共查询到20条相似文献，搜索用时 15 毫秒
1.
Richard A. Serafin 《Celestial Mechanics and Dynamical Astronomy》1989,47(1):37-56
In this paper we consider orbital element distributions for comets moving on admissible orbits in the Oort cloud and distributions for some functions that depend on the orbital elements. Moreover, we find the probability of an event that an arbitrarily chosen admissible orbit belongs to the set (r) of orbital elements and the distribution of circular velocities in the cloud. 相似文献
2.
K. Fujimoto J. M. Maruskin D. J. Scheeres 《Celestial Mechanics and Dynamical Astronomy》2010,106(2):157-182
Situational awareness of Earth-orbiting particles is important for human extraterrestrial activities. Given an optical observation,
an admissible region can be defined over the topocentric range/range-rate space, with each point representing a possible orbit
for the object. However, based on our understanding of Earth orbiting objects, we expect that certain orbits in that distribution,
such as circular or zero-inclination orbits, would be more likely than others. In this research, we present an analytical
approach for describing the existence of such special orbits for a given observation pass, and investigate topological features
of the range/range-rate space by means of singularities in orbital elements. 相似文献
3.
Geomagnetic storms driven by solar eruptions are known to have significant effects on the total density of the upper atmosphere
in the altitude range 250–1000 km. This in turn causes a measurable effect on the orbits of resident space objects in this
altitude range. We analyzed a sample of these orbits, both from sensor data and from orbital element sets, during the period
surrounding the 14 July 2000 solar activity. We present information concerning the effects of this event on the orbits of
resident space objects and how well accepted atmospheric models were able to represent it. As part of this analysis, we describe
a technique for extracting atmospheric density information from orbital element sets. On daily time scales, the effect of
geomagnetic activity appears to be more important than that of prompt radiation. However, the limitations in time and amplitude
quantization of the accepted solar indices are evident. A limited comparison is also made with previous solar storm events. 相似文献
4.
Saurabh Jha Guillermo Torres Robert P. Stefanik David W. Latham Tsevi Mazeh 《Monthly notices of the Royal Astronomical Society》2000,317(2):375-384
The triple-lined spectroscopic triple system HD 109648 has one of the shortest periods known for the outer orbit in a late-type triple, 120.5 d, and the ratio between the periods of the outer and the inner orbits is small, 22:1. With such extreme values, this system should show orbital element variations over a time-scale of about a decade. We have monitored the radial velocities of HD 109648 with the CfA Digital Speedometers for 8 yr, and have found evidence for modulation of some orbital elements. While we see no definite evidence for modulation of the inner binary eccentricity, we clearly observe variations in the inner and the outer longitudes of periastron, and in the radial velocity amplitudes of the three components. The observational results, combined with numerical simulations, allow us to put constraints on the orientation of the orbits. 相似文献
5.
Richard A. Serafin 《Celestial Mechanics and Dynamical Astronomy》1987,41(1-4):79-98
In this paper we deal with determinations of: admissible orbits and ranges of orbital velocity in the cloud, extremal velocities at the distance r from the Sun. Moreover, in velocity space we consider the
r
region in which there are located tips of velocity vectors for comets moving on admissible orbits. 相似文献
6.
《Planetary and Space Science》1999,47(6-7):873-881
The ROSETTA spacecraft will fly-by a few asteroids during its course to the final cometary target. The candidate asteroids presently are 3840 Ministrobel (S-type), 2703 Siwa and 140 (C-type).With the limited data presently available on these bodies we calculated some approximate quantities which may be useful to select the fly-by trajectories of the ROSETTA probe. In particular we derived the zones in which particles could stably orbit by analyzing Hills problem of three hierarchical masses—the sun, the asteroid and the orbiting particle. Then, following the approach of Hamilton and Burns, the effects of solar radiation pressure and of the ellipticity of the orbits were also taken into account. In this way for each asteroid we could calculate not only a classical quantity like the radius of the Hill sphere, but also the critical starting orbital distance (as a function of orbital inclination) within which most orbits remain bound to the asteroid, and outside which most escape as a consequence of perturbations. Moreover we determined the orbital stability zone, defined as the union of all the numerically integrated orbits showing long-term stability, for each of the target asteroids. The particular shape of these zones would suggest to have the spacecrafts close approach out of the orbital plane of the asteroids.To further investigate this problem and, in particular, to take into account the irregular shape of the asteroids, we developed a model using a polyhedral representation of the central rotating body, following a theory developed by Werner and Scheeres. This model is described here and the first orbital integration results are presented. © 1999 Elsevier Science Ltd. All rights reserved. 相似文献
7.
Generally, any initially-close satellites—chief and deputy—moving on orbits with slightly different orbital elements, will depart each other on locally unbounded relative trajectories. Thus, constraints on the initial conditions must be imposed to mitigate the chief-deputy mutual departure. In this paper, it is analytically proven that choosing the chief’s orbit to be a frozen orbit can mitigate the natural relative drift of the satellites. Using mean orbital element variations, it is proven that if the chief’s orbit is frozen, then the mean differential eccentricity is periodic, leading to a periodic variation of the differential mean argument of latitude. On the other hand, if the chief’s orbit is non-frozen, a secular growth in the differential mean argument of latitude leads to a concomitant along-track separation of the deputy from the chief, thereby considerably increasing the relative distance evolution over time. Long-term orbital simulation results indicate that the effect of choosing a frozen orbit vis-à-vis a non-frozen orbit can reduce the relative distance drift by hundreds of meters per day. 相似文献
8.
B. Abramenko 《Astrophysics and Space Science》1978,54(2):323-342
Observational evidence on the widespread occurrence of warping of the outer part of the galactic plane in many galaxies is presented and various hypotheses for its explanation are reviewed. None is found to be able to account for all the cases reported. Other phenomena considered are: (1) deviations from the galactic plane in the innermost nuclear region; (2) differences in orientation of the nucleus and disk in spiral galaxies; (3) changing ellipticity with distance from the center.After discussing the observations available, a theory has been developed which explains the phenomena mentioned as natural consequences of the non-steady nature of galactic systems due to time-dependent metric. This manifests itself in the appearance of tangential acceleration which leads necessarily to variability of the orbital plane and orbital eccentricity in dependence on the radius vector of the orbits. 相似文献
9.
Mikael Granvik Jenni Virtanen Dagmara Oszkiewicz Karri Muinonen 《Meteoritics & planetary science》2009,44(12):1853-1861
Abstract— We are making an open‐source asteroid orbit computation software package called OpenOrb publicly available. OpenOrb is built on a well‐established Bayesian inversion theory, which means that it is to a large part complementary to orbit‐computation packages currently available. In particular, OpenOrb is the first package that contains tools for rigorously estimating the uncertainties resulting from the inverse problem of computing orbital elements using scarce astrometry. In addition to the well‐known least‐squares method, OpenOrb also contains both Monte‐Carlo (MC) and Markov‐Chain MC (MCMC; Oszkiewicz et al. [2009]) versions of the statistical ranging method. Ranging allows the user to obtain sampled, non‐Gaussian orbital‐element probability‐density functions and is therefore optimized for cases where the amount of astrometry is scarce or spans a relatively short time interval. Ranging‐based methods have successfully been applied to a variety of different problems such as rigorous ephemeris prediction, orbital element distribution studies for transneptunian objects, the computation of invariant collision probabilities between near‐Earth objects and the Earth, detection of linkages between astrometric asteroid observations within an apparition as well as between apparitions, and in the rigorous analysis of the impact of orbital arc length and/or astrometric uncertainty on the uncertainty of the resulting orbits. Tools for making ephemeris predictions and for classifying objects based on their orbits are also available in OpenOrb. As an example, we use OpenOrb in the search for candidate retrograde and/or high‐inclination objects similar to 2008 KV42 in the known population of transneptunian objects that have an observational time span shorter than 30 days. 相似文献
10.
M. Xavier James Raj 《Planetary and Space Science》2009,57(1):34-41
A new non-singular analytical theory for the contraction of near-Earth satellite orbits under the influence of air drag is developed in terms of uniformly regular Kustaanheimo and Stiefel (KS) canonical elements using an oblate atmosphere with variation of density scale height with altitude. The series expansions include up to fourth power in terms of eccentricity and c (a small parameter dependent on the flattening of the atmosphere). Only two of the nine equations are solved analytically to compute the state vector and change in energy at the end of each revolution, due to symmetry in the equations of motion. It is observed that the analytically computed values of the semi-major axis and eccentricity are consistent with the numerically integrated values up to 500 revolutions over a wide range of the drag-perturbed orbital parameters. The theory can be effectively used for re-entry of near-Earth objects. 相似文献
11.
Tsuko Nakamura 《Icarus》1981,45(3):529-544
The mean orbital evolution of long-period comets for 16 representative initial orbits to short-period comets is calculated by a Monte Carlo method. First, trivariate perturbation distributions of barycentric Kepler energy, total angular momentum, and its z component in single encounters of comets with Jupiter are obtained numerically. Their characteristics are examined in detail and the distributions are found to be simple, symmetric, and easy to handle. Second, utilizing these distributions, we have done trivariate Monte Carlo simulations of the orbital evolution of long-period comets, with special emphasis on high-inclination orbits. About half of the 16 initial orbits are traced up to 5000 returns. For each of these orbits, the mean values of semimajor axis, perihelion distance, and inclination; their standard deviations, survival, and capture rates; as well as time scales of orbital evolution are calculated as functions of return number. Survival rates of the initial orbits with high inclination (～90°) and small perihelion distance (～1–2 AU) have been found to be only two or three times smaller than those of the main-source orbits of short-period comets established quantitatively by Everhart. The time scales of orbitsl evolution of the former, however, are nearly 10 times longer than the latter. There is a general trend that, for smaller perihelion distance, the survival efficiency becomes higher. The results of this paper should be considered a basis for a succeeding paper (Paper II) in which the physical lifetime of comets will be determined, and a comparison with the orbital data will be done. 相似文献
12.
Position and velocity perturbations in the orbital frame in terms of classical element perturbations
Stefano Casotto 《Celestial Mechanics and Dynamical Astronomy》1993,55(3):209-221
The transformation of classical orbit element perturbations to perturbations in position and velocity in the radial, transverse and normal directions of the orbital frame is developed. The formulation is given for the case of mean anomaly perturbations as well as for eccentric and true anomaly perturbations. Approximate formulas are also developed for the case of nearly circular orbits and compared with those found in the literature. 相似文献
13.
14.
Michael E. Hough 《Celestial Mechanics and Dynamical Astronomy》1981,25(2):137-157
The long period dynamics of Sun-synchronous orbits near the critical inclination 116.6° are investigated. It is known that, at the critical inclination, the average perigee location is unchanged by Earth oblateness. For certain values of semimajor axis and eccentricity, orbit plane precession caused by Earth oblateness is synchronous with the mean orbital motion of the apparent Sun (a Sun-synchronism). Sun-synchronous orbits have been used extensively in meteorological and remote sensing satellite missions. Gravitational perturbations arising from an aspherical Earth, the Moon, and the Sun cause long period fluctuations in the mean argument of perigee, eccentricity, inclination, and ascending node. Double resonance occurs because slow oscillations in the perigee and Sun-referenced ascending node are coupled through the solar gravity gradient. It is shown that the total number and infinitesimal stability of equilibrium solutions can change abruptly over the Sun-synchronous range of semimajor axis values (1.54 to 1.70 Earth radii). The effect of direct solar radiation pressure upon certain stable equilibria is investigated. 相似文献
15.
We investigated by numerical integrations the long-term orbital evolution of four giant comets or comet-like objects. They are Chiron, P/Schwassmann-Wachmann 1 (SW1), Hidalgo, and 1992AD (5145), and their orbits were traced for 100–200 thousand years (kyr) toward both the past and the future. For each object, 13 orbits were calculated, one for the nominal orbital elements and other 12 with slightly modified elements based on the rms residual of the orbit determination and on the number of observations. As past studies indicate, their orbital evolution is found to be very chaotic, and thus can be described only in terms of probability. Plots of the semi-major axis (a) and perihelion distance (q) of the objects treated here seem to cross each other frequently, suggesting a possibility of their common evolutionary paths. About a half of all the calculated orbits showedq- ora-decreasing evolution. This indicates that, at least on the time scale in question, the giant comet-like objects are possibly on a dynamical track that can lead to capture from the outer solar system. We could hardly find the orbits with perihelia far outside the orbit of Saturn (q>15 AU). This is perhaps because the evolution of the orbits beyond Saturn is so slow that substantial orbital changes do not take place within 100–200 kyr. 相似文献
16.
Jeannette Heiligers Colin R. McInnes 《Celestial Mechanics and Dynamical Astronomy》2014,120(2):163-194
This paper introduces new families of Sun-centered non-Keplerian orbits (NKOs) that are constrained to a three-dimensional, cylindrical or spherical surface. As such, they are an extension to the well-known families of displaced NKOs that are confined to a two-dimensional plane. The cylindrical and spherical orbits are found by investigating the geometrically constrained spacecraft dynamics. By imposing further constraints on the orbit’s angular velocity and propulsive acceleration, the set of feasible orbits is defined. Additionally, the phase spaces of the orbits are explored and a numerical analysis is developed to find periodic orbits. The richness of the problem is further enhanced by considering both an inverse square acceleration law (mimicking solar electric propulsion) and a solar sail acceleration law to maintain the spacecraft on the three-dimensional surface. The wealth of orbits that these new families of NKOs generate allows for a range of novel space applications. 相似文献
17.
Single close encounters between Jupiter and about 3000 hypothetical minor bodies, initially on elliptical orbits, have been studied computing the evolution of the three-body system Sun-Jupiter-object, by means of a new numerical method of integration. The fictitious population processed contains almost all the orbits which allow a close approach to the planet. The efficiency of a single encounter in varying the orbital parameters of the objects resulted to be generally poor, as it is shown by the distributions of the orbital parameter variations. Collisions and ejections from the solar system on hyperbolic orbits are little numerous; some temporary satellite capture have been recognised. The results of this work show that any attempt to study the close encounter event by means of two distinct two-body problems is physically meaningless because the mid-range perturbations, disregarded in such cases, are very far from being negligible. 相似文献
18.
Alton P. Mayo 《Celestial Mechanics and Dynamical Astronomy》1979,19(4):317-333
Analytic expressions are derived for the perturbation of planetary orbits due to a thick constant density asteroid belt. The derivations include extensions and adaptations of Plakhov's analytic expressions for the perturbations in five of the orbital elements for closed orbits around Saturn's rings. The equations of Plakhov are modified to include the effect of ring thickness and additional equations are derived for the perturbations in the sixth orbital element, the mean anomaly. The gravitational potential and orbital perturbations are derived for the asteroid belt with and without thickness, and for a hoop approximation to the belt. The procedures are also applicable to Saturn's rings and the newly discovered rings of Uranus.The effects of the asteroid belt thickness on the gravitational potential coefficients and the orbital motions are demonstrated. Comparisons between the Mars orbital perturbations obtained using the analytic expressions and those obtained using numerical integration are discussed. The effects of the asteroid belt on the Earth based ranging to Mars are also demonstrated. 相似文献
19.
A two-point boundary value problem of the Kepler orbit similar to Lambert’s problem is proposed. The problem is to find a
Kepler orbit that will travel through the initial and final points in a specified flight time given the radial distances of
the two points and the flight-direction angle at the initial point. The Kepler orbits that meet the geometric constraints
are parameterized via the universal variable z introduced by Bate. The formula for flight time of the orbits is derived. The admissible interval of the universal variable
and the variation pattern of the flight time are explored intensively. A numerical iteration algorithm based on the analytical
results is presented to solve the problem. A large number of randomly generated examples are used to test the reliability
and efficiency of the algorithm. 相似文献
20.
Using statistical orbital ranging, we systematically study the orbit computation problem for transneptunian objects (TNOs). We have automated orbit computation for large numbers of objects, and, more importantly, we are able to obtain orbits even for the most sparsely observed objects (observational arcs of a few days). For such objects, the resulting orbit distributions include a large number of high-eccentricity orbits, in which TNOs can be perturbed by close encounters with Neptune. The stability of bodies on the computed orbits has therefore been ascertained by performing a study of close encounters with the major planets. We classify TNO orbit distributions statistically, and we study the evolution of their ephemeris uncertainties. We find that the orbital element distributions for the most numerous single-apparition TNOs do not support the existence of a postulated sharp edge to the belt beyond 50 AU. The technique of statistical ranging provides ephemeris predictions more generally than previously possible also for poorly observed TNOs. 相似文献