New confirmation of image-processing techniques for astrometry of Saturn and its satellites     

Q. Y. Peng 《Monthly notices of the Royal Astronomical Society》2005,359(4):1597-1600

The image-processing techniques used by Peng et al. are further improved to measure precisely the positions of Saturn and its satellites. 495 CCD images taken with the 1-m telescope at the Yunnan Observatory during the years 2002–2004 are processed with these techniques. These measured pixel positions are compared to their theoretical positions computed with the ephemerides of TASS1.7 for the satellites and JPL DE405 for Saturn itself. Analysis of the data for the intersatellite positions among four bright Saturnian satellites (S3–S6) and for Saturn–satellite (i.e. Saturn–Titan) positions shows that these measured positions have the same dispersions, i.e. about 0.05 and 0.06 arcsec in right ascension and declination, respectively. However, for the fainter satellites, Enceladus and Mimas, poorer residuals up to 0.1 and 0.2 arcsec, respectively, in both directions are found mainly due to their small separations from the primary planet and short exposure time in order to obtain useful images of Saturn.  相似文献   

Orbital evolution of Uranus’s new outer satellites     

M. A. Vashkov’yak 《Astronomy Letters》2001,27(6):404-409

Data on three recently discovered satellites of Uranus are used to determine basic evolutional parameters of their orbits: the extreme eccentricities and inclinations, as well as the circulation periods of the pericenter arguments and of the longitudes of the ascending nodes. The evolution is mainly investigated by analytically solving Hill’s double-averaged problem for the Uranus-Sun-satellite system, in which Uranus’s orbital eccentricity e _U and inclination i _U to the ecliptic are assumed to be zero. For the real model of Uranus’s evolving orbit with e _U≠0 and i _U≠0, we refine the evolutional parameters of the satellite orbits by numerically integrating the averaged system. Having analyzed the configuration and dynamics of the orbits of Uranus’s five outer satellites, we have revealed the possibility of their mutual crossings and obtained approximate temporal estimates.  相似文献   

Comments on Lambeck and Coleman: 'The Earth's shape and gravity field: a report of progress from 1958 to 1982'     

F. J. Lerch  S. M. Klosko  C. A. Wagner 《Geophysical Journal International》1986,86(2):651-664

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New constraints on Io's and Jupiter's tidal dissipation     

Valéry Lainey  Gabriel Tobie 《Icarus》2005,179(2):485-489

Although the quest for tidal accelerations among the Galilean satellites has been ongoing since the beginning of the last century, no real agreement has been found so far. Using a numerical approach, we simulate the effect of tidal interactions on the evolution of Io's motion during the last century. We show how these tidal effects can vanish during the fit process to observational data. By testing different values of dissipation within Io and Jupiter, we show that a non-detection of significant Io's orbital acceleration does not imply a large dissipation within Jupiter, and we suggest an upper bound value () for the dissipation rate within Io.  相似文献   

Folding of Europa's icy lithosphere: an analysis of viscous-plastic buckling and subsequent topographic relaxation     

Andrew J. Dombard  William B. McKinnon 《Journal of Structural Geology》2006,28(12):2259

Potential contractional folds on Jupiter's icy moon Europa have been identified. The best example is at the extensional band Astypalaea Linea, where a series of subtle topographic undulations, 25 km in wavelength, possess parasitic tectonic features that support a folding origin. A scenario has been qualitatively proposed, whereby folds form via unstable contraction of the icy lithosphere, compensate for extension elsewhere on Europa, and then subsequently relax. Here, we quantitatively address this scenario, applying a model for viscous-plastic buckling of planetary lithospheres and finite element simulations of topographic relaxation. Our results suggest that the lithosphere of Europa could indeed be unstable, but the low required surface temperatures limit fold formation to higher latitudes, and the high required driving stresses (9–10 MPa) are difficult to achieve on the satellite. The depth to the brittle–ductile transition is well constrained, and high thermal gradients are indicated, implying heat flows near 100 mW m⁻². In addition, topographic relaxation progresses so slowly even at these heat flows that it is not a viable mechanism to eliminate such features over the age of Europa's surface. Given the paucity of identified folds, we conclude that the necessary conditions for their formation are rare and that lithospheric folding is a minor mechanism for compensating the large amounts of extension seen elsewhere on Europa.  相似文献   

用基于Givens变换的QR分解计算类GPS广播星历参数   总被引：5，自引：0，他引：5  

崔先强  唐颖哲  姬剑锋  李舒侗 《测绘工程》2006,15(4):5-8

分析研究类GPS广播星历参数拟合算法的必要性,来介绍可用于解最小二乘问题的Givens变换,讨论使用Givens变换计算MEO和小倾角GEO卫星的类GPS广播星历参数的适用性,并用模拟数据进行验证。  相似文献   

利用C波段转发数据实现GEO卫星轨道确定     

毛悦  宋晓勇  贾小林  吴显兵  冯来平 《测绘科学技术学报》2012,29(3):175-178

为了提高我国卫星导航系统GEO卫星定轨能力,针对我国卫星导航系统所特有的新数据和新方法,利用CAPS系统的C波段转发式测距数据进行了单GEO卫星定轨实验.在分析该方法技术特点的基础上,从定轨残差和轨道重叠弧段比较等方面,对定轨结果进行了分析.由于设备转发时延是影响该方法定轨精度的重要因素,因此同时还分析了系统偏差对定轨精度的影响,得出了一些有益的结论.  相似文献   

北斗GEO卫星轨道算法研究   总被引：1，自引：0，他引：1  

刘季 《测绘信息与工程》2012,37(5):33-36

通过实际采集的北斗广播星历数据分析了GEO广播星历的相关轨道根数特性,北斗GEO卫星广播星历拟合坐标旋转法,给出了适用于北斗GEO卫星的轨道计算方法,通过理论分析和试验验证了北斗GEO法的可用性与正确性。  相似文献   

RESEARCH ON AUTOMATIC FOG IDENTIFICATION TECHNOLOGY BY METEOROLOGICAL SATELLITE REMOTE SENSING     

周红妹  葛伟强  柏桦  刘冬韡  杨引明 《热带气象学报(英文版)》2009,15(1):28-37

There is an urgent need for the development of a method that can undertake rapid, effective, and accurate monitoring and identification of fog by satellite remote sensing, since heavy fog can cause enormous disasters to China’s national economy and people's lives and property in the urban and coastal areas. In this paper, the correlative relationship between the reflectivity of land surface and clouds in different time phases is found, based on the analysis of the radiative and satellite-based spectral characteristics of fog. Through calculation and analyses of the relative variability of the reflectivity in the images, the threshold to identify quasi-fog areas is generated automatically. Furthermore, using the technique of quick image run-length encoding, and in combination with such practical methods as analyzing texture and shape fractures, smoothness, and template characteristics, the automatic identification of fog and fog-cloud separation using meteorological satellite remote sensing images are studied, with good results in application.  相似文献   

云的立体观测研究进展   总被引：1，自引：0，他引：1  

李艳兵  黄思训  翟景秋 《热带气象学报》2008,24(6):743-747

对云的立体观测的研究历史做了回顾,按照具有代表性的观测平台的变化划分了4个发展阶段,分别予以介绍,内容包括典型平台、技术途径和特点、同步精度、云高指定精度等。重点介绍了双星联合观测的云高指定技术,分析了关键技术和可能存在的问题,为技术实现做了较好的准备。  相似文献