Wyniki wyszukiwania - BazTech

1

A Semi - Analytic First Order Jupiter - Saturn Planetary Theory Part I : Outline

Kamel O. M.

Mechanics and Mechanical Engineering

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2015

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Vol. 19, nr 1

17--22

EN

Herein we lay the broad lines for the construction of a first order w.r.t planetary masses Jupiter-Saturn theory - giving the orbital elements of the two planets at any epoch. This is implemented by the evaluation of the R. H. S. of the original first order Hamiltonian equations of motion. The first order Hamiltonian is composed of the first order secular terms and the first order periodic terms. We restrict the periodic terms to be the commensurate ones for the J-S (Jupiter-Saturn) subsystem. We give throughout the text an idea to the extension of the theory to the case of the four major outer planets J-S-U-N.

2

GOCE satellite orbit in the aspect of selected gravitational perturbations

Bobojć A., Drożyner A.

Acta Geophysica

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2011

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Vol. 59, no. 2

428-452

EN

In this work, the GOCE satellite orbit is described in the aspect of perturbations in the Keplerian osculating elements. The perturbations come from the Earth and ocean tides, the gravitation of the Moon, the gravitation of the Sun, the gravitation of planets and Pluto, and the relativity effects. These perturbations are computed for the 30-day interval with a sampling of 2 min. To obtain the simulated orbit, the Cowell numerical integration method of 8th order is used. The first part of the work contains the root mean square (RMS) values of aforementioned perturbations due to the specified forces. The perturbations were compared taking into account their RMS characteristics. Perturbations in elements of the GOCE osculating orbit are also presented on the plots for successive epochs of the 30-day interval. Changes of the obtained perturbations were described and their characteristic periodic components were distinguished.

3

Selected Accelerations and Orbital Elements of the GOCE Satellite in the Time Domain

Bobojć A.

Technical Sciences / University of Warmia and Mazury in Olsztyn

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2009

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nr 12

104-117

EN

The work contains the results of the GOCE satellite orbit simulation. The GOCE satellite orbit was presented in the aspect of the temporary changes in selected accelerations and in selected keplerian elements. The satellite accelerations due to: the geopotential, the Earth tides and the ocean tides (the radial component for both), the gravitation of the Moon and the gravitation of the Sun, were presented in function of time. The showed changes in orbital elements include the semi-major axis, eccentricity, inclination, argument of perigee and right ascension of ascending node. For the orbit determination the Cowell numerical integration method of the eighth order was used. The geopotential was described by means of the EGM96 model. The mentioned temporary changes in the selected accelerations and orbital elements were described. Most of them contain the characteristic periodic components, which are close to the satellite orbital period, the Earth's rotation period and the Moon's synodic period.

PL

Praca zawiera wyniki symulacji orbity satelity GOCE. Orbitę satelity GOCE przedstawiono w aspekcie zmian czasowych wybranych przyśpieszeń i elementów keplerowskich. Przyśpieszenia satelity spowodowane przez: geopotencjał, pływy skorupy, pływy oceaniczne (składowa radialna dla obu), grawitację Słońca i grawitację Księżyca, przedstawiono w funkcji czasu. Pokazane zmiany w elementach orbity obejmują półoś wielką, mimośród, nachylenie, argument perygeum i rektascensję węzła wstępującego. Do wyznaczenia orbity użyto całkowania numerycznego metodą Cowella ósmego rzędu. Geopotencjał opisano modelem EGM96. Opisano wspomniane zmiany czasowe wybranych przyśpieszeń i elementów orbity. Większość z nich zawiera charakterystyczne składowe okresowe, które są zbliżone do okresu orbitalnego satelity, okresu rotacji Ziemi oraz okresu synodycznego Księżyca.

4

Spectral analysis of the selected accelerations and orbital elements for the GOCE satellite orbit

Bobojć A.

Artificial Satellites : Journal of Planetary Geodesy

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2008

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Vol. 43, No. 3

109--127

EN

The work contains the results of research of the simulated GOCE satellite orbit. For the 30-day orbit determination the Cowell numerical integration of the eighth order was used and the geopotential was described by means of the EGM96 model. The selected accelerations and the Keplerian elements were computed along this orbit. These accelerations included the satellite accelerations due to: the geopotential, the Earth tides and the ocean tides (the radial component for both), the gravitation of the Moon, the gravitation of the Sun, the gravitation of the Venus and the relativity effects. The computed accelerations and Keplerian elements were treated as the input data for the DFT algorithm (Discrete Fourier Transform) to determine their spectral characteristics, i.e. the amplitude power spectral densities (PSD). Additionally, the averages and standard deviations were obtained for the aforementioned accelerations and Keplerian elements. The numerous periodic components were identified. The characteristic resonances with the satellite orbital period, with the Earth’s rotation period and with the Moon’s synodic period were described.

5

Simplification of geopotential perturbing force acting on a satellite

Eshagh M., Abdollahzadeh M., Najafi-Alamdari M.

Artificial Satellites : Journal of Planetary Geodesy

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2008

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Vol. 43, No. 2

45--64

EN

One of the aspects of geopotential models is orbit integration of satellites. The geopotential acceleration has the largest influence on a satellite with respect to the other perturbing forces. The equation of motion of satellites is a secondorder vector differential equation. These equations are further simplified and developed in this study based on the geopotential force. This new expression is much simpler than the traditional one as it does not derivatives of the associated Legendre functions and the transformations are included in the equations. The maximum degree and order of the geopotential harmonic expansion must be selected prior to the orbit integration purposes. The values of the maximum degree and order of these coefficients depend directly on the satellite’s altitude. In this article, behaviour of orbital elements of recent geopotential satellites, such as CHAMP, GRACE and GOCE is considered with respect to the different degree and order of geopotential coefficients. In this case, the maximum degree 116, 109 and 175 were derived for the Earth gravitational field in short arc orbit integration of the CHAMP, GRACE and GOCE, respectively considering millimeter level in perturbations.