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1.
The orbits of planetcrossing asteroids (and comets) can undergo close approaches and collisions with some major planet. This introduces a singularity in the Nbody Hamiltonian, and the averaging of the equations of motion, traditionally used to compute secular perturbations, is undefined. We show that it is possible to define in a rigorous way some generalised averaged equations of motion, in such a way that the generalised solutions are unique and piecewise smooth. This is obtained, both in the planar and in the threedimensional case, by means of the method of extraction of the singularities by Kantorovich. The modified distance used to approximate the singularity is the one used by Wetherill in his method to compute probability of collision. Some examples of averaged dynamics have been computed; a systematic exploration of the averaged phase space to locate the secular resonances should be the next step.'Alice sighed wearily. I think you might do something better with the time she said, than waste it asking riddles with no answers(Alice in Wonderland, L. Carroll) 相似文献
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Lorenzo Iorio 《Celestial Mechanics and Dynamical Astronomy》2001,79(3):201-230
The general relativistic Lense—Thirring effect can be measured by inspecting a suitable combination of the orbital residuals of the nodes of LAGEOS and LAGEOS II and the perigee of LAGEOS II. The solid and ocean Earth tides affect the recovery of the parameter by means of which the gravitomagnetic signal is accounted for in the combined residuals. Thus an extensive analysis of the perturbations induced on these orbital elements by the solid and ocean Earth tides is carried out. It involves the l=2 terms for the solid tides and the l=2,3,4 terms for the ocean tides. The perigee of LAGEOS II turns out to be very sensitive to the l=3 part of the ocean tidal spectrum, contrary to the nodes of LAGEOS and LAGEOS II. The uncertainty in the solid tidal perturbations, mainly due to the Love number k
2, ranges from 0.4% to 1.5%, while the ocean tides are uncertain at 5–15% level. The obtained results are used in order to check in a preliminary way which tidal constituents the Lense-Thirring shift is sensitive to. In particular it is tested if the semisecular 18.6-year zonal tide really does not affect the combined residuals. It turns out that, if modeled at the level of accuracy worked out in the paper, the l=2,4 m=0 and also, to a lesser extent, the l=3, m=0 tidal perturbations cancel out.This revised version was published online in October 2005 with corrections to the Cover Date. 相似文献
4.
Differential equations ruling the Earth’s polar motion are slightly asymmetric with respect to the pole coordinates. This is not only associated with the lack of axial symmetry around the Earth figure axis (triaxiality) but also with the longitude dependency of the pole tide (the main contribution). We propose a consistent handling of both asymmetric contributions, formulating a unique equation in the complex equatorial plane, of which we derive a general solution. Difference with respect to the usual symmetric solution is discussed and found significant in light of the present accuracy of the observed pole coordinates. For the same geophysical excitation, the prograde Chandler wobble is accompanied by a retrograde component up to 2 milliarcseconds (mas), transforming it in a slight elliptic motion. The asymmetric contribution is relatively larger in the geodetic excitation function, for Chandler wobble excitation mixes prograde and retrograde components of comparable level (1 mas). 相似文献
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Alejandro M. Leiva Carlos Bruno Briozzo 《Celestial Mechanics and Dynamical Astronomy》2008,101(3):225-245
Starting from 80 families of low-energy fast periodic transfer orbits in the Earth–Moon planar circular Restricted Three Body
Problem (RTBP), we obtain by analytical continuation 11 periodic orbits and 25 periodic arcs with similar properties in the
Sun–Earth–Moon Quasi-Bicircular Problem (QBCP). A novel and very simple procedure is introduced giving the solar phases at
which to attempt continuation. Detailed numerical results for each periodic orbit and arc found are given, including their
stability parameters and minimal distances to the Earth and Moon. The periods of these orbits are between 2.5 and 5 synodic
months, their energies are among the lowest possible to achieve an Earth–Moon transfer, and they show a diversity of circumlunar
trajectories, making them good candidates for missions requiring repeated passages around the Earth and the Moon with close
approaches to the last. 相似文献
6.
In the present paper the equations of the orbital motion of the major planets and the Moon and the equations of the three–axial
rigid Earth’s rotation in Euler parameters are reduced to the secular system describing the evolution of the planetary and
lunar orbits (independent of the Earth’s rotation) and the evolution of the Earth’s rotation (depending on the planetary and
lunar evolution). Hence, the theory of the Earth’s rotation can be presented by means of the series in powers of the evolutionary
variables with quasi-periodic coefficients with respect to the planetary–lunar mean longitudes. This form of the Earth’s rotation
problem is compatible with the general planetary theory involving the separation of the short–period and long–period variables
and avoiding the appearance of the non–physical secular terms. 相似文献
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G. Mingotti F. Topputo F. Bernelli-Zazzera 《Celestial Mechanics and Dynamical Astronomy》2011,110(2):169-188
In this paper novel Earth–Mars transfers are presented. These transfers exploit the natural dynamics of n-body models as well as the high specific impulse typical of low-thrust systems. The Moon-perturbed version of the Sun–Earth
problem is introduced to design ballistic escape orbits performing lunar gravity assists. The ballistic capture is designed
in the Sun–Mars system where special attainable sets are defined and used to handle the low-thrust control. The complete trajectory
is optimized in the full n-body problem which takes into account planets’ orbital inclinations and eccentricities. Accurate, efficient solutions with
reasonable flight times are presented and compared with known results. 相似文献
8.
Processes such as the solar wind sputtering and micrometeorite impacts can modify optical properties of surfaces of airless bodies. This explains why spectra of the main belt asteroids, exposed to these ‘space weathering’ processes over eons, do not match the laboratory spectra of ordinary chondrite (OC) meteorites. In contrast, an important fraction of Near Earth Asteroids (NEAs), defined as Q-types in the asteroid taxonomy, display spectral attributes that are a good match to OCs. Here we study the possibility that the Q-type NEAs underwent recent encounters with the terrestrial planets and that the tidal gravity (or other effects) during these encounters exposed fresh OC material on the surface (thus giving it the Q-type spectral properties). We used numerical integrations to determine the statistics of encounters of NEAs to planets. The results were used to calculate the fraction and orbital distribution of Q-type asteroids expected in the model as a function of the space weathering timescale, tsw (see main text for definition), and maximum distance, r∗, at which planetary encounters can reset the surface. We found that tsw ∼ 106 yr (at 1 AU) and r∗ ∼ 5Rpl, where Rpl is the planetary radius, best fit the data. Values tsw < 105 yr would require that r∗ > 20Rpl, which is probably implausible because these very distant encounters should be irrelevant. Also, the fraction of Q-type NEAs would be probably much larger than the one observed if tsw > 107 yr. We found that tsw ∝ q2, where q is the perihelion distance, expected if the solar wind sputtering controls tsw, provides a better match to the orbital distribution of Q-type NEAs than models with fixed tsw. We also discuss how the Earth magnetosphere and radiation effects such as YORP can influence the spectral properties of NEAs. 相似文献
9.
P. Pergola K. Geurts C. Casaregola M. Andrenucci 《Celestial Mechanics and Dynamical Astronomy》2009,105(1-3):19-32
Application of low thrust propulsion to interconnect ballistic trajectories on invariant manifolds associated with multiple circular restricted three body systems has been investigated. Sun-planet three body models have been coupled to compute the two ballistic trajectories, where electric propulsion is used to interconnect these trajectories as no direct intersection in the Poincarè sections exists. The ability of a low thrust to provide the energy change required to transit the spacecraft between two systems has been assessed for some Earth to Mars transfers. The approach followed consists in a planetary escape on the unstable manifold starting from a periodic orbit around one of the two collinear libration points near the secondary body. Following the planetary escape and the subsequent coasting phase, the electric thruster is activated and executes an ad-hoc thrusting phase. The complete transfer design, composed of the three discussed phases, and possible applications to Earth–Mars missions is developed where the results are outlined in this paper. 相似文献
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Kathrin A. Hochmuth Franz V. Feilitzsch Teresa Marrodán Undagoitia Lothar Oberauer Walter Potzel Michael Wurm Brian D. Fields 《Earth, Moon, and Planets》2006,99(1-4):253-264
A future large-volume liquid scintillator detector such as the proposed 50 kton LENA (Low Energy Neutrino Astronomy) detector
would provide a high-statistics measurement of terrestrial antineutrinos originating from β-decays of the uranium and thorium
chains. Additionally, the neutron is scattered in the forward direction in the detection reaction . Henceforth, we investigate to what extent LENA can distinguish between certain geophysical models on the basis of the angular
dependence of the geoneutrino flux. Our analysis is based on a Monte-Carlo simulation with different levels of light yield,
considering an unloaded PXE scintillator. We find that LENA is able to detect deviations from isotropy of the geoneutrino
flux with high significance. However, if only the directional information is used, the time required to distinguish between
different geophysical models is of the order of severals decades. Nonetheless, a high-statistics measurement of the total
geoneutrino flux and its spectrum still provides an extremely useful glance at the Earth’s interior. 相似文献
11.
Juan Getino José M. Farto José M. Ferrándiz 《Celestial Mechanics and Dynamical Astronomy》1998,71(2):95-108
In this paper, the mathematical algorithm elaborated by González, Getino and Farto (1998) is applied to four different nonrigid Earth models, in order to obtain the analytical expressions of the corresponding free frequencies. The solutions are studied, and the contributions of the different considered effects are evaluated. A numerical integration is also carried out, showing the validity of the obtained analytical solutions. 相似文献
12.
S. K. El-Labany H. N. Abd El-Razek G. A. El-Gamish 《Astrophysics and Space Science》2014,353(2):413-416
The self-similar expansion method is applied on the fluid system of equations which describes a plasma system consisting of opposite polarity dust grains, positive ions and electrons. The resultant system of equations is solved numerically to study the properties of the plasma expansion of this system. It is found that the presence of the second species of the dust has a great effect on the properties of the expansion of the other species. 相似文献
13.
In this paper we consider the translational–rotational motion of a spheroid satellite in the gravitational field, taking into account the asphericity of the earth. The harmonic coefficients of the earth’s gravitational field are taken up to J 4. The equations of motion are obtained in terms of the canonical elements of Delaunay-Andoyer. A first order solution is obtained using the perturbing technique of Lie series. 相似文献
14.
V. S. Gubanov 《Astronomy Letters》2009,35(4):270-277
The Earth’s rotation is accompanied by free circadian oscillations of its liquid core in the inner cavity of the lower mantle, which perturb the angular momentum of the entire Earth and produce an additional free nutation of the celestial pole called free core nutation (FCN). Since this nutation causes resonances in the diurnal tides and in the expansions of luni—solar nutation, its study, especially an improvement of the FCN period, is of fundamental importance for the theory of the Earth’s rotation. We have determined the FCN parameters from a joint analysis of equidistant series of coordinates of the celestial pole obtained from the combined processing of VLBI observations on global networks of stations for the interval 1984.0–2008.4 by IERS (International Earth Rotation and Reference System Service, Paris, France) and NEOS (National Earth Orientation Service, Washington, USA). Applying a moving least-squares filter (MLSF) to these data has shown that the FCN period averaged over this time interval differs significantly from the theoretical one and its phase varies over a wide range. Using the mean quadratic collocation (MQC) method, we have obtained a new, more accurate stochastic FCN model. Its analysis by the envelope method has revealed long-term linear phase trends, calling into question not only the adopted FCN period but also its stability and, hence, the stability of the resonant effects in the Earth’s luni—solar nutation. 相似文献
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The presence of methane on Mars is of great interest, since one possibility for its origin is that it derives from living microbes. However, CH4 in the martian atmosphere also could be attributable to geologic emissions released through pathways similar to those occurring on Earth. Using recent data on methane degassing of the Earth, we have estimated the relative terrestrial contributions of fossil geologic methane vs. modern methane from living methanogens, and have examined the significance that various geologic sources might have for Mars.Geologic degassing includes microbial methane (produced by ancient methanogens), thermogenic methane (from maturation of sedimentary organic matter), and subordinately geothermal and volcanic methane (mainly produced abiogenically). Our analysis suggests that ～80% of the “natural” emission to the terrestrial atmosphere originates from modern microbial activity and ～20% originates from geologic degassing, for a total CH4 emission of ～28.0×107 tonnes year?1.Estimates of methane emission on Mars range from 12.6×101 to 57.0×104 tonnes year?1 and are 3–6 orders of magnitude lower than that estimated for Earth. Nevertheless, the recently detected martian, Northern-Summer-2003 CH4 plume could be compared with methane expulsion from large mud volcanoes or from the integrated emission of a few hundred gas seeps, such as many of those located in Europe, USA, Mid-East or Asia. Methane could also be released by diffuse microseepage from martian soil, even if macro-seeps or mud volcanoes were lacking or inactive. We calculated that a weak microseepage spread over a few tens of km2, as frequently occurs on Earth, may be sufficient to generate the lower estimate of methane emission in the martian atmosphere.At least 65% of Earth’s degassing is provided by kerogen thermogenesis. A similar process may exist on Mars, where kerogen might include abiogenic organics (delivered by meteorites and comets) and remnants of possible, past martian life. The remainder of terrestrial degassed methane is attributed to fossil microbial gas (～25%) and geothermal-volcanic emissions (～10%). Global abiogenic emissions from serpentinization are negligible on Earth, but, on Mars, individual seeps from serpentinization could be significant. Gas discharge from clathrate-permafrost destabilization should also be considered.Finally, we have shown examples of potential degassing pathways on Mars, including mud volcano-like structures, fault and fracture systems, and major volcanic edifices. All these types of structures could provide avenues for extensive gas expulsion, as on Earth. Future investigations of martian methane should be focused on such potential pathways. 相似文献
17.
Some asteroids in Earth‐crossing orbits avoid close approaches by entering in a mean motion resonance whenever the distance between the two orbits is small. These orbits are ‘Toro class’ according to the classification of (Milani et al., 1989). This protection mechanism can be understood by a semi‐averaged model, in which the fast variables are removed and the dynamical variables are the critical argument and the semimajor axis, with dependence upon a slow parameter. The adiabatic invariant theory can be applied to this model and accounts for all the qualitative features of the orbits in this class, including the onset of the libration when the orbit distance is small. Because of the neglected perturbations by the other planets, this theory is approximate and the adiabatic invariant is conserved only with low accuracy moreover, the Toro state can be terminated by a close approach to another planet (typically Venus). “Would you tell me, please, which way I ought to go from here?” “That depends a good deal on where you want to get to,” said the Cat. Alice in Wonderland, L. Carroll 相似文献
18.
The Earth–Moon L1 libration point is proposed as a human gateway for space transportation system of the future. This paper
studies indirect transfer using the perturbed stable manifold and lunar flyby to the Earth–Moon L1 libration point. Although
traditional studies indicate that indirect transfer to the Earth–Moon L1 libration point does not save much fuel, this study
shows that energy efficient indirect transfer using the perturbed stable manifold and lunar flyby could be constructed in
an elegant way. The design process is given to construct indirect transfer to the Earth–Moon L1 libration point. Simulation
results show that indirect transfer to the Earth–Moon L1 libration point saves about 420 m/s maneuver velocity compared to
direct transfer, although the flight time is about 20 days longer. 相似文献
19.
A reference catalogue of 373 well-defined high-speed plasma streams identified in the solar wind measurements from 1985 to 1996 is reported. The data base for this study is the interplanetary plasma/magnetic field data compilation made available by the NSSDC/WDC-A for rockets and satellites (NASA/GSFC-Greenbelt). The main characteristics of those streams, such as the beginning time, the duration, the origin of them (corotating or flare-generated), the interplanetary magnetic field polarity (Stanford magnetic field), are given in the catalogue.The long-term variation in the occurrence rate of high-speed streams shows interesting differences between even and odd solar cycles when catalogues for solar cycles 20, 21, and 22 are considered together. Hence, this catalogue, extended now over three solar cycles, should be useful for studies connected with solar-interplanetary or solar-terrestrial phenomena, and to clarify solar activity in time. 相似文献
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Vaduvescu O. Aznar Macias A. Wilson T. G. Zegmott T. Pérez Toledo F. M. Predatu M. Gherase R. Pinter V. Pozo Nunez F. Ulaczyk K. Soszyński I. Mróz P. Wrona M. Iwanek P. Szymanski M. Udalski A. Char F. Salas Olave H. Aravena-Rojas G. Vergara A. C. Saez C. Unda-Sanzana E. Alcalde B. de Burgos A. Nespral D. Galera-Rosillo R. Amos N. J. Hibbert J. López-Comazzi A. Oey J. Serra-Ricart M. Licandro J. Popescu M. 《Earth, Moon, and Planets》2022,126(2):1-26
Earth, Moon, and Planets - The Perseverance rover (Mars 2020) mission, the first step in NASA’s Mars Sample Return (MSR) program, will select samples for caching based on their potential to... 相似文献