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1.
N. Delsate P. Robutel A. Lemaître T. Carletti 《Celestial Mechanics and Dynamical Astronomy》2010,108(3):275-300
We hereby study the stability of a massless probe orbiting around an oblate central body (planet or planetary satellite) perturbed
by a third body, assumed to lay in the equatorial plane (Sun or Jupiter for example) using a Hamiltonian formalism. We are
able to determine, in the parameters space, the location of the frozen orbits, namely orbits whose orbital elements remain
constant on average, to characterize their stability/unstability and to compute the periods of the equilibria. The proposed
theory is general enough, to be applied to a wide range of probes around planet or natural planetary satellites. The BepiColombo
mission is used to motivate our analysis and to provide specific numerical data to check our analytical results. Finally,
we also bring to the light that the coefficient J
2 is able to protect against the increasing of the eccentricity due to the Kozai-Lidov effect and the coefficient J
3 determines a shift of the equilibria. 相似文献
2.
3.
A. Lemaître 《Celestial Mechanics and Dynamical Astronomy》1984,32(2):109-126
This paper consists in analyzing very simple resonance models for the j+i/j (i=2, 3, 4) resonance cases by averaging, truncating and scaling the restricted three body problem. The phase space, the equilibria, the critical areas and the probability of capture are analytically calculated for each case. 相似文献
4.
The dynamics of space debris with very high A/m near the geostationary orbit is dominated by the gravitational coefficient C
22 and the solar radiation pressure. An analysis of the stability of the orbits by the chaos indicator MEGNO and frequency analysis map FAM shows chaotic layers around the separatrix and reveals a web of sub-structures associated to resonances with the annual period
of the Sun. This succession of stable thin islands and chaotic layers can be reproduced and explained by a quite simple toy
model, based on a pendulum approach, perturbed, through the eccentricity, by the external (Sun) frequency. The use of suitable
action-angle variables in the circulation and libration regions of the pendulum allows to point out new resonances between
the geostationary libration angle and the Sun’s longitude. They correspond very well (positions, shape, width) to the structures
visible on the FAM representations. 相似文献
5.
Julien Dufey Anne Lemaître Nicolas Rambaux 《Celestial Mechanics and Dynamical Astronomy》2008,101(1-2):141-157
Two space missions dedicated to Mercury (MESSENGER and BepiColombo) aim at understanding its rotation and confirming the existence of a liquid core. This double challenge requires much more accurate models for the spin-orbit resonant rotation of Mercury. The purpose of this paper is to introduce planetary perturbations on Mercury’s rotation using an analytical method and to analyse the influence of the perturbations on the libration in longitude. Applying a perturbation theory based on the Lie triangle, we were able to re-introduce short periodic terms into the averaged Hamiltonian and to compute the evolution of the rotational variables. The perturbations on Mercury’s forced libration in longitude mainly come from the orbital motion of Mercury (with an amplitude around 41 arcsec that depends on the momenta of inertia). It is completed by various effects from Jupiter (11.86 and 5.93 year-periods), Venus (with a 5.66 year-period), Saturn (14.73 year-period), and the Earth (6.58 year-period). The amplitudes of the oscillations due to Jupiter and Venus are approximately 33% and 10% of those from the orbital motion of Mercury and the amplitudes of the oscillations due to Saturn and the Earth are approximately 3% and 2%. We compare the analytical results with the solution obtained from the spin-orbit numerical model SONYR. 相似文献
6.
Nawal Alfarrah Gebremedhin Berhane Abdelrahim Hweesh Kristine Walraevens 《Ground water》2017,55(4):593-601
The desert of eastern Libya forms one of the most arid regions of the Sahara. The Great Man‐Made River Project (GMRP) was established. It transports millions of cubic meters of water a day from desert wellfields to the coastal cities, where over 80% of the population lives. The Tazerbo Wellfield is one of the wellfields designed within the GMRP, delivering water to the eastern coast of Libya through an underground pipe network. Tazerbo Wellfield consists of 108 production wells; each well was designed to pump 100 L/s. The planned total groundwater withdrawal from all wells is 1 million m3/d. The deep sandstone aquifer (Nubian sandstone) is covered by a thick mudstone‐siltstone aquitard and is being heavily pumped. The aquifer and fine‐grained sediments of the aquitard may be compacted resulting in land subsidence as a result of high exploitation. Local sinkholes have developed in the area of Tazerbo since the start of the pumping from the wellfield in 2004. These sinkholes have been caused mainly by lowering of the piezometric heads due to the withdrawal of groundwater. In this study, a hydrogeological investigation is presented about the effect of large groundwater pumping from the Nubian sandstone aquifer in Tazerbo Wellfield, SE Libya, based on physical parameters for 108 production wells and 23 observation wells. 相似文献
7.
Direct solar radiation pressure and Earth’s shadow crossings are known to be responsible for short-term variations of space debris orbital elements, the higher the area-to-mass ratio the larger the perturbation. Nevertheless, existing studies have always been performed on periods of time shorter than 150 years. Considering longer time scales of the order of a 1000 years, this paper focuses on the long-term periodic evolution of space debris trajectories caused by successive Earth’s shadow crossings. Other perturbations as the geopotential and third-body gravitational attractions obviously play a role and compete with the one which is described in this paper. Symplectic numerical propagations and new (semi-)analytical models are developed to identify a frequency associated to shadow entry and exit eccentric anomalies. It is shown that Earth’s shadow is responsible for large deviations from the initial orbital elements, even on shorter period of times, and that this effect increases along with the area-to-mass ratio. 相似文献
8.
Summary This paper deals with the first results concerning mesoscale ageostrophic circulations as they were presented during the International Meeting on Fronts and Orography, held in Burghausen, Germany, on June 1991. The aim is to test the importance of some specific small scale and mesoscale processes on the observed ageostrophic circulations. For this, various available theoretical models including these processes are used, in order to put in evidence their effect or to diagnose their presence or not in the observed circulations. These secondary circulations have been observed in the vicinity of two surface cold fronts documented during the European experiment FRONTS87 and they are quantitatively evaluated and compared with the theoretical ones. The diagnoses are performed by numerically solving two versions of the two-dimensional Sawyer-Eliassen equation for the ageostrophic streamfunction: a form based upon the Geostrophic Momentum approximation of along-front geostrophy and a Primitive Equation form that allows the existence of a along-front ageostrophic component. A simple parameterization of the Ekman pumping effect in the secondary circulations is added, through a boundary condition in the Sawyer-Eliassen equation resolution.This application of the Sawyer-Eliassen equation to measured data from a network of two or three sounding stations allows the identification of the significant frontogenetic terms and the testing of the assumptions underlying this diagnostic tool. Also, the impact of various parameterizations is considered. For instance, the introduction of a boundary layer parameterization scheme permits the reproduction of low-level updrafts observed in reality ahead of the frontal zone and predicted by numerical models found in literature.With 18 Figures 相似文献
9.
Mohamed G Abdelsalam Robert J Stern Woldegabriel G Berhane 《Journal of African Earth Sciences》2000,30(4):2037
Massive sulphide deposits in the Neoproterozoic Arabian-Nubian Shield are exposed at the surface as Fe-rich crusts termed gossans. Gossans are typically a few tens of metres across but are surrounded by wider clay- and Fe-rich alteration zones. Although Fe-rich gossans have characteristic reflectance spectra and surface roughness, they are often too small to be directly detected by Landsat TM or SIR-C images, both of which have about 30 m spatial resolution. In this paper, a procedure is described whereby gossans and the surrounding alteration zones can be identified and mapped by Landsat TM and SIR-C data using the Beddaho Alteration Zone and the Tebih Gossan in northern Eritrea as an example. Clay and Fe alteration index maps were generated by density slicing for Landsat TM band-ratios
and
, respectively. Landsat 5/7-4/5-3/1 TM images characteristically depict small (tens of pixels) gossans in blue and the more extensive alteration zones in pinkish purple. Chh-LhhLhh/Chh SIR-C images succeeded in identifying the gossan due to enhanced back-scattering of the radar shorter wavelength (6 cm) C-band by the rough gossan surfaces. This enhanced back-scattering might also be partially due to the characteristic dielectric property of the Fe-rich minerals forming the gossans. Choosing known gossans from both 5/7-4/5-3/1 Landsat TM and Chh-Lhh-Lhh/Chh SIR-C images as training sites for supervised classification helped to outline areas with reflectance spectra and radar back-scattering properties similar to those of the training sites. These results show significant correlation between supervised classifications based on the two data sets, suggesting a way to use combined visible and near infrared (VNIR) and radar imagery to explore for mineral deposits in arid regions. 相似文献
10.
The symmetric trace free (STF) tensor formalism, developed by Hartmann et al. (Celest Mech Dyn Astron 60:139–159. doi:10.1007/BF00693097, 1994), is a nice tool, not much used in Celestial Mechanics. It is fully equivalent to the usual spherical harmonics but permits more elegant and compact formulations. The coupling between the gravitational fields of extended bodies with this formalism has been used in Mathis and Le Poncin-Lafitte (Astron Astrophys 497:889–910. doi:10.1051/0004-6361/20079054, 2009) for binary stars or planetary systems, but not yet applied to binary asteroids. However, binary asteroids are common in the Solar System and usually their study requires a full two rigid body approach. The formulation of the two-body interaction potential in the STF formalism in the full two rigid body problem is detailed and completed in this article. An application to the binary asteroid (66391) 1999 KW4 is presented with a comparison of our results with other results of the literature for validation. 相似文献