共查询到20条相似文献，搜索用时 751 毫秒
1.
Christoph Lhotka 《Celestial Mechanics and Dynamical Astronomy》2013,115(4):405-426
We derive a symplectic mapping model based on Hadjidemetriou’s method for the synchronous spin-orbit problem with and without the additional precession of the nodes. The mapping is derived from the averaged potential of the spin-orbit dynamical model and includes the main spin-orbit interactions, i.e. the non-zero obliquity and wobble motion of the rotating body. In addition the orbit of the perturbing body allows non-zero inclination and eccentricity. To obtain the equilibrium configuration we calculate the position and stability of the fixed points in the 1:1 spin-orbit resonance and relate them to the equilibria of the continuous system. We use the mapping equations to investigate the long-term stability close to the fixed point solutions of the mapping. We also apply the mapping method to the case of the moon Titan and validate the mapping approach by means of numerical integrations. The mapping model reproduces all the characteristics of Deprit’s model of free rotation as well as the dynamical features of Henrard’s averaged model of spin-orbit interaction with great precision. 相似文献
2.
Miquel Grau Guillermo González-Casado 《Celestial Mechanics and Dynamical Astronomy》1998,72(3):169-186
A comparative study of the evolution of the Sun–Jupiter–Asteroid system near the 4:1 and 7:2 resonances is performed by means
of two techniques that proceed differently from the Hamiltonian corresponding to the planar restricted elliptic three-body
problem. One technique is based on the classical Schubart averaging while the other is based on a mapping method in which
the perturbing part of the Hamiltonian is expanded and the resulting terms are ordered according to a weight function that
depends on the powers of eccentricities and the coefficients of the terms. For the mapping method the effect of Saturn on
the asteroidal evolution is introduced and the degree of chaos is estimated by means of the Lyapunov time. Both methods are
shown to lead to similar results and can be considered a suitable tool for describing the evolution of asteroids in the Kirkwood
gap and the group corresponding to the 4:1 and 7:2 Jovian resonances, respectively.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
The global validity of the symplectic integration method or mapping approach is discussed in this paper. The results show that in the regions of phase space where symplectic integration schemes and the Hamiltonian system possess the same topology, they are effective; but in the regions where the schemes possess some other fixed points than those of the Hamiltonian system, their topologies are different from that of the actual system, thus the symplectic integration method or mapping approach is not effective globally.Supported by the National Natural Science Foundation of China and a grant from the Ph.D. Foundation. 相似文献
4.
H. Varvoglis 《Astrophysics and Space Science》1985,109(2):395-397
It is shown that no conflicts need to arise between results on the stochastic properties of a dynamical system obtained through the method of the surface of section mapping and results obtained through the Hedlund-Hopf-Lobachevsky-Hadamard theorem. 相似文献
5.
V.S. Kalantonis E.A. Perdios A.E. Perdiou O. Ragos M.N. Vrahatis 《Astrophysics and Space Science》2003,288(4):489-497
The computation of periodic orbits of nonlinear mappings or dynamical systems can be achieved by applying a root-finding method. To determine a periodic solution, an initial guess should be located within a proper area of the mapping or a surface of section of the phase space of the dynamical system. In the case of Newton or Newton-like methods these areas are the basins of convergence corresponding to the considered solution. When several solutions of the same period exist in a particular region, then the deflation technique is suitable for the calculation of all these solutions. This technique is applied here to the Hénon's mapping and the driven conservative Duffing's oscillator. 相似文献
6.
R. R. Cordeiro R. S. Gomes R. Vieira Martins 《Celestial Mechanics and Dynamical Astronomy》1996,65(4):407-419
We present a method to construct a mapping for perturbed systems, in which the perturbations do not need to be conservative. We use a variation of Wisdom and Holman's method, where the dissipative term is placed together with the other perturbative terms. The method is applied for two dissipative systems: one including gas drag and the other including Poynting-Robertson drag. We compare the results with those obtained by Malhotra's mapping. Because the dissipative part in our method is treated as a regular perturbative term, there is no need for analytical developments of the nonconservative terms. This is a great advantage in itself and this also allows for a fast performance of the integrator. 相似文献
7.
8.
Yi-Sui Sun 《Celestial Mechanics and Dynamical Astronomy》1985,37(2):171-181
We study an extension of the Hénon mapping to a dissipative dynamical system with three-dimensions and discuss the behavior of the attractors of the Hénon mapping in the extended mapping $$T:\left\{ {\begin{array}{*{20}c} {X_{i + 1} = Y_i + 1 - AX_i^2 + C cos Z_i } \\ {Y_{i + 1} = BX_i + D \sin Z_i } \\ {Z_{i + 1} = Z_i + E \sin Y_{i + 1} + F, (\bmod 2\pi ).} \\ \end{array} } \right.$$ The results show that the strange attractor is destroyed by perturbed extension more easily than the trivial attractor and the invariant manifold of the conservative dynamical system. 相似文献
9.
回顾了作为实用天文学和大地测量学中基本研究课题之一的大气折射函数研究的最新进展;介绍了近几年发展的大气折射母函数方法。对如今广泛地应用在空间测量技术中的几种映射函数,如ＣｆＡ２．２、ＭＴＴ等模型作出评述;特别分析了ＮＭＦ模型的优点和不足之处。还介绍了由大气折射母函数方法引出的大气延迟新连分式映射函数和天文大气折射的映射函数方法,利用ＶＬＢＩ实验中高度截止角与基线长变化的关系和探空气球（ｒａｄｉｏｓ 相似文献
10.
Mineral mapping of the lunar surface is critical to understanding the Moon’s geological diversity and history, yet the global lunar abundance of minerals has not been mapped using hyperspectral data. The Interference Imaging Spectrometer (IIM) of Chang’E-1 mission obtained hyperspectral data of the global lunar surface within the wavelength of 480–960 nm in which major minerals can be discriminated by faint differences in 32 contiguous hyperspectral bands. The effect of space weathering produces multiple endmembers of lunar minerals by obscuring the pure spectra of minerals in different levels. In this study, the distributions of plagioclase, clinopyroxene and olivine on the global lunar surface were mapped with IIM hyperspectral data based on the modified Multiple Endmember Spectral Mixture Analysis (MESMA) method considering the space weathering effect. The distribution of lunar space weathering levels was retrieved as a byproduct of mineral mapping. The mineral mapping results were compared with recent mapping results. Although the wavelength of IIM is limited, it shows that our results are basically consistent with the recent research at both global and local scales. The distribution of space weathering levels is also consistent with the map of optical maturity parameter (OMAT) in most parts of the global lunar surface, especially in the highlands. This study demonstrates that the modified MESMA method is an effective approach to quantitative mapping of the lunar minerals and space weathering levels using hyperspectral data. In the future, more minerals can be mapped with higher accuracy if hyperspectral data with a wider spectral range are used based on the method proposed in this study. 相似文献
11.
12.
严豪健 《中国科学院上海天文台年刊》2004,(1)
回顾了作为实用天文学和大地测量学中基本研究课题之一的大气折射映射函数研究的进展。介绍了近几年上海天文台发展的大气折射母函数方法 ,以及由此导出的大气折射解析解。对如今广泛地应用在空间测量技术中的几种映射函数做出评述 ;分析了NMF模型的优点和不足之处。介绍了由大气折射母函数方法引出的大气延迟新连分式映射函数和天文大气折射的映射函数方法。利用VLBI实验中高度截止角与基线长度重复率的关系、探空气球 (radiosonde)观测资料、PRARE资料比较了各种映射函数的结果。特别指出了映射函数方法对天文大气折射和光学波段测距精度的改进。讨论了大气折射计算中的主要误差源。 相似文献
13.
K. G. Hadjifotinou John D. Hadjidemetriou 《Celestial Mechanics and Dynamical Astronomy》2002,84(2):135-157
A symplectic mapping is constructed for the study of the dynamical evolution of Edgeworth-Kuiper belt objects near the 2:3 mean motion resonance with Neptune. The mapping is six-dimensional and is a good model for the Poincaré map of the real system, that is, the spatial elliptic restricted three-body problem at the 2:3 resonance, with the Sun and Neptune as primaries. The mapping model is based on the averaged Hamiltonian, corrected by a semianalytic method so that it has the basic topological properties of the phase space of the real system both qualitatively and quantitatively. We start with two dimensional motion and then we extend it to three dimensions. Both chaotic and regular motion is observed, depending on the objects' initial inclination and phase. For zero inclination, objects that are phase-protected from close encounters with Neptune show ordered motion even at eccentricities as large as 0.4 and despite being Neptune-crossers. On the other hand, not-phase-protected objects with eccentricities greater than 0.15 follow chaotic motion that leads to sudden jumps in their eccentricity and are removed from the 2:3 resonance, thus becoming short period comets. As inclination increases, chaotic motion becomes more widespread, but phase-protection still exists and, as a result, stable motion appears for eccentricities up to e = 0.3 and inclinations as high as i = 15°, a region where plutinos exist. 相似文献
14.
The propagation and Poincaré mapping of perturbed Keplerian motion is a key topic in Celestial Mechanics and Astrodynamics, e.g., to study the stability of orbits or design bounded relative trajectories. The high-order transfer map (HOTM) method enables efficient mapping of perturbed Keplerian orbits using the high-order Taylor expansion of a Poincaré or stroboscopic map. The HOTM is only accurate close to the expansion point and therefore the number of revolutions for which the map is accurate tends to be limited. The proper selection of coordinates is of key importance for improving the performance of the HOTM method. In this paper, we investigate the use of different element sets for expressing the high-order map in order to find the coordinates that perform best in terms of accuracy. A new set of elements is introduced that enables extremely accurate mapping of the state, even for high eccentricities and higher-order zonal perturbations. Finally, the high-order map is shown to be very useful for the determination and study of fixed points and center manifolds of Poincaré maps. 相似文献
15.
Geophysical techniques based on radioactivity measurements are not generally used for exploration of asteroid impact craters. Our studies on the field and laboratory measurements of radioactivity on samples from the Lonar crater, India, show that this technique could be an important method for mapping the distribution of ejecta around the deeply excavated impact craters particularly when these structures are formed on relatively old target rocks/palaeosol. The Lonar ejecta shows ~1.3 times higher γ-ray count rates in the field on average compared to the underlying palaeosol and ~1.9 times higher values over the target basalt while measured by a portable Geiger–Müller pulse counter. The absorbed γ-dose rate (D) of the Lonar samples, computed from 232Th, 238U, and 40K abundances in these samples, also show that the ejecta has distinct bulk dose rates (average ~8.42 nGy h?1) as compared to those of the palaeosol (~18.34 nGy h?1), target basalt (~11.97 nGy h?1), and the impact-melts and spherules (~14 nGy h?1). Therefore, radioactivity mapping of the terrestrial and planetary impact craters by direct methods has importance in mapping ejecta distributions around these structures. 相似文献
16.
D. Lorenzetti R. Orfei P. Saraceno F. Strafella C. B. Cosmovici 《Astrophysics and Space Science》1983,90(1):171-178
A new near infrared spectrophotometer has been built for the Asiago 182 cm telescope. The instrument performs both large band JHKLM photometry and 1–5 spectrophotometry; a tracking system on a field star allows closed loop mapping. The design and performances are discussed. 相似文献
17.
Demands for a broad range of integrated geospatial data-analysis tools and methods for planetary data organization have been growing considerably since the late 1990s when a plethora of missions equipped with new instruments entered planetary orbits or landed on the surface. They sent back terabytes of new data which soon became accessible for the scientific community and public and which needed to be organized. On the terrestrial side, issues of data access, organization and utilization for scientific and economic analyses are handled by using a range of well-established geographic information systems (GIS) that also found their way into the field of planetary sciences in the late 1990s. We here address key issues concerning the field of planetary mapping by making use of established GIS environments and discuss methods of addressing data organization and mapping requirements by using an easily integrable datamodel that is—for the time being—designed as file-geodatabase (FileGDB) environment in ESRI's ArcGIS. A major design-driving requirement for this datamodel is its extensibility and scalability for growing scientific as well as technical needs, e.g., the utilization of such a datamodel for surface mapping of different planetary objects as defined by their respective reference system and by using different instrument data. Furthermore, it is a major goal to construct a generic model which allows to perform combined geologic as well as geomorphologic mapping tasks making use of international standards without loss of information and by maintaining topologic integrity. An integration of such a datamodel within a geospatial DBMS context can practically be performed by individuals as well as groups without having to deal with the details of administrative tasks and data ingestion issues. Besides the actual mapping, key components of such a mapping datamodel deal with the organization and search for image-sensor data and previous mapping efforts, as well as the proper organization of cartographic representations and assignments of geologic/geomorphologic units within their stratigraphic context. 相似文献
18.
Observation made at low evelation angles is the trend of development of GPS (Global Positioning System) meteorology, wherein the development of highly accurate atmospheric hydrostatic delay corrections at low elevating angles is the main key technique. The comparison among three methods for calculating the atmospheric hydrostatic delay correction of the radio waves from space to the ground-based receiver is made: (1) the atmospheric hydrostatic delay obtained from the path integration of the sounding balloon data under the assumption of atmospheric spherical symmetry, (2) the atmospheric hydrostatic delay acquired from the reanalyzed data of the NCEP (National Centers for Environmental Prediction) under the assumption of atmospheric spherical symmetry and (3) the atmospheric hydrostatic delay got from Niell's atmospheric hydrostatic mapping function. The results of the comparison of them with the atmospheric hydrostatic mapping function obtained from the calculation carried out by taking advantage of the data acquired at 89 sounding balloon stations in China in 2001 show that the accuracy of the method of the path integration of the reanalyzed data of NCEP at low elevating angles (bellow 5°) is about 5 times better than that of the Niell mapping function model. 相似文献
19.
C. Budtz-Jørgensen I. Kuvvetli N.J. Westergaard P. Jonasson V. Reglero C. Eyles T. Neubert 《Astrophysics and Space Science》2001,276(1):281-289
DSRI has initiated a development program of CZT X-ray and gamma raydetectors employing strip readout techniques. A dramatic improvement ofthe energy response was found operating the detectors as so-called driftdetectors. For the electronic readout, modern ASIC chips wereinvestigated. Modular design and the low power electronics will make largearea detectors using the drift strip method feasible. The performance of aprototype CZT system will be presented and discussed. One such detector system has been proposed for future space missions: TheX-Ray Imager (XRI) on the Atmospheric X-ray Observatory (AXO), whichis a mission proposed to the Danish Small Satellite Program and is dedicatedto observations of X-ray generating processes in the Earth's atmosphere. Ofspecial interest will be simultaneous optical and X-ray observations of spritesthat are flashes appearing directly above an active thunderstorm system.Additional objective is a detailed mapping of the auroral X-ray and opticalemission. XRI comprises a coded mask and a 20 cm × 40 cm CZTdetector array covering an energy range from 5 to 200 keV. 相似文献
20.
Ying-Ke Huang Yue-Dong Fang Kai-Xing Lu Zhi-Xiang Zhang Ji-Lin Liu Sha-sha Li Bao-Rui Luo Qin Lin Zhuo-Xi Huo 《天文和天体物理学研究(英文版)》2022,(3):100-114
Measuring quasar distance through joint analysis of spectroastrometry and reverberation mapping observations is a new method for driving the development of cosm... 相似文献