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1.
Nikolay Emelyanov 《Planetary and Space Science》2010,58(3):411-420
Ephemerides of planetary satellites are needed to address many problems. These ephemerides are used for subsequent observations. A comparison of the available ephemerides with new observations allows the accuracy of the former to be assessed. However, the precision of the ephemerides must be known a priori when solving the tasks. In this paper we formulate and solve the problem of estimating the precision of the ephemerides of outer planetary satellites derived from observations when applied up to the future moments.The methods of assessing the precision of ephemerides involve producing a set of samples of the same ephemeris inferred from observations with different samples of Monte Carlo generated random errors (RO) superimposed onto it. The statistical parameters of simulated observational errors are based on the results of the reduction of real satellite observations. We compute the deviations of the samples of the ephemeris from the standard ephemeris inferred from real observations and adopt the root-mean-square deviation of the apparent coordinates as the precision of the ephemeris. We also use alternative methods: one based on the matrix of covariances of parameter errors (RP), and another one based on bootstrap samples of observations (BS).We use three methods (RO, RP, and BS) to estimate the precision of the ephemerides of all the 107 outer planetary satellites over the 2010-2020 time interval. The precision of the ephemerides of different satellites varies from 0.05 to 4.0 arcsec. For a number of satellites new observations are of vital importance for maintaining the precision of the ephemerides at a level that would allow identification of satellites during the reduction of observations. For some satellites the precision of their ephemerides is of the order of the sizes of their orbits and such satellites can be considered to have been lost. We show that the method of bootstrap samples (BS) can give doubtful results in the cases where there are few observations, which covered a time interval that is shorter than the orbital period of the satellite.Our results suggest obtaining more precise ephemeris making new observations at the times of maximum estimated errors of the ephemeris.All the inferred estimates of the precision of ephemerides are available from the MULTI-SAT ephemeris server: www.imcce.fr/sat (IMCCE), www.sai.msu.ru/neb/nss/index.htm (SAI). 相似文献
2.
N. V. Emels’yanov 《Solar System Research》2006,40(1):79-83
The upcoming epoch of rare events—that of mutual occultations and eclipses in the system of the major Uranian satellites—is reported. Such epochs last for four years and occur every 43 years. The ephemerides and circumstances for the events occurring during the 2006–2010 epoch are computed. The uniqueness and importance of observations of these events are emphasized. 相似文献
3.
More than 70 new distant satellites of major planets have been discovered over the past five years. Until recently, the Jet Propulsion Laboratory (JPL) in the USA was the only institution that modeled the motion of these satellites based on observational data and computed their ephemerides. New independent computations are needed to ensure the reliability and to assess the accuracy of satellite ephemerides. In this paper, the results of our determination of orbital parameters for 73 new distant satellites of major planets based on all available observations are reported and the adopted model of perturbing forces acting on a satellite is described. The satellite motions are computed via numerical integration. A special program—an ephemeris server—is used to compute the ephemerides of satellites, which are freely available to any user on the Internet at http://lnfm1.sai.msu.ru/neb/nss/index.htm. The server offers ample choice in terms of the form and composition of the ephemerides produced. The paper gives examples of deviations of the theory from observations and comparisons of our results with JPL ephemerides. Standard deviations of observational results from the theory are equal to 0.3–0.5 for most of the satellites. A comparison of our models of the motion of satellites with those developed at JPL shows that deviations in topocentric coordinates do not exceed 0.01 over a six-year interval.__________Translated from Astronomicheskii Vestnik, Vol. 39, No. 2, 2005, pp. 128–140.Original Russian Text Copyright © 2005 by Emelyanov, Kanter. 相似文献
4.
A. Vienne 《Planetary and Space Science》2008,56(14):1797-1803
Recently the motion of the main satellites of Jupiter, Saturn and Uranus have been modelled in order to get accurate ephemerides. These models have been fitted over a large amount of observations. Among these ones, the positions issued from the observations of mutual events are the most accurate. We can then expect to obtain a new kind of dynamical informations directly linked to planetological questions. We have to determine what information is used in these observations to get the still unknown dynamical parameters. We look after these questions especially in the Jovian and Saturnian systems. 相似文献
5.
天然卫星的位置测量在天体测量和天体力学中都有重要意义。国外有人对天王星卫星位置测量应用新的图象处理方法得到了高精度的卫星观测资料。利用云南天文台１米望远镜上获得的两颗卫星的ＳＲＴ的ＣＣＤ观测资料进行了新老图象处理方法的比较研究。当用两颗卫星直接作定标测量ＣＣＤ的比例尺和指向时表明：主星晕的处理对卫星位置的测量非常重要。去晕处理后,测得的比例尺和指向的弥散将大为减少。 相似文献
6.
Nikolay Emelyanov 《Planetary and Space Science》2008,56(14):1785-1790
We suggest a new approach and develop an original method for deriving astrometric data from the photometry of mutual occultations and eclipses of planetary satellites. We decide to model not the relative apparent motion of one satellite with respect to another satellite but the deflection of the observed relative motion with respect to the theoretical motion implied by appropriate ephemerides.We have attempted to reduce the results of photometric observations of the Gallilean satellites during their mutual occultations and eclipses in 2002-2003. The data of observation for 319 light curves of 106 mutual events were received from the observers. The reliable 245 light curves were processed with our method. Eighty six apparent relative positions have been obtained.Systematic errors arise inevitably while deriving astrometric data. Most of them are due to factors that are unrelated to the methods for deriving astrometric data. The systematic errors are more likely due to incorrect excluding the effect of background on photometric counts. In the case of mutual occultations, the flux drop is determined to a considerable degree by the ratio of the mean albedos of the two satellites. Some mutual event observations revealed wrong adopted values of the mean albedos. 相似文献
7.
现代天王星卫星运动定量理论的研究和发展 总被引：1，自引：0，他引：1
1986年“旅行者2号”飞越天于星期间，由空间无线电和光学观测获得的卫星资料首次给出天王星5颗主要卫星质量的可靠估计，从而推动了现代天王星卫星运动定量理论的建立。Laskar于1986年建立了第一个相对完整的天王星主要卫星的(半）分析理论——GUST86，其高精度已被许多学者的实算证实。之后，对理论的改进作出贡献的学者有：Malhotra等人(1989）、Lazzaro等人(1987，1991)分析研究了天王星卫星系统中近共振项对长期摄动解的影响；Taylor(1998)采用数值积分拟合观测资料，以更精确地测定卫星质量；Christou和Murray(1997)则将一个2阶Laplace—Lagrange理论应用于天王星卫星系统。对这些学者的工作作一概述。 相似文献
8.
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
9.
G. A. Kosmodamianskiy 《Astronomy Letters》2019,45(11):770-777
New versions of the ephemerides for the Galilean satellites of Jupiter (Io, Europa, Ganymede, and Callisto) constructed by numerically integrating the equations of motion of the satellites are presented. The satellite motionmodel takes into account the non-sphericity of Jupiter, the mutual perturbations of the satellites, and the perturbations from the Sun and major planets. The initial satellite motion parameters have been improved based on all the available series of ground-based optical observations spanning the interval 1891-2017, spacecraft observations, and radar observations. As a result, the coefficients of the expansion of the satellite coordinates and velocities in terms of Chebyshev polynomials in the interval 1891- 2025 have been obtained. The root-mean-square errors of the observations and the graphs of comparison of the constructed ephemerides both with the observations and with Lainey's numerical ephemerides are presented. The constructed ephemerides are publicly accessible. 相似文献
10.
11.
An accurate technique has been developed for measuring planetocentric positions of Jupiter's satellites from Wide Field/Planetary Camera images. Our method of finding the centers of the satellites and planet is based upon established limb-fitting techniques, but we have adapted those techniques to astrometry. We compare our limb-fitting results with previously published work and discuss its errors. A model ellipse is generated from the physical ephemeris of the planet including its phase defect. Then the planet center coordinates are computed by fitting the model to the limb observations using the method of least squares. A satellite position is determined similarly, and its offset from the planet is calculated. A total of 76 positions of the galileans satellites, the small moon Amalthea, and the shadows of Io and Ganymede cast on Jupiter have been measured on 61 images. Comparison between the observational results and JPL satellite ephemerides demonstrates the validity of this new method of analysis. The accuracy of the galilean satellite measurements is estimated to be 0.04 arcsec in right ascension and in declination. 相似文献
12.
C. Frederick Peters 《Celestial Mechanics and Dynamical Astronomy》1975,12(1):99-110
A general method is given for predicting eclipse events for natural planetary satellites suitable for use on a large scale digital computer. The precision is sufficient to process photometric eclipse observations to improve natural satellite ephemerides. Expected accuracy improvement for Saturn's satellites should be an order of magnitude or better. Predicted eclipse times of satellites by Saturn and the Rings are given for the next decade.Presented at IAU Colloquium No. 28, Ithaca, New York, August, 1974. 相似文献
13.
The occurrence of the Earth and Sun transits through the equatorial plane of Uranus will bring us the opportunity for observations only possible at that time: mutual events of the satellites, search for new faint satellites and measurement of the thickness of the rings.The predictions of the mutual events need a theoretical model of the motion of the satellites. The calculated occurrences of the occultations and eclipses highly depend on the model since these predictions are very sensitive to the relative positions of the satellites. A difference of 0.05 arcsec in latitude may make an event inexistent and the accuracy of the theoretical models is around 0.1 arcsec.In order to be sure of the occurrence of each event, we made the predictions using three theoretical models: the first one is GUST86 made by Laskar and Jacobson in 1986, the second is GUST06 based on the former model fitted by Emelianov on new observations and the third one is LA06 based on a brand new theory with an accuracy 10 times better than GUST and fitted on recent observations made since 1950.This comparison shows that some events predicted with one model are not predicted using another one. We try to select the events which will occur surely in order to help the observers to catch the best phenomena.The search for new satellites and the measurement of the thickness of the rings are planned by means of observations at the time of the transit of the Earth in the ring plane. 相似文献
14.
T. P. Kiseleva A. A. Kiselev O. A. Kalinichenko N. A. Vasilyeva M. L. Khovricheva 《Solar System Research》2008,42(5):414-433
The results of photographic observations of Jupiter’s Galilean satellites made with the 26-inch refractor at the Pulkovo Observatory from 1986 to 2005 are given. Satellite coordinates with respect to Jupiter and the mutual distances between the satellites have been determined. A scale-trale technique that does not require reference stars for the astrometric reduction of measurements has been used. The effect of the Jupiter phase has been taken into account in the jovicentric coordinates. The observation results have been compared with a modern theory of the Galilean satellites’ motions. Systematic observation errors depending on the observation technique have been studied. The intrinsic observation accuracy in the random quotient is characterized by the values 0.041″ over X and Y. The external accuracy of the relative Galilean satellite coordinates determined by comparing the observations with modern ephemerides turned out to be equal to 0.165″, 0.213″ for the Jovicentric coordinates and 0.134″, 0.170″ for the “satellite-satellite” coordinates. The highest accuracy of the relative satellite coordinates is reached at small distances between the satellites which are less than 100″: the corresponding mean-square errors of one observation are equal in to the external convergence to 0.050″, 0.070″. The results of photographic observations have been compared with the first CCD observations of the Jupiter satellites made in 2004 with the 26-inch refractor. 相似文献
15.
M. Yu. Khovritchev 《Monthly notices of the Royal Astronomical Society》2009,393(4):1353-1358
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. 相似文献
16.
D. V. Nikonchuk 《Astronomy Letters》2012,38(12):813-828
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. 相似文献
17.
A. L. Poroshina 《Astronomy Letters》2013,39(12):876-881
The ephemerides of satellites of major planets are needed in planning spacecraft missions both for studying the satellites themselves and for navigational support during the flights of spacecraft in the vicinity of planets. In addition, accurate numerical theories of motion of the natural satellites of major planets make it possible to increase the accuracy of the ephemerides of their central planets based on positional (photographic and CCD) observations of the satellites. Numerical theories of Neptune’s satellites, Triton and Nereid, constructed within the framework of the ERA software package developed at the Institute of Applied Astronomy of the Russian Academy of Sciences are presented. 相似文献
18.
L. Duriez 《Celestial Mechanics and Dynamical Astronomy》1987,43(1-4):331-348
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. 相似文献
19.
P. K. Seidelmann 《Celestial Mechanics and Dynamical Astronomy》1993,56(1-2):1-12
Planetary and satellite theories have been historically and are presently intimately related to the available computing capabilities, the accuracy of observational data, and the requirements of the astronomical community. Thus, the development of computers made it possible to replace planetary and lunar general theories with numerical integrations, or special perturbation methods. In turn, the availability of inexpensive small computers and high-speed computers with inexpensive memory stimulated the requirement to change from numerical integration back to general theories, or representative ephemerides, where the ephemerides could be calculated for a given date rather than using a table look-up process. In parallel with this progression, the observational accuracy has improved such that general theories cannot presently achieve the accuracy of the observations, and, in turn, it appears that in some cases the models and methods of numerical integration also need to be improved for the accuracies of the observations. Planetary and lunar theories were originally developed to be able to predict phenomena, and provide what are now considered low accuracy ephemerides of the bodies. This proceeded to the requirement for high accuracy ephemerides, and the progression of accuracy improvement has led to the discoveries of the variable rotation of the Earth, several planets, and a satellite. By means of mapping techniques, it is now possible to integrate a model of the motion of the entire solar system back for the history of the solar system. The challenges for the future are: Can general planetary and lunar theories with an acceptable number of terms achieve the accuracies of observations? How can numerical integrations more accurately represent the true motions of the solar system? Can regularly available observations be improved in accuracy? What are the meanings and interpretations of stability and chaos with respect to the motions of the bodies of our solar system? There has been a parallel progress and development of problems in dealing with the motions of artificial satellites. The large number of bodies of various sizes in the limited space around the Earth, subject to the additional forces of drag, radiation pressure, and Earth zonal and tesseral forces, require more accurate theories, improved observational accuracies, and improved prediction capabilities, so that potential collisions may be avoided. This must be accomplished by efficient use of computer capabilities. 相似文献
20.
T. P. Kiseleva S. M. Chanturiya T. A. Vasil’eva O. A. Kalinichenko 《Solar System Research》2012,46(6):436-441
We present and discuss the results of the astrometry project during which we observed the satellites of Mars, Jupiter, Saturn, Uranus, and Neptune at the Abastumani Astrophysical Observatory (Georgia) between 1983 and 1994. Observations at the Abastumani Observatory were performed with the double Zeiss astrograph (DZA: D/F = 400/3024 mm) and AZT-11 telescope (F = 16 m). We processed a large array of observations and determined exact coordinates of the planets and their satellites in a system of reference stars of modern catalogues as well as relative coordinates of the satellites. The results were compared with modern ephemerides using the MULTI-SAT software. The comparison enabled us to estimate the accuracy of observations (their random and systematic uncertainties) and the accuracy of modern theories of the motion of planets and their satellites. Random uncertainties of observations are estimated to be 0.10??C0.40?? for various objects and observational conditions. Observational results obtained for Uranus, Neptune and the satellites Titania and Oberon were shown to deviate appreciably and systematically from theories of their motion. The results of observations are presented in the Pulkovo database for Solar System bodies that is available at the website http://www.puldb.ru. 相似文献