天王星卫星的星历表计算

根据天王星卫星的运动理论模型（GUST86），建立了一套5颗主要卫星的星历表计算和误差分析程序。对部分高精度卫星观测位置资料进行的O－C计算和分析表明了计算程序的正确性和实用性。     

天王星卫星位置可视化软件设计

为了满足大行星卫星的高精度CCD位置观测与运动理论研究工作的需要 ,采用天王星 5颗主要卫星摄动理论模型 (Gust86 )作为核心 ,设计了一个天王星视位置可视化软件。该软件具有卫星证认 ,最佳观测时段选取 ,精确模拟卫星视运动和实时引导CCD精密定位观测等功能。     

天王星卫星的星历表计算

根据天王星卫星的运动理论模型，建立了一套５颗主要卫星的星历表计算和误差分析程序。对部分高精度卫星观测位置资料进行的Ｏ－Ｃ计算和分析表明了计算程序的正确性和实用性。     

高精度测定外行星位置-可行性及实验

大行星位置的测量是天体测量学中的一项长期而重要的任务。如何在当前形势下高精度测定行星的位置是本文研究方向的最终目标。鉴于太阳系内行星和木星都有新技术进行高精度的位置观测,作者探讨了如何用光学手段高精度测定外行星（土星,天王星和海王星）的位置,提出了用长焦距望远镜ＣＣＤ观测行星卫星和用中天望远镜ＣＣＤ观测暗恒星相配合的思路。因此,对长焦距望远镜ＣＣＤ观测外行星卫星和中天望远镜ＣＣＤ相对观测恒星进行了系统调研,同时也对外行星卫星的理论从观测验证的角度进行了介绍。本文重点介绍了在长焦距望远镜上相对于天王星卫星高精度测定暗恒星的位置。结果表明,相对于天王星卫星确实可以精确测定同一ＣＣＤ视场中暗恒星的位置,位置测量的精度和国外最好的天王星卫星位置测量的精度相当或更高。还介绍了与观测资料的归算有关的天王星和卫星的位置历算。最后,分析了我国从事高精度大行星位置测量的可行性     

天王星卫星的CCD观测与分析解的比对

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。     

天王星与依巴谷恒星的合

根据最新星历表，天王星及其卫星系统将于2001年9月6日-11日期间经过2颗较亮的恒星，它们分别是依巴谷恒星（星号106829）和ACT星表恒星（AC2000星号2588165），其中天王星与依巴谷恒星的最小角距离为5.90″，5颗主要卫星（irands,Ariel,Umbriel,Titania和Oberon)中与依巴谷恒星最小角距离的是Titania，角距离仅为2.08″，届时，这种非常近的合天象的长焦距望远镜的CCD观测将具有重要意义。     

天王星与依巴谷恒星的合

根据最新星历表，天王星及其卫星系统将于2001年9月6日～11日期间经过2颗较亮的恒星。它们分别是依巴谷恒星(星号106829)和ACT星表恒星(AC2000星号2588165)。其中天王星与依巴谷恒星的最小角距离为5.90″,5颗主要卫星(Mirands,Ariel,Umbriel,Titania和Oberon)中与依巴谷恒星最小角距离的是Titania,角距离仅为2.08″。届时，这种非常近的合天象的长焦距望远镜的CCD观测将具有重要意义。     

天王星卫星CCD观测的初步分析

１９９５ 年８ 月在上海天文台利用安装在１ ．５６ 米望远镜上的ＣＣＤ 探测器对天王星五颗主要卫星进行了定位试观测。将观测所得的位置资料与其理论值做了比较。结果表明：ＣＣＤ观测的位置精度优于照相观测的结果。这些资料对于卫星轨道的研究是有价值的。     

天王星卫星的位置测定及与理论值的比较

本文发表的是我们于１９９０年在云南天文台利用１ｍＲＣＣ望远镜对天王星主要卫星进行照像观测的定位结果以及与理论计算值进行的比较分析。     

天文巨星——冰界

230年前的1781年,业余天文学家赫歇尔在望远镜里发现了天王星;25年前的1986年。“旅行者2号”（Voyager 2）行星探测器在飞往外太阳系的途中,对天王星进行了人类首次也是目前为止惟一一次“近距”观测。     

Astrometric observations of the Uranian satellites with the Faulkes Telescope North in 2007 September

The results of astrometric observations of the main Uranian satellites taken with the Faulkes Telescope North are presented. A median filter algorithm was applied to subtract a scattered-light halo caused by Uranus. The Two-Micron All-Sky Survey (2MASS) and USNO-B1.0 were used as reference catalogues. The mean value of the differences between the equatorial coordinates of the satellites determined with 2MASS and USNO-B1.0 is close to 200 mas. A comparison of the observed equatorial coordinates of the satellites and their relative positions with ephemerides based on different combinations of theories of motion of Uranus and its satellites (DE405+GUST86, DE405+GUST06, INPOP+GUST86, INPOP+GUST06) was performed. The satellites' positions obtained with respect to 2MASS are in better agreement with theories. The values of (O−C) of the equatorial coordinates determined with the 2MASS are mainly less than 100 mas. The majority of (O−C) of relative positions are within ±50 mas. The mean values of the standard errors of (O−C) are within 20 to 60 mas.     

A new dynamical model for the Uranian satellites

We have developed a new dynamical model of the main Uranian satellites, based on numerical integration and fitted to astrometric observations. Old observations, as well as modern and Voyager observations have been included. This model has provided ephemerides that have already been used for predicting the mutual events during the PHE-URA campaign. It is updated here to improve the prediction of these events. We also tried to assess the real accuracy of our ephemerides by checking the distance differences of the Uranian satellites, using simultaneously our former and new model. It appears that both solutions are very close to each other (within few tens of kilometers), and most probably accurate at the level of few hundred of kilometers. Using new available meridian observations of the Uranian satellites, we have checked the Uranian ephemeris accuracy using DE406. An error of more than 0.1 arcsec on the Uranian position is observed.     

Nonlinear theory of secular perturbations of satellites of an oblate planet

Anonlinear analytical theory of secular perturbations in the problem of the motion of a systemof small bodies around a major attractive center has been developed. Themutual perturbations of the satellites and the influence of the oblateness of the central body are taken into account in the model. In contrast to the classical Laplace-Lagrange theory based on linear equations for Lagrange elements, the third-degree terms in orbital eccentricities and inclinations are taken into account in the equations. The corresponding improvement of the solution turns out to be essential in studying the evolution of orbits over long time intervals. A program inC has been written to calculate the corrections to the fundamental frequencies of the solution and the third-degree secular perturbations in orbital eccentricities and inclinations. The proposed method has been applied to investigate the motion of the major Uranian satellites. Over time intervals longer than 100 years, allowance for the nonlinear terms in the equations is shown to give corrections to the coordinates of Miranda on the order of the orbital eccentricity, which is several thousand kilometers in linear measure. For other satellites, the effect of allowance for the nonlinear terms turns out to be smaller. Obviously, when a general analytical theory of motion for the major Uranian satellites is constructed, the nonlinear terms in the equations for the secular perturbations should be taken into account.     

Orbital evolution of the distant satellites of the giant planets

We study the evolution of several distant satellite orbits. These are the orbits (including the improved ones)of the recently discovered Neptunian satellites S/2002 N1, N2, N3, N4; S/2003 N1 and the orbits of Jovian, Saturnian, and Uranian satellites with librational variations in the argument of the pericenter: S/2001 J10 (Euporie), S/2003 J20; S/2000 S5 (Kiviuq), S/2000 S6 (Ijiraq), and S/2003 U3. The study is performed using mainly an approximate numerical-analytical method. We determine the extreme eccentricities and inclinations as well as the periods of the variations in the arguments of pericenters and longitudes of the ascending nodes on time intervals ～10⁵?10⁶ yr. We compare our results with those obtained by numerically integrating the rigorous equations of satellite motion on time intervals of the order of the circulation periods of the longitudes of the ascending nodes (10²?10³ yr).     

天王星卫星两种定标方法测定结果的比较

利用新发表的高精度、高密度天体测量星表UCAC2,对天王星的五颗主要卫星的CCD观测图像重新进行量测,采用不同方法作定标归算,并使用两种理论模型(GUST86和GUST06模型)计算卫星的理论位置。对不同方法所得到的卫星位置的O-C结果的分析和比较表明,本文获得的卫星位置精度,除天卫五(Miranda)有显著提高,其他4颗卫星的位置精度基本相同。本文中天卫一和天卫三的结果与"亮卫星定标法"的结果在精度上相当,天卫二的位置精度与其他天王星卫星的位置精度具有较好的一致性,这从另一方面证明了我们的"亮卫星定标法"的可靠性。此外我们还获得了天卫四的位置与精度。     

Long-term evolution of the orbits of natural satellites

This review presents the recent works devoted to the construction or the improvement of the theories of motion of all natural planetary, satellites (except the Moon). The knowledge of the long-term evolution of these motions is strongly dependent on the accuracy of current theories. With the increasing precision of the ground-based observations, and with the past and future space missions, most of the theories have been or have to be revisited, taking into account more and more disturbing effects and specially tidal dissipation. These studies are often made difficult by the resonant behaviour of the system. We emphasize here tidal evolution in resonance. In the Jovian and Saturnian systems, tidal actions might explain the observed resonant state, as well as the heating of the satellites up to the softening and the resurfacing of some of them. However in the case of the Uranian satellites., no true resonance appears in spite of an observational evidence of tidal effects in resurfacing Ariel and Miranda, and new works try to expalin these differences.     

An attempt to build a new completely analytical theory of the Uranian satellites: The results achieved and the results to be obtained

An attempt to build a new theory of the main Uranian satellites is being made at the Sternberg Astronomical Institute. The main difference compared to GUST86 theory is that the new theory is planned to be completely analytical. To do this, the secular frequencies of the satellites should be calculated taking into account the secular perturbations of the second order and, partly, of the third order. This allows to improve the secular frequencies and make them more close to those obtained from numerical integration. Nevertheless, discrepancies remain, which indicate that more terms in the analytical development are needed. Some other advantages of the new theory are also discussed.     

On the orbits and masses of the satellites of the Pluto-Charon system

Two small satellites of Pluto, S/2005 P1 (hereafter P1) and S/2005 P2 (hereafter P2), have recently been discovered outside the orbit of Charon, and their orbits are nearly circular and nearly coplanar with that of Charon. Because the mass ratio of Charon-Pluto is ∼0.1, the orbits of P2 and P1 are significantly non-Keplerian even if P2 and P1 have negligible masses. We present an analytic theory, with P2 and P1 treated as test particles, which shows that the motion can be represented by the superposition of the circular motion of a guiding center, the forced oscillations due to the non-axisymmetric components of the potential rotating at the mean motion of Pluto-Charon, the epicyclic motion, and the vertical motion. The analytic theory shows that the azimuthal periods of P2 and P1 are shorter than the Keplerian orbital periods, and this deviation from Kepler's third law is already detected in the unperturbed Keplerian fit of Buie and coworkers. In this analytic theory, the periapse and ascending node of each of the small satellites precess at nearly equal rates in opposite directions. From direct numerical orbit integrations, we show the increasing influence of the proximity of P2 and P1 to the 3:2 mean-motion commensurability on their orbital motion as their masses increase within the ranges allowed by the albedo uncertainties. If the geometric albedos of P2 and P1 are high and of order of that of Charon, the masses of P2 and P1 are sufficiently low that their orbits are well described by the analytic theory. The variation in the orbital radius of P2 due to the forced oscillations is comparable in magnitude to that due to the best-fit Keplerian eccentricity, and there is at present no evidence that P2 has any significant epicyclic eccentricity. However, the orbit of P1 has a significant epicyclic eccentricity, and the prograde precession of its longitude of periapse with a period of 5300 days should be easily detectable. If the albedos of P2 and P1 are as low as that of comets, the large inferred masses induce significant short-term variations in the epicyclic eccentricities and/or periapse longitudes on the 400-500-day timescales due to the proximity to the 3:2 commensurability. In fact, for the maximum inferred masses, P2 and P1 may be in the 3:2 mean-motion resonance, with the resonance variable involving the periapse longitude of P1 librating. Observations that sample the orbits of P2 and P1 well on the 400-500-day timescales should provide strong constraints on the masses of P2 and P1 in the near future.