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41.
An Implementation of the Logarithmic Hamiltonian Method for Artificial Satellite Orbit Determination
Seppo Mikkola Phil Palmer Yoshi Hashida 《Celestial Mechanics and Dynamical Astronomy》2002,82(4):391-411
We discuss the use of a recently discovered exact two-body leapfrog for accurate symplectic integration of perturbed two-body motion and for the computation of the state-transition matrix. We pay special attention to artificial satellite orbit determination and describe in detail the evaluation of the perturbing acceleration. Inclusion of air drag and other non-canonical forces are also discussed. The main advantage of this new formulation is conceptual simplicity, for easy programming and high accuracy for orbits with large eccentricity. The method has been evaluated in real artificial satellite orbit determinations.This revised version was published online in October 2005 with corrections to the Cover Date. 相似文献
42.
We analyze the orbital behavior of four new co-orbital NEOs and the Earth horseshoe object 2002 AA29. The new objects are 2001 CK32, a 3753 Cruithne-like co-orbital of Venus, 2001 GO2 and 2003 YN107, two objects with motion similar to 2002 AA29. 2001 CK32 is on a compound orbit. The asteroid reverses its path when the mean longitude difference is −50°. Its motion is chaotic. 2001 GO2 is an Earth HS orbiter with repeated transitions to the QS phase, the next occurring 200 years from now. The HS libration period is 190 years and the QS phases last 45 years. For 2002 AA29, our simulations permit us to find useful theoretical insights into the HS-QS transitions. Its orbit can be simulated with adequate accuracy for 4400 years into the future and 1483 years into the past. The new co-orbital 2003 YN107 is at present an Earth QS. It has entered this phase in 1997 and will leave it again in 2006, completing one QS cycle. Like 2002 AA29, it has frequent transitions between HS and QS. One HS cycle takes 133 years. 相似文献
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We present a new method for fast numerical integration of close binaries inN-body systems. The basic idea is to slow down the motion of the binary artificially, which makes a faster numerical integration possible but still maintains correct treatment of secular and long-period effects on the motion. We discuss the general principle, with application to close binaries inN-body codes and in the chain regularization. 相似文献
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We consider the motions of particles in the one-dimensional Newtonian three-body problem as a function of initial values.
Using a mapping of orbits to symbol sequences we locate the initial values leading to triple collisions. These turn out to
form curves which give clear structure to the region in which the motions depend sensitively on initial conditions. In addition
to finding the triple collision orbits we also locate orbits which end up to a triple collision in both directions of time,
that is, orbits which are finite both in space and time.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
47.
We assessed in absolute and relative terms how solar radiation and water vapour pressure deficit control the latent heat flux density in a Scots pine (Pinus sylvestris L.) forest growing under boreal conditions. The absolute and relative total control can be expressed as sums of the physical and biological forms of control. Physical control is based on the direct effects of solar radiation and water vapour pressure deficit on latent heat flux density, and biological control on the effects of solar radiation and water vapour pressure deficit on latent heat flux density through surface resistance. Measurements based on the eddy covariance method were used in the assessment, which defined the scale adopted in the study. Relative physical control over latent heat flux density was mainly exercised by water vapour pressure deficit, and the role of solar radiation was only marginal. The relative biological control exercised by solar radiation over latent heat flux density was higher in the morning and afternoon, unlike the control exercised by water vapour pressure deficit, which was strongest around noon. The values for the relative total control exercised by solar radiation over latent heat flux density were in general higher than those for relative total control exercised by water vapour pressure deficit. This is inconsistent with expectations based on Omega theory, where a decoupling coefficient () indicates the relative control exercised by surface resistance over latent heat flux density. Solar radiation and water vapour pressure deficit do not necessarily act in opposite directions in the absolute or relative total control that they maintain over latent heat flux density. 相似文献
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Jüri Plado Lauri J. Pesonen Seppo Elo Vino Puura Kalle Suuroja 《Meteoritics & planetary science》1996,31(2):289-298
Abstract— The 4 km wide and 500 m deep circular Kärdla impact structure in Hiiumaa Island, Estonia, of middle Ordovician age (～455 Ma), is buried under Upper Ordovician and Quaternary sediments. To constrain the geophysical models of the structure, petrophysical properties such as magnetic susceptibility, natural remanent magnetization (NRM), density, electrical conductivity, porosity and P-wave velocity were measured on samples of crystalline and sedimentary rocks collected from drill cores in different parts of the structure and the surrounding area. The results were used to interpret the central gravity anomaly of ?3 mGal and the magnetic anomaly of ?100 nT and also the surrounding weak positive anomalies revealed by high precision survey data. The unshocked granitic rocks outside the structure have a mean density of ～2630 kgm?3. Their shocked counterparts have densities of ～2400 kgm?3 at a depth of ～500 m, increasing up to 2550 kgm?3 at a depth of 850 m. Porosity and electrical conductivity decrease, but P-wave velocity increases as density increases away from the impact point. Thus, the gradual changes in the physical properties of the rocks as a function of radial distance from the crater centre are consistent with an impact origin for Kärdla. As in many other impact structures, the magnetization of the shocked rocks are also clearly lower than those of unshocked target rocks. A new geophysical and geological model of the Kärdla structure is presented based on geophysical field measurements and data on gradual changes in petrophysical parameters of the shocked target and overlying rocks, together with structural data from numerous boreholes. An important feature of this model is the lack of an observable geophysical signature of the central uplift observed in drillcores. 相似文献
50.
Seppo Mikkola 《Celestial Mechanics and Dynamical Astronomy》1997,68(1):87-104
The use of regularization methods based on the Kustaanheimo-Stiefel transformation (KS) is reviewed. The history of the development
of such methods is summarized and anecdotal information about the related events is told. Details of the multi-particle regularization
methods are given, including the most recent developments.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献