The Experts below are selected from a list of 114 Experts worldwide ranked by ideXlab platform
Peter A. Robinson - One of the best experts on this subject based on the ideXlab platform.
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Local transit‐time damping in a magnetic field, and the arrest of lower‐hybrid wave collapse
Physics of Plasmas, 1996Co-Authors: Andrew Melatos, Peter A. RobinsonAbstract:The transit‐time power dissipated locally within a coherent wave packet in the presence of ambient and induced magnetic fields is calculated analytically as a function of position via a Perturbed‐Orbit approach, generalizing earlier results for unmagnetized interactions. The theory is used to investigate local damping in a nonlinearly‐collapsing lower‐hybrid (LH) wave packet, and hence to estimate the arrest scale of LH wave collapse in a thermal electron‐ion plasma. It is shown that either electrons or ions can dominate damping, depending on the strength of the magnetic field and the electron and ion temperatures.
V. A. Shefer - One of the best experts on this subject based on the ideXlab platform.
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Determination of an Intermediate Perturbed Orbit using Multiple Observations
Proceedings of the International Astronomical Union, 2014Co-Authors: V. A. SheferAbstract:Two methods are briefly stated for finding the preliminary Orbit of a small celestial body from its three or more pairs of angular measurements and the corresponding time instants. The methods are based on using the approach that we previously developed for constructing the intermediate Orbit from a minimum number of observations. This intermediate Orbit allows for most of the perturbations in the motion of the body under study. The methods proposed use the Herget's algorithmic scheme that makes it possible to involve additional observations as well. Using the determination of Orbits of some asteroids as examples, we compare the results obtained by applying the Herget multiple-observation algorithm and the proposed methods. The comparison shows that the proposed methods are an efficient means for studying Perturbed motion. They are especially advantageous if applied to high-precision observational data covering short Orbital arcs.
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calculation of the intermediate Perturbed Orbit from three or more positions of a small body on the celestial sphere
Solar System Research, 2013Co-Authors: V. A. SheferAbstract:Two new methods are described for finding the Orbit of a small celestial body from three or more pairs of angular measurements and the corresponding time points. The methods are based on, first, the approach that has been developed previously by the author to the determination, from a minimum number of observations, of intermediate Orbit considering most of the perturbations in the bodies’ motion and, second, Herget’s algorithmic procedure enabling the introduction of additional observations. The errors of Orbital parameters calculated by the proposed methods are two orders of magnitude smaller than the corresponding errors of the traditional approach based on the construction of an unPerturbed Keplerian Orbit. The thus-calculated Orbits of the minor planets 1566 Icarus, 2002 EC1, and 2010 TO48 are used to compare the results of Herget’s multiposition procedure and the new methods. The comparison shows that the new methods are highly effective in the study of Perturbed motion. They are particularly beneficial if high-precision observational data covering short Orbital arcs are available.
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Determination of an intermediate Perturbed Orbit from three position vectors
Astronomy Letters, 2007Co-Authors: V. A. SheferAbstract:We suggest a new approach to solving the problem of finding the Orbit of a celestial body from its three spatial position vectors and the corresponding times. It allows most of the perturbations in the motion of a celestial body to be taken into account. The approach is based on the theory of intermediate Orbits that we developed previously. We construct the Orbit the motion along which is a combination of two motions: the motion of a fictitious attracting center whose mass varies according to Mestschersky’s first law and the motion relative to the fictitious center. The first motion is generally parabolic, while the second motion is described by the equations of the Gylden-Mestschersky problem. The constructed Orbit has such parameters that their limiting values at any reference epoch define a superosculating intermediate Orbit with a fourth-order tangency. We have performed a numerical analysis to estimate the accuracy of approximating the Perturbed motion of two minor planets, 145 Adeona and 4179 Toutatis, by the Orbits computed using two-position procedures (the classical Gauss method and the method that we suggested previously), a three-position procedure based on the Herrick-Gibbs equation, and the new method. Comparison of the results obtained suggests that the latter method has an advantage.
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The Determination of an Intermediate Perturbed Orbit from Two Position Vectors
Solar System Research, 2003Co-Authors: V. A. SheferAbstract:Based on the theory of intermediate Orbits developed earlier by the author of this paper, a new approach is proposed to the solution of the problem of finding the Orbit of a celestial body with the use of two position vectors of this body and the corresponding time interval. This approach makes it possible to take into account the main part of perturbations. The Orbit is constructed, the motion along which is a combination of two motions: the uniform motion along a straight line of a fictitious attracting center, whose mass varies according to the first Meshchersky law, and the motion around this center. The latter is described by the equations of the Gylden–Meshchersky problem. The parameters of the constructed Orbit are chosen so that their limiting values at any reference epoch determine a superosculating intermediate Orbit with third-order tangency. The accuracy of approximation of the Perturbed motion by the Orbits calculated by the classical Gauss method and the new method is illustrated by an example of the motion of the unusual minor planet 1566 Icarus. Comparison of the results obtained shows that the new method has obvious advantages over the Gauss method. These advantages are especially prominent in cases where the angular distances between the reference positions are small.
Andrew Melatos - One of the best experts on this subject based on the ideXlab platform.
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Local transit‐time damping in a magnetic field, and the arrest of lower‐hybrid wave collapse
Physics of Plasmas, 1996Co-Authors: Andrew Melatos, Peter A. RobinsonAbstract:The transit‐time power dissipated locally within a coherent wave packet in the presence of ambient and induced magnetic fields is calculated analytically as a function of position via a Perturbed‐Orbit approach, generalizing earlier results for unmagnetized interactions. The theory is used to investigate local damping in a nonlinearly‐collapsing lower‐hybrid (LH) wave packet, and hence to estimate the arrest scale of LH wave collapse in a thermal electron‐ion plasma. It is shown that either electrons or ions can dominate damping, depending on the strength of the magnetic field and the electron and ion temperatures.
Changzhu Wei - One of the best experts on this subject based on the ideXlab platform.
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linearized dynamics model for relative motion under a j2 Perturbed elliptical reference Orbit
International Journal of Non-linear Mechanics, 2013Co-Authors: Changzhu Wei, Sangyoung Park, Chandeok ParkAbstract:Abstract A method for directly establishing a linearized dynamics model of relative motion for a satellite formation flying on an arbitrary elliptical reference Orbit is presented. The proposed linearized dynamics model of relative motion is intuitive and favorable to be utilized for designing formation control system, implementing guidance algorithm, and analyzing optimization problems etc. An analytical solution for the radius of a reference Orbit affected by the J 2 geopotential disturbance is used to approximate the actual reference Orbit rather than directly use the unPerturbed standard Orbit. The accuracy of the analytical solution directly affects the accuracy of the linear relative motion model of a satellite formation. Thus, emphasis is placed on deducing an accurate analytical solution for a Perturbed reference Orbit radius, which is analyzed by adding Perturbed motion in the radial direction to the corresponding unPerturbed reference Orbit radius. Furthermore, by considering time - varying angular velocity of an elliptical reference Orbit, the analytical solution of a Perturbed Orbit radius is obtained in the true anomaly domain. In order to better match the actual force conditions of a satellite formation, a Perturbed true anomaly and Perturbed argument of perigee are adopted and substituted into the gradient of the J 2 disturbance force. Simulation results indicate the analytical solution for the radius of a Perturbed elliptical reference Orbit is accurate, and the proposed linear dynamics model of relative motion can track the high - fidelity simulated relative motion more accurately than previously proposed dynamics models, even for an elliptical reference Orbit with high eccentricity.
Chandeok Park - One of the best experts on this subject based on the ideXlab platform.
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linearized dynamics model for relative motion under a j2 Perturbed elliptical reference Orbit
International Journal of Non-linear Mechanics, 2013Co-Authors: Changzhu Wei, Sangyoung Park, Chandeok ParkAbstract:Abstract A method for directly establishing a linearized dynamics model of relative motion for a satellite formation flying on an arbitrary elliptical reference Orbit is presented. The proposed linearized dynamics model of relative motion is intuitive and favorable to be utilized for designing formation control system, implementing guidance algorithm, and analyzing optimization problems etc. An analytical solution for the radius of a reference Orbit affected by the J 2 geopotential disturbance is used to approximate the actual reference Orbit rather than directly use the unPerturbed standard Orbit. The accuracy of the analytical solution directly affects the accuracy of the linear relative motion model of a satellite formation. Thus, emphasis is placed on deducing an accurate analytical solution for a Perturbed reference Orbit radius, which is analyzed by adding Perturbed motion in the radial direction to the corresponding unPerturbed reference Orbit radius. Furthermore, by considering time - varying angular velocity of an elliptical reference Orbit, the analytical solution of a Perturbed Orbit radius is obtained in the true anomaly domain. In order to better match the actual force conditions of a satellite formation, a Perturbed true anomaly and Perturbed argument of perigee are adopted and substituted into the gradient of the J 2 disturbance force. Simulation results indicate the analytical solution for the radius of a Perturbed elliptical reference Orbit is accurate, and the proposed linear dynamics model of relative motion can track the high - fidelity simulated relative motion more accurately than previously proposed dynamics models, even for an elliptical reference Orbit with high eccentricity.