利用地球定向参数确定依巴谷输入星表与射电天球参考架之间的旋转

通过比较地球定向参数（ＥＯＰ）序列和对应的地固参考架，本文得到了依巴谷输入星表（ＨＩＣ）和国际地球自转服务（ＩＥＲＳ）基于甚长基线干涉测量（ＶＬＢＩ）建立的河外天球参考架（ＩＣＲＦ）之间的旋转参数，在Ｊ２０００．０历元，前者至后者的旋转参数为［８．４±１．１ｍａｓ，４６．７±１．１ｍａｓ，４５．５±１．５ｍａｓ］，其时间变率为［－０．１４±０．０５ｍａｓ／ａ，３．２２±０．０５ｍａｓ／ａ，５．７０±０．０７ｍａｓ／ａ］。依巴谷输入星表是完全基于ＦＫ５系统的，本文得到的旋转参数与ＩＣＲＦ和ＦＫ５之间的系统差异情况相符     

空间VLBI研究的现状和未来

空间ＶＬＢＩ卫星ＶＳＯＰ／ＨＡＬＣＡ是日本宇航科学研究所（ＩＳＡＳ）的飞行任务,已经在１９９７年２月升空。它拥有８ｍ直径的射电望远镜,远地点达２２０００ｋｍ。和地面的射电望远镜联合观测（干涉观测）,其最高分辨率比地面ＶＬＢＩ提高了３倍。该项空间ＶＬＢＩ观测由ＮＳＡＳ的地面跟踪站支持。第一批ＶＬＢＩ图像已经在因特网上发表。ＲａｄｉｏＡｓｔｒｏｎ项目由俄罗斯科学院列别捷夫物理研究所天文空间中心（ＡＳＣ     

视超光速源0106 013的观测研究

我们在利用上海和ＳＨＥＶＥ组成的ＶＬＢＩ网做南天区５ＧＨｚＶＬＢＩ普查的过程中，对致密射电源０１０６＋０１３的视超光速运动作了进一步的研究．结果表明：（１）分量１最有可能是核；（２）原视超光速喷流分量仍以０．２ｍａｓ／ｙｒ的自行速度向外运动；（３）发现一个新分量的爆发，新分量也是视超光速的，自行速度为０．１８ｍａｓ／ｙｒ；（４）喷流在大约５ｍａｓ处有较明显的弯曲，然后趋于与ＶＬＡ喷流的方向一致．     

IGS′92联测期间地极坐标的高频波动

本文分析了ＩＧＳ＇９２联测期间七个ＧＰＳ数据处理中心提供的极坐标序列。通过谱分析、最小二乘拟合和Ｆ检验，表明在这些序列中存在一些共同的高频波动：在Ｘ方向上具有２７．０，１６．５，１３．４和１０．４天的周期，在Ｙ方向上的波动周期约为２０．５，１５．８和１０．０天。并且每个序列与ＥＯＰ（ＩＥＲＳ）９２Ｃ０４之间都存在一个系统差。计算与分析表明，这些系统偏离的主要原因是由于在用ＧＰＳ资料解算Ｘ、Ｙ时，不同分析中心采用了不同系统的台站坐标（或者说只有部分台站采用了固定的台站坐标），从而造成这些序列所在的参考架与ＩＴＲＦ９１之间存在一个平移和旋转。最后，计算了该期间的大气角动量激发函数，可部分地解释该期间的Ｘ、Ｙ高频波动的原因。     

VLBI天体物理学的发展（续）

ＶＬＢＩ天体物理学的发展（续）万同山（接上期）下一代的ＶＬＢＩ以ＶＬＢＡ和Ｒａｄｉｏａｓｔｒｏｎ空间ＶＬＢＩ站为代表。美国国立射电天文台的ＶＬＢＡ是世界上第一个ＶＬＢＩ专用设备，在美国领土上从夏威夷到维尔京群岛上放置了１０个２５米口径的射电望远镜，最...     

日长年际变化的主要激发源

将年际时间尺度上的△ＬＯＤ序列（１９５８．０－１９９８．０）与大气角动量变化（纬向风）风的激发和ＳＯＩ等作比较,表明大气动力学过程是年际时间尺度△ＬＯＤ变化的重要激发源,在实测△ＬＯＤ、纬向风激发和ＳＯＩ中存在的一些相近的频率分量,但是,在实测△ＬＯＤ中有若干很强的信号（如平均周期约６．３年,平均振幅约０．１３ｍｓ的主要分量,以及平均周期约９．０年,平均振幅约０．０７ｍｓ的分量）在纬向风激发和ＳＯ     

VLBI天体物理学的发展（续）

ＶＬＢＩ天体物理学的发展（续）万同山（接上期）从目前地面ＶＬ－ＢＩ阵的情况看来，毫米波ＶＬＢＩ的发展还有相当的困难。一个主要困难是毫米波射电望远镜太少，而且口径太小，再者一个射电望远镜要装备成ＶＬＢＩ单元，所需的氢原子钟和ＶＬＢＩ专用终端设备也是很大...     

VLBI天体物理学的发展

ＶＬＢＩ天体物理学的发展万同山ＶＬＢ互（ＶｅｒｙＬ。匡ｋ。ｕｎｅｈ比ｒｋｒ。ｍ幻ｒｙ，甚长基线干涉测量法）天体物理学成为射电天文学的一个分支是大约近２０年的事。ＶＬＢＩ天文学研究从实验到形成科学经历了一个发展的过程。第一个ＶＬＢＩ实验是１９６７年在美...     

南天区耀变体的VLBI研究

本文报道南天区５ＧＨｚＶＬＢＩ的第二轮观测．第二轮观测是在１９９３年５月期间进行的，共观测了２５个射电源，检测到２４个源，获得了２３个南天区耀变体（Ｂｌａｚａｒ）的ＶＬＢＩ高分辨率的图象，其中１５个是第一次ＶＬＢＩ成图，７个是高能（＞１００ＭｅＶ）γ射电源，１２个源呈现核－喷流结构，其余１１个源是单一的致密核，未发现致密双源．有两个源可能有视超光速现象．     

天测与测地VLBI资料处理中的剩余钟行为建模

利用实测资料和模拟数据，分析了在天测与测地VLBI数据处理软件CALC／SOLVE中，剩余钟行为连续分段线性拟合的局限性和周期函数拟合的可行性．对CALC／SOLVE系统增配了周期函数拟合模块，并选取了1990年至2001年的1567次天测与测地VLBI实验，进行了剩余钟行为两种拟合模型情况下的实测资料综合解算．结果表明，在获得同等水平的时延拟合残差加权均方根(wrms)的情况下，对剩余钟行为采用周期函数拟合，使得解算参数的个数相比于连续分段线性拟合有显著减少，提高了解算的自由度．虽然在两种模型情况下的台站和射电源坐标以及地球定向参数等的解算精度无显著差异，但周期函数拟合存在可以识别的优势，85％以上的台站坐标和74％以上的源坐标以及51％以上的EOP精度均有所提高，均值分别为0．02mm、0．3μas和1．5μas．     

Toward the construction of a new precession-nutation theory of nonrigid Earth

The accuracy of the rigid Earth solution SMART97 is 2?μ as over the time interval (1968, 2023), accuracy showed by the comparison with a numerical integration using the positions of the Moon, the Sun, and the planets given by DE403. To obtain a nonrigid Earth solution, we use the transfer function of Mathews et al. (2000) and , to keep the precision of our rigid Earth solution in the computation of the geophysical effects, we apply this transfer function to the Earth's angular velocity vector in order to avoid the inherent approximations of the classical methods. Moreover the perturbations of the third component of the angular velocity vector are taken into account. Lastly, we take into account, in an iterative process, the second order perturbations due to the geophysical effects. The results are compared with the Herring solution (1996) published in the IERS Conventions.     

Coordinate Additional Perturbations to Mars Orbiters and Choice of Corresponding Coordinate System

Similar to the study of the related problems of Earth satellites, in the research of the motion of Mars orbiter especially for low-orbit satellites, it is more appropriate to choose an epoch Mars-centered and Mars-equator reference system, which indeed is called the Mars-centered celestial coordinate system. In this system, the xy-plane and the direction of the x-axis correspond to the mean equator and mean equinox. Similar to the precession and nutation of the Earth, the wiggling of instantaneous Mars equator causes the coordinate additional perturbations in this Mars coordinate system. The paper quotes a method which is similar to the one used in dealing with the coordinate additional perturbations of Earth. According to this method, based on the IAU2000 Mars orientation model and under the precondition of a certain accuracy, we are able to figure out the precession part of the change of Mars gravitation. This lays the foundation for further study of its influence on the Mars orbiter's orbit of precession and the solution of the corresponding coordinate additional perturbations. The obtained analytical solution is easy to use. Compared with the numerical solution with higher accuracy, the result shows that the accuracy of this analytical solution could satisfy the general requirements in use. Therefore, our result verifies that a unified coordinate system, the Mars-centered celestial system in which J2000.0 is chosen as its current initial epoch, could be applied to deal with the relative problems of Mars orbiters, especially for low-orbit satellites. It is different from the method we previously used in dealing with the corresponding problems of Earth satellites, where we adopted the instantaneous equator and epoch (J1950.0) mean equinox as xy-plane and the direction of x -axis. In contrast, the coordinate transformation brings heavy workload and certain inconvenience in relative former works in which the prior system is used. If adopting the unified coordinate system, the transformation could be simply avoided and the computation load could be decreased significantly.     

预报大行星,月球掩点源事件的一种方法

以ＪＰＬ提供的太阳系天体数值历表ＤＥ２００／ＬＥ２００和美国海军天文台提供的岁差、章动改正程序为出发点，本文介绍预报大行星、月球掩源的一种方法，本方法分三个步骤：首先给出被掩源所满足的必要条件，并据此进行被掩源的初选；其次预报掩事件的全局情况，即掩发生的始终时刻和比较精确的地球椭球表面上可观测区域边界，在可观测区域边界中，本文发现了文献中未见出现过的出没南北界最后；预报地方见掩情况。     

Solution to the rotation of the elastic earth by method of rigid dynamics

Hamiltonian mechanics is applied to the problem of the rotation of the elastic Earth. We first show the process for the formulation of the Hamiltonian for rotation of a deformable body and the derivation of the equations of motion from it. Then, based on a simple model of deformation, the solution is given for the period of Euler motion, UT1 and the nutation of the elastic Earth. In particular it is shown that the elasticity of the Earth acts on the nutation so as to decrease the Oppolzer terms of the nutation of the rigid Earth by about 30 per cent. The solution is in good agreement with results which have been obtained by other, different approaches.     

The evolution of the lunar orbit revisited. I

After recalling the contribution of Halley, J. Kepler, and G. Darwin to our understanding of the secular acceleration of the Moon, we establish a set of differential equations for the variation of the semi-major axis, and the inclination of the Moon on the maximum area plane. These equations are obtained without expanding the disturbing function, due to the tidal bulge, in term of the elliptic elements. The equations thus obtained are simple enough to allow us a qualitative discussion of the solution, followed by a numerical integration.The results obtained show the Moon was in the distant past in a retrograde orbit, approaching the Earth, its inclination increasing towards 90°; once after a closer approach to the Earth, the Moon receeded and it will finally reach an equilibrium point, the orbital and the equatorial planes being blended.The solution of the equations appears as a fascicle of curves, becoming extremely dense as we come nearer to the present. Owing to the high sensitivity of the solution to the initial conditions, a weak disturbance added to our modeled forces may lead to a past situation very different from the conclusion drawn by Goldreich (1966) and MacDonald (1964); the minimal approach distance could be greater than 10 Earth's radii.     

Analytical expressions of the Earth's position and velocity for the calculation of apparent positions

In order to calculate the apparent places of stars, the barycentric and heliocentric positions of the Earth and the barycentric velocity of the Earth are required. It is shown that several tens of trigonometric terms for their expressions are sufficient for analyses of optical observations which have an observational accuracy of the order of 0.001. We also give the analytical expressions of the position and velocity of the Earth with higher precision so that we can use them in the analyses of precise astrometry such as VLBI observations.     

Single-point position estimation in interplanetary trajectories using star trackers

This study provides a single-point position estimation technique for interplanetary missions by observing visible planets using star trackers. Closed-form least-squares solution is obtained by minimizing the sum of the expected object-space squared distance errors. A weighted least-squares solution is provided by an iterative procedure. The weights are evaluated using the distances to the planets estimated by the least-squares solution. It is shown that the weighted approach only requires one iteration to converge and results in significant accuracy gains compared to simple least squares approach. The light-time correction is taken into account while the star-light aberration cannot be implemented in single-point estimation as it requires knowledge of the observer velocity. The proposed method is numerically validated through a statistical scenario as follows. A three-dimensional grid of test cases is generated: two dimensions sweep through the ecliptic plane and the third dimension sweeps through time from January 1, 2018 to January 1, 2043 in 5-year increments. The observer position is estimated at each test case and the estimate error is recorded. The results obtained show that a large majority of positions are well suited to position estimation by using star trackers pointing to visible planets, and reliable and accurate single-point position estimations can be provided in interplanetary missions. The proposed approach is suitable to be used to initiate a filtering technique to increase the estimation accuracy.     

A solution of linearized Einstein field equations in vacuum used for the detection of the stochastic background of gravitational waves

A solution of linearized Einstein field equations in vacuum is given and discussed. First it is shown that, computing from our particular metric the linearized connections, the linearized Riemann tensor and the linearized Ricci tensor, the linearized Ricci tensor results equal to zero. Then the effect on test masses of our solution, which is a gravitational wave, is discussed. In our solution test masses have an apparent motion in the direction of propagation of the wave, while in the transverse direction they appear at rest. In this way it is possible to think that gravitational waves would be longitudinal waves, but, from careful investigation of this solution, it is shown that the tidal forces associated with gravitational waves act along the directions orthogonal to the direction of propagation of waves. The computation is first made in the long wavelengths approximation (wavelength much larger than the linear distances between test masses), then the analysis is generalized to all gravitational waves.

In the last sections of this paper it is shown that the frequency dependent angular pattern of interferometers can be obtained from our solution and the total signal seen from an interferometer for the stochastic background of gravitational waves is computed.     

The transmission of mass and angular momentum from a satellite or planetary system to its primary

In this paper main implication of basic properties detected in the satellite systems of Jupiter, Saturn and Uranus, and presented by the author in an earlier contribution (Barricelli, 1971b) are investigated. The similarity between the primary periods in the three systems, their apparent relation to the axial rotation periods of the three planets and other features suggesting that collisions with the planetary surfaces may have played a role in the evolution of the three satellite systems are interpreted by assuming that in each case a satellite of unusually large size was originally disintegrated at the Roche limit of its primary. The disintegration of large satellites and their fusion with the respective planets is assumed to be a normal feature in the latest stage of planetary growth and the main cause of axial rotation in the respective planets.These assumptions make it possible to give a selfconsistent interpretation of the similarity between the axial rotation periods of the three planets and their relation to the primary periods (as defined by Barricelli, 1971b) in the three systems.Similar assumptions when applied to the Earth-Moon system make it possible to understand why the Moon, in its closest approach to the Earth is found to have been almost exactly at the Roche limit (Gerstenkorn, 1955; MacDonald, 1964), a coincidence which is too good to be accidental. According to this interpretation our Moon is a portion (representing about one third) of our original satellite, which survived its approach to the Roche limit and the ensuing fusion process with the Earth. It can be shown (see text) that under certain conditions this could leave a residual satellite with a stationary distance from the Earth (which in retrospect would be identified as its lowest distance from the Earth) at the Roche limit.The only other case in which we have observational evidence of parts of a satellite surviving its fusion process at the Roche limit is represented by the rings of Saturn and possibly the small innermost satellite Janus which seems to have been feeding on the rings.     

The INPOP10a planetary ephemeris and its applications in fundamental physics

Compared to the previous INPOP versions, the INPOP10a planetary and lunar ephemeris has several improvements. For the planets of our Solar System, no big change was brought in the dynamics but improvements were implemented in the fitting process, the data sets used in the fit and in the selection of fitted parameters. We report here the main characteristics of the planetary part of INPOP10a like the fit of the product of the solar mass with the gravitational constant ( GM_\odot{{\rm GM}_{\odot}}) instead of the astronomical unit. Determinations of PPN parameters as well as adjustments of the Sun J2 and of asteroid masses are also presented. New advances of nodes and perihelia of planets were also estimated and are given here. As for INPOP08, INPOP10a provides to the user, positions and velocities of the planets, the Moon, the rotation angles of the Earth and the Moon as well as TT-TDB Chebyshev polynomials at .