scholarly journals Nongravitational effects and the LAGEOS eccentricity excitations

1997 ◽  
Vol 102 (B2) ◽  
pp. 2711-2729 ◽  
Author(s):  
Gilles Métris ◽  
David Vokrouhlický ◽  
John C. Ries ◽  
Richard J. Eanes
Keyword(s):  
Nongravitational Effects

Models of comets with strongly variable nongravitational effects

1999 ◽  
Vol 173 ◽  
pp. 381-387
Author(s):  
M. Królikowska ◽  
G. Sitarski ◽  
S. Szutowicz
Keyword(s):  
Cometary Nucleus ◽  
Spin Axis ◽  
Reactive Force ◽  
Orbital Elements ◽  
Cometary Nuclei ◽  
Short Period ◽  
Basic Parameters ◽  
Polar Radius ◽  
Cometary Activity ◽  
Nongravitational Effects

AbstractThe nongravitational motion of five “erratic” short-period comets is studied on the basis of published astrometric observations. We present the precession models which successfully link all the observed apparitions of the comets: 21P/Giacobini-Zinner, 31P/Schwassmann-Wachmann 2, 32P/Comas Solá, 37P/Forbes, and 43P/Wolf-Harrington. We used the Sekanina's forced precession model of the rotating cometary nucleus to include the nongravitational terms into equations of the comet's motion. Values of six basic parameters (four connected with the rotating comet nucleus and two describing the precession of spin-axis of the nucleus) have been determined along the orbital elements from positional observations of the comets. The solutions were derived with additional assumptions which introduce instantaneous changes of modulus of reactive force,Aand of maximum of cometary activity with respect to perihelion time. The present precession models impose some contraints on sizes and rotational periods of cometary nuclei. According to our solutions the nucleus of 21P/Giacobini-Zinner with oblateness along the spin-axis of about 0.32 (equatorial to polar radius of 1.46) is the most oblate among five investigated comets.

A Method of Integrating the Equations of Motion in Special Coordinates and the Elimination of a Discontinuity in the Theory of the Motion of Periodic Comet Wolf

1972 ◽  
Vol 45 ◽  
pp. 95-102
Author(s):  
E. I. Kazimirchak-Polonskaya
Keyword(s):  
Differential Equations ◽  
Electronic Computer ◽  
Equations Of Motion ◽  
Close Approach ◽  
Time Interval ◽  
Variable Step ◽  
Rectangular Coordinates ◽  
Periodic Comet ◽  
Nongravitational Effects

From the integration formulae of Numerov and Subbotin we have developed and programmed for an electronic computer a particular method for integrating the differential equations of cometary motion in special rectangular coordinates, with a variable step and allowing for all planetary perturbations and nongravitational effects over a time interval of 400 yr. Application of this method and our set of programmes to the investigation of the motion of P/Wolf permits us to eliminate the discontinuity that has hitherto existed in the theory on account of the comet's close approach to Jupiter in 1922.

scholarly journals A Library of Standard Programmes for Constructing Numerical Theories for Studying the Motion and Evolution of the Orbits of the Minor Bodies of the Solar System

1972 ◽  
Vol 45 ◽  
pp. 86-89 ◽  
Author(s):  
N. A. Bokhan
Keyword(s):  
Solar System ◽  
Variable Step ◽  
Rectangular Coordinates ◽  
Lagrangian Interpolation ◽  
Orbit Improvement ◽  
Nongravitational Effects

At the Institute for Theoretical Astronomy we have formed a library containing about 120 standard computer programmes. They include calculation of rectangular coordinates and velocities from elements, Lagrangian interpolation, and orbit improvement by the Eckert-Brouwer method. For the investigation of the motions of the minor bodies of the solar system we have constructed a programme for integration with a variable step and making allowance for perturbations by all the major planets and for nongravitational effects. The calculation of the perturbations is carried out using Herrick's vector parameters by the method of variation of arbitrary constants. The programme has been used for studying the motion of P/Encke.

scholarly journals 8. Comet Halley and Nongravitational Forces

1977 ◽  
Vol 39 ◽  
pp. 61-64
Author(s):  
D. K. Yeomans
Keyword(s):  
Force Model ◽  
Water Ice ◽  
Comet Halley ◽  
Nongravitational Effects ◽  
Nongravitational Forces

The motion of Comet Halley is investigated over the 1607-1911 interval. The required nongravitational force model was found to be most consistent with a rocket-type thrust from the vaporization of water-ice in the comet’s nucleus. The nongravitational effects are time-independent over the investigated interval.

scholarly journals Nongravitational Effects on Comets: the Current Status

1972 ◽  
Vol 45 ◽  
pp. 135-143
Author(s):  
B. G. Marsden
Keyword(s):  
Heliocentric Distance ◽  
Equations Of Motion ◽  
Current Status ◽  
Future Research ◽  
Secular Changes ◽  
Nongravitational Effects ◽  
Nongravitational Forces

A method for allowing for the effects of nongravitational forces on the motions of comets is summarized. Study of the motions of specific comets indicates that these forces act essentially continuously but have a high inverse dependence on heliocentric distance; there is also evidence for secular changes. The equations of motion employed are discussed in terms of the Whipple icyconglomerate model. Nongravitational parameters are tabulated for all 46 comets observed at three or more perihelion passages. We point out the particular problems that still exist for certain comets and suggest directions for future research.

scholarly journals On Nongravitational Effects in two Classes of Models for Cometary Nuclei

1972 ◽  
Vol 45 ◽  
pp. 287-293
Author(s):  
O. V. Dobrovol'skij ◽  
M. Z. Markovich
Keyword(s):  
Heliocentric Distance ◽  
Orbital Plane ◽  
Secular Change ◽  
Reactive Force ◽  
Cometary Nuclei ◽  
Ice Surface ◽  
First Case ◽  
Equation Of Heat Conduction ◽  
Change In Mean ◽  
Nongravitational Effects

Two types of cometary nuclei are considered: a homogeneous icy nucleus and an icy nucleus covered with a dispersive surface layer, 1 cm thick and having poor heat conductivity. The temperature of the evaporating ice surface of a nucleus rotating in a period of 6 hours about an axis perpendicular to the orbital plane was determined by numerical integration of the equation of heat conduction in the first case and of the Stefan problem in the second. For a nucleus of radius 105 cm and mass of 3.8 × 1015 g the reactive force was found to be about 107 dyn in either case, and the secular change in mean motion is of the order of the observed values. For the homogeneous nucleus the dependence of the reactive force on heliocentric distance is obtained.

scholarly journals The Solution of Problems of Cometary Astronomy on Electronic Computers

1972 ◽  
Vol 45 ◽  
pp. 90-94 ◽  
Author(s):  
N. A. Belyaev
Keyword(s):  
Differential Equations ◽  
Numerical Integration ◽  
Equations Of Motion ◽  
Variable Step ◽  
Electronic Computers ◽  
Nongravitational Effects

A series of standard programmes has been developed for numerical integration by Cowell's method of the differential equations of motion of minor bodies. A variable step is used, and perturbations by eight major planets and nongravitational effects are taken into consideration. Further programmes have been constructed as part of a general attempt at ITA to produce numerical theories of cometary motion. They include the reduction of observations, the comparison of the observations with theory and the improvement of orbits. The programmes make it possible to calculate (O–C) residuals of up to 2000 observations simultaneously.

scholarly journals A Numerical Analysis of the Motion of Periodic Comet Brooks 2

1972 ◽  
Vol 45 ◽  
pp. 156-166 ◽  
Author(s):  
P. Stumpff
Keyword(s):  
Numerical Analysis ◽  
Close Approach ◽  
Before And After ◽  
Osculating Elements ◽  
Periodic Comet ◽  
Nongravitational Effects

Various sets of osculating elements of P/Brooks 2, derived by Dubyago, are introduced into an N-body integration programme and run from 1686 to 1976. Attempts are made to find a system of elements which links the apparitions before and after the close approach to Jupiter in 1922. The propagation of differential perturbations, and also nongravitational effects, is examined.

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