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1.
虞南华 《中国科学院上海天文台年刊》2006,(1):17-25
海洋潮汐和大气、海洋、海冰之间存在复杂的相互作用,它对地球气候有复杂而深远的影响。海潮对流经大陆沿岸或大陆架的洋流有很强烈的作用。潮汐流产生混合湍动;潮汐耗散和内潮波效应对海洋环流的传输和循环也有一定的影响。1995年前后,使用TOPEX／POSEIDON测高卫星资料。建立了十多个海潮模型。研究表明,1994-1996年期间发展起来的正压波海潮模型在深海的精度为2—3cm,空间分辨率为50km量级,在浅海区域的精度显著下降。近年来运用更加成熟精细的流体动力学理论模型,在数据同化技术中使用时间跨度更长的测高资料,已经建立了一些改进的海潮模型。该文使用验潮站潮汐常数、测高资料以及交叉点资料,评估了6个海潮模型在浅海区域(包括中国海海域)的表现,以应用于今后对海平面的研究。初步分析表明,浅海区域的海平面高度的误差仍然相当显著。要发展海洋潮汐模型需要进一步减小潮汐混淆效应,提高长周期潮汐的精度,尤其在浅海区域。模型的改进必将增进对潮汐现象的认识,促进学科间进行相互融合和相互渗透的研究(例如潮汐摩擦引起的月球自转的长期缓慢减速、地球内部结构的物理学研究等)。 相似文献
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Temporal Variations in the Second-Degree Stokes Tesseral Geopotential Coefficients from Topex/Poseidon Altimetry 总被引：1，自引：0，他引：1
Burša Milan Kenyon Steve Kouba Jan Ŝíma Zdislav Vatrt Viliam Vítek Vojtêch Vojtíŝková Marie 《Earth, Moon, and Planets》2003,93(1):37-64
The TOPEX/POSEIDON (T/P) altimetry data set covering the periodof January 1, 1993 to January 3, 2001 was used to derive monthlyseries of the second-degree tesseral geopotential coefficients.To account for the sea water temperature variations, rathersimple models have been devised and discussed, describinglocalized as well as areal variations of sea water temperatureand heights. The second-degree tesseral coefficients have alsobeen shown to be proportional to the pressureportions of the oceanic equatorial effective excitation functions,used in Ocean Angular Momentum (OAM) data. OAM datatogether with Atmospheric Angular Momentum (AAM) data canbe used to study observed polar motion (PM) series.The excess PM rates, derived from the T/P effective excitationfunctions, were compared to the corresponding observed PM rates,derived from the International Earth Rotation Service (IERS)Bulletin A and corrected with AAM also obtainedfrom IERS. The noise of the T/P derived PM rate series was foundto be significantly larger than the corresponding Bulletin A/AAMPM rate residuals as well as the PM rates derived from anindependent OAM series that was also available for the1993–2000 period. 相似文献
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大气、陆地水储量和海水质量分布变化与地球低阶引力场球谐系数的关系 总被引：4，自引：1，他引：3
大气、固体地球及海洋组成了一个复杂、变化的地球动力学系统，这一系统中的任一质量分布变化都将产生地球引力场变化。采用全球7000多个地面气象台站的月平均降水及温度资料、NCEP提供气压月均值、TOPEX／Poseidon卫星测高资料和WOA98海水温度及盐度模型计算了大气、陆地水储量和海水质量分布变化引起地球低阶引力场系数变化。比较综合大气、陆地水储量和海水质量分布变化对带谐项J2，J3，J4影响的计算结果和人卫激光卫星的测定结果，可以看出，大气、陆地水储量和海水质量分布变化是引起地球低阶引力场系数周年变化的重要激发源。 相似文献
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Burša Milan Kenyon Steve Kouba Jan Müller Achim Raděj Karel Vatrt Viliam Vojtíšková Marie Vítek Vojtěch 《Earth, Moon, and Planets》1999,84(3):163-176
The TOPEX/POSEIDON (T/P) satellite altimeter data from January 1, 1993to October 24, 1999 (cycles 11–261) was used for investigating
thelong-term variations in the geoidal geopotential W0 and/orin the geopotential scale factor R0 = GM/W0 (GM is theadopted geocentric gravitational constant). The mean valuesdetermined for the whole period covered are: W0 =(62 636 856.161 ± 0.002) m2 s-2, R0 =(6 363 672.5448 ± 0.0002) m. The actual accuracy is limited bythe altimeter calibration error (2–3 cm) and it isestimated
to be about ± 0.5 m2 s-2 (± 5 cm).The yearly variations of the above mean values are at the formalerror level. No long-term trend in W0, representing the oceanvolume change, was found for the seven years period 1993–9 on thebasis of T/P altimeter (AVISO) data.
No sea surface topography modelwas used in the solution.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
M. Vetrisano W. Van der Weg M. Vasile 《Celestial Mechanics and Dynamical Astronomy》2012,114(1-2):25-53
This paper presents a navigation strategy to fly to the Moon along a Weak Stability Boundary transfer trajectory. A particular strategy is devised to ensure capture into an uncontrolled relatively stable orbit at the Moon. Both uncertainty in the orbit determination process and in the control of the thrust vector are included in the navigation analysis. The orbit determination process is based on the definition of an optimal filtering technique that is able to meet accuracy requirements at an acceptable computational cost. Three sequential filtering techniques are analysed: an extended Kalman filter, an unscented Kalman filter and a Kalman filter based on high order expansions. The analysis shows that only the unscented Kalman filter meets the accuracy requirements at an acceptable computational cost. This paper demonstrates lunar weak capture for all trajectories within a capture corridor defined by all the trajectories in the neighbourhood of the nominal one, in state space. A minimum Δv strategy is presented to extend the lifetime of the spacecraft around the Moon. The orbit determination and navigation strategies are applied to the case of the European Student Moon Orbiter. 相似文献
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We use two independent General Circulation Models (GCMs) to estimate surface winds at Titan’s Ligeia Mare (78° N, 250° W), motivated by a proposed mission to land a floating capsule in this ～500 km hydrocarbon sea. The models agree on the overall magnitude (～0.5–1 m/s) and seasonal variation (strongest in summer) of windspeeds, but details of seasonal and diurnal variation of windspeed and direction differ somewhat, with the role of surface exchanges being more significant than that of gravitational tides in the atmosphere. We also investigate the tidal dynamics in the sea using a numerical ocean dynamics model: assuming a rigid lithosphere, the tidal amplitude is up to ～0.8 m. Tidal currents are overall proportional to the reciprocal of depth—with an assumed central depth of 300 m, the characteristic tidal currents are ～1 cm/s, with notable motions being a slosh between Ligeia’s eastern and western lobes, and a clockwise flow pattern.We find that a capsule will drift at approximately one tenth of the windspeed, unless measures are adopted to augment the drag areas above or below the waterline. Thus motion of a floating capsule is dominated by the wind, and is likely to be several km per Earth day, a rate that will be readily measured from Earth by radio navigation methods. In some instances, the wind vector rotates diurnally such that the drift trajectory is epicyclic. 相似文献
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E. L. Akim G. S. Zaslavsky I. M. Morskoy E. G. Ruzsky V. A. Stepaniants A. G. Tuchin 《Solar System Research》2010,44(1):26-37
This paper is concerned with the problems of ballistics, navigation, and flight control of the space craft (SC) in the Phobos-Grunt
mission. We consider an insertion into the Earth-Mars transfer trajectory, the Earth-Mars transfer, the strategy of corrections,
and the accuracy of the insertion of the SC into Martian orbit. During the orbital maneuvering stage in the sphere of influence
of Mars, we set up a scheme that allows for the insertion of the SC, with the prescribed accuracy, into a point 80-km above
the Phobos surface over the theoretical landing area. We specify the sequence for a controlled landing and provide methods
for solving the problems of navigation and control during a self-c ontained landing. We also consider the liftoff from Phobos,
insertion into the parking orbit, and the Mars-Earth transfer. 相似文献
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导航战背景下的天文导航技术—天文导航技术的历史、现状及其发展趋势 总被引：4，自引：0，他引：4
综述近30年来我国内外天文导航技术及其相关理论和方法的进展，介绍世界各军事大国对天文导航的认识，并就天文导航在导航战背景下的显著优势进行论述。包括下列主要内容：（1）天文导航设备的历史和现状；（2）天文导航理论的新成果；（3）各军事大国对天文导航的态势；（4）天文导航的优势性；（5）天文导航自动化的主要关键技术，（6）天文导航自动化技术的发展趋势。 相似文献
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海洋卫星测高技术的新进展 总被引：1，自引：0，他引：1
主要介绍９０年代发射的新一代海洋测高卫星。ＴＯＰＥＸ／ＰＯＳＥＩＤＯＮ卫星和ＥＲＳ－１卫星的情况。在简要说明这两颗测高卫星的主要任务和星载科学研究仪器之后，叙述了轨道选择的原理和精密轨道确定的情况，并介绍了最近国外利用ＴＯＰＥＸ／ＰＯＳＥＩＤＯＮ资料进行的海洋学研究和成果以及未来的测高计划。 相似文献
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Periodic polar motions caused by ocean tides are predicted. In the Liouville equations for rotational motion the complete excitation functions for the ocean tides have to be used. This does not depend on the fact that hydrodynamical ocean tide models do not consider the centrifugal acceleration. The observable polar motion of the Celestial Ephemeris Pole CEP (more exactly: the terrestrial location of the CEP) is tabulated for the ten ocean tides M2, S2, N2, K1, O1, P1, M f, M f′, M m, Ssa. Typical amplitudes for the largest ocean tides are 0.4 milliarcseconds. This is within the reach of geodetic VLBI and SLR observations. 相似文献
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《Planetary and Space Science》2007,55(13):1877-1885
Cassini/Huygens, a flagship mission to explore the rings, atmosphere, magnetic field, and moons that make up the Saturn system, is a joint endeavor of the National Aeronautics and Space Administration, the European Space Agency, and Agenzia Spaziale Italiana. Comprising two spacecraft—a Saturn orbiter built by NASA and a Titan entry/descent probe built by the European Space Agency—Cassini/Huygens was launched in October 1997. The Huygens probe parachuted to the surface of Titan in January 2005. During the descent, six science instruments provided in situ measurements of Titan's atmosphere, clouds, and winds, and photographed Titan's surface. To correctly interpret and correlate results from the probe science experiments, and to provide a reference set of data for ground-truth calibration of orbiter remote sensing measurements, an accurate reconstruction of the probe entry and descent trajectory and surface landing location is necessary. The Huygens Descent Trajectory Working Group was chartered in 1996 as a subgroup of the Huygens Science Working Team to develop and implement an organizational framework and retrieval methodologies for the probe descent trajectory reconstruction from the entry altitude of 1270 km to the surface using navigation data, and engineering and science data acquired by the instruments on the Huygens Probe. This paper presents an overview of the Descent Trajectory Working Group, including the history, rationale, goals and objectives, organizational framework, rules and procedures, and implementation. 相似文献
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Earth-based spacecraft tracking data have historically been processed with classical least squares filtering techniques both for navigation purposes and for physical constant determination. The small, stochastic non-gravitational forces acting on the spacecraft are described to motivate the use of sequential estimation as an alternative to the least squares fitting procedures. The stochastic forces are investigated both in terms of their effect on the tracking data and their influence on estimation accuracy. A flexiible sequential filter design which leaves the existing trajectory, variational equations, data observable and partial computations undisturbed is described. A detailed filter design is presented that meets the precision demands and flexibility requirements of deep space navigation and scientific problems, one which provides a high degree of numerical integrity and numerical analysis capability, facilitates the efficient computation of multiple solutions, and makes few demands on the supporting computational structure.This paper presents the results of one phase of research carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. NAS 7-100, sponsored by NASA. 相似文献
15.
The origin of the Earth's ocean has been discussed on the basis of deuterium/hydrogen ratios (D/H) of several sources of water in the Solar System. The average D/H of carbonaceous chondrites (CC's) is known to be close to the current D/H of the Earth's ocean, while those of comets and the solar nebula are larger by about a factor of two and smaller by about a factor of seven, respectively, than that of the Earth's ocean. Thus, the main source of the Earth's ocean has been thought to be CC's or adequate mixing of comets and the solar nebula. However, those conclusions are correct only if D/H of water on the Earth has remained unchanged for the past 4.5 Gyr. In this paper, we investigate evolution of D/H in the ocean in the case that the early Earth had a hydrogen-rich atmosphere, the existence of which is predicted by recent theories of planet formation no matter whether the nebula remains or not. Then we show that D/H in the ocean increases by a factor of 2-9, which is caused by the mass fractionation during atmospheric hydrogen loss, followed by deuterium exchange between hydrogen gas and water vapor during ocean formation. This result suggests that the apparent similarity in D/H of water between CC's and the current Earth's ocean does not necessarily support the CC's origin of water and that the apparent discrepancy in D/H is not a good reason for excluding the nebular origin of water. 相似文献
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One of the previously published models for the fragmentation of meteoroids (Baldwin and Sheaffer, 1971) is used to analyze the observed segment of the trajectory of Beneov's bolide (Beneov, EN 070591) of the European Fireball Network. An important element of these observations is the separation of luminous fragments from the main body at the final radiation stage of the bolide as a whole. The application of the least-squares method with the use of various models as trial functions shows that the model of a single body with ablation provides the best fit to the observed trajectory. 相似文献
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George H. Born 《Celestial Mechanics and Dynamical Astronomy》1970,2(1):103-113
In this paper, a combination analytical-numerical integration method for solving the differential equations of a modified set of Lagrange's planetary equations is described. The integration method is an Encke-type method because it involves integrating the deviations between the actual trajectory and a reference trajectory. The reference trajectory is obtained from an analytical solution containing the dominant secular and periodic effects of the gravitational field of the primary body. A set of nonsingular elements is used so that the method will be valid for all circular and elliptical motions. It is shown that the method is an accurate and efficient means of satellite ephemeris generation.This paper was presented at the AIAA/AAS Meeting, Princeton University, August 1969. 相似文献
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伽利略探测获得了木卫二的最新探测资料，其更精确的重力探测数据使深入研究木卫二的内部结构成为可能，研究表明，木卫二有着比较复杂的内部结构，最外层是水冰层，中层是岩石幔，中心是金属核（Fe或Fe-FeS)。但重力探测数据并不能确定水冰层中水的物态。多方面的证据（如理论，地学，磁场等证据）都表明木卫二的表面冰层下存在液体的导电海洋层，其中磁场方面的证据可能最为有力，概述了对木卫地的内部结构模型和海洋层两方面的研究，并推断潮汐演化是木卫二海洋层存在重要原因。 相似文献
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B. E. Schutz 《Celestial Mechanics and Dynamical Astronomy》1996,66(1):79-85
Modern observational techniques using ground-based and space-based instrumentation have enabled the measurement of the distance between the instrument and satellite to better than one centimeter. Such high precision instrumentation has fostered applications with centimeter-level requirements for satellite position knowledge. The determination of the satellite position to such accuracy requires a comparable modeling of the forces experienced by the satellite, especially when classical orbit determination methods are used. Geodetic satellites, such as Lageos, in conjunction with high precision ground-based laser ranging, have been used to improve for modeling of forces experienced by the satellite. Space-based techniques, such as Global Positioning System (GPS), offer alternatives, including kinematic techniques which require no modeling of the satellite forces, or only rudimentary models. This paper will describe the various techniques and illustrate the accuracies achieved with current satellites, such as TOPEX/POSEIDON, GPS/MET and the expectations for some future satellites. 相似文献