysis of the error budget for the TreePM method for doing cosmological N-body simulations. It is shown that the choice of filter for splitting the inverse square force into short and long range components suggested in Bagla [Bagla, J.S., 2002a. JApA 23, 185; Bagla, J.S., 2002b. Preprint. To appear in Proceedings of the Numerical Simulations in Astrophysics, Tokyo, July 2002] is close to optimum. We show that the error in the long range component of the force contributes very little to the total error in force. Errors introduced by the tree approximation for the short range force are different from those for the inverse square force, and these errors dominate the total error in force. We calculate the distribution function for error in force for clustered and unclustered particle distributions. This gives an idea of the error in realistic situations for different choices of parameters of the TreePM algorithm. We test the code by simulating a few power law models and checking for scale invariance. 相似文献
16.
An Improved Grey Model and Its Application Research on the Prediction of Real-time GPS Satellite Clock Errors 总被引：2，自引：0，他引：2
In the work on the real-time GPS precise point positioning, the realtime and reliable prediction of the satellite clock error is one of the keys to the realization of the GPS real-time high accuracy point positioning. The satelliteborne GPS atomic clock has high frequency, is very sensitive and extremely easy to be influenced by the outside world and its own factors. Therefore, it is very difficult for one to know well its complicated and detailed law of change, with these attributes being in accordance with the characteristics of the theory of grey system. Thus, it is considered that the process of variation of the clock error is regarded as a grey system. On the basis of the exploration of the limitations of the quadratic polynomial and grey model satellite clock error predictions, the research on the real-time prediction of the GPS satellite clock error by taking advantage of the improved grey model is proposed. Finally, the materials of the GPS satellite clock error of 3 different time intervals are used to make the accuracy analysis of the clock error prediction of different sampling intervals, to study the relation between the grey model exponential coefficient and the prediction accuracy and to make the analysis of the comparison of the prediction accuracy with that of the quadratic polynomial method. The general relation between the different types of satellite clock errors and the model exponential coefficients is summarized and compared with the IGS final clock error ephemeris product to test and verify the feasibility and availability of the improved prediction model proposed in the present article so as to provide the higher-accuracy satellite clock error products for the real-time GPS dynamic precise point positioning. 相似文献
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18.
In the automated(computerized) meridian circle, the graduation error can be calibrated in a short time: a complete determination of the graduation error takes a few days, while a coarse measurement of the first ten dominant Fourier components of the graduation error takes only 15 min. Thus, we can monitor the annual and diurnal variations of the graduation. In our regular observations, the annual variation can be thus corrected for. This kind of correction seems to be necessary, judging from the observing accuracy of modern meridian observations. On the other hand, we could not detect a change of the graduation within one clear day as far as the dominant components of the diameter error are concerned. In our case we can therefore assume the graduation error to be constant within one day. 相似文献
19.
《Astroparticle Physics》2007,26(6):375-379
The development of an ultra high energy air shower has an intrinsic energy fluctuation due both to the first interaction point and to the cascade development. Here we show that for a given primary energy this fluctuation has a lognormal distribution and thus observations will estimate the primary energy with a lognormal error distribution. We analyze the UHECR energy spectrum convolved with the lognormal energy error and demonstrate that the shape of the error distribution will interfere significantly with the ability to observe features in the spectrum. If the standard deviation of the lognormal error distribution is equal or larger than 0.25, both the shape and the normalization of the measured energy spectra will be modified significantly. As a consequence, the GZK cutoff might be sufficiently smeared as not to be seen (without very high statistics). This result is independent of the power law of the cosmological flux. As a conclusion we show that in order to establish the presence or not of the GZK feature, not only more data are needed but also that the shape of the energy error distribution has to be known well. The high energy tail and the sigma of the approximate lognormal distribution of the error in estimating the energy must be at the minimum set by the physics of showers. 相似文献
20.
The development of an ultra high energy air shower has an intrinsic energy fluctuation due both to the first interaction point and to the cascade development. Here we show that for a given primary energy this fluctuation has a lognormal distribution and thus observations will estimate the primary energy with a lognormal error distribution. We analyze the UHECR energy spectrum convolved with the lognormal energy error and demonstrate that the shape of the error distribution will interfere significantly with the ability to observe features in the spectrum. If the standard deviation of the lognormal error distribution is equal or larger than 0.25, both the shape and the normalization of the measured energy spectra will be modified significantly. As a consequence, the GZK cutoff might be sufficiently smeared as not to be seen (without very high statistics). This result is independent of the power law of the cosmological flux. As a conclusion we show that in order to establish the presence or not of the GZK feature, not only more data are needed but also that the shape of the energy error distribution has to be known well. The high energy tail and the sigma of the approximate lognormal distribution of the error in estimating the energy must be at the minimum set by the physics of showers. 相似文献