Analysis of Lunisolar Resonances in an Artificial Satellite Orbits

The present work deals with constructing a conditionally periodic solution for the motion of an Earth artificial satellite taking into account the oblateness of the Earth and the Luni-Solar attractions. The oblateness of the Earth is truncated beyond the second zonal harmonic 2 J . The resonances resulting from the commensurability between the mean motions of the satellite, the Moon, and the Sun is analyzed. INTRODUCTION In celestial mechanics, resonance occurs frequently when some of the quantities characterizing the motion of two or more orbiting bodies, e.g. periods of revolution, can be considered as commensurable, i.e. their ratio is close to an integer fraction. In a simplified form, this can be expressed as; 1 2 1 2 : : T T p p = where 1 T and 2 T are the actual values of the quantities involved, while 1 p and 2 p are positive integers ( 1,2,3,.......... 1 2 p p ≤ ) The phenomena of resonance can stabilize the orbits and protect them from gravitational perturbation, such that the orbiting bodies exert a regular gravitational influence on each other. The resonance problems are usually manifested by the appearance, when integrating the equations\ of motion, of small divisors. The main types of resonances were immediately recognized in the pioneering era (nearly 40 years ago) of artificial satellite theory: the critical inclination in the main problem, tesseral/sectorial resonances, and lunisolar resonance. The first two categories have attracted a lot of attention and each of them possess a vast bibliography. The more surprising, is the fact that the problem of lunisolar resonances has remained seriously underrated. Quite 1014 F. A. Abd El-Salam et al possibly it was due to the lack of interest in the effects whose typical time scale may exceed decades or even centuries, but this situation has changed once we realized the danger imposed by space debris, Breiter (2001). Eccentric and inclined resonant orbits are becoming of more interest. This is due to their use (i) in tracking and navigation satellite systems, (ii) for communication systems at high latitudes, (iii) for communication satellites intended to avoid the highly populated geosynchronous equatorial region, and (iv) for various planetary orbiters. Due to the importance of these commensurate orbits, they have received much attention, Radwan (2002). The literature is wealth and extensive with works dealing with the subject of resonance in artificial satellite orbits, and it seams worth to sketch some of the most important works: Celletti, (1990) studied the stability of spin-orbit resonances when exact commensurabilities between the periods of rotation and revolution of satellites or planets exist. He applied the Kolmogorov-Arnold-Moser theory to construct invariant surfaces trapping the synchronous resonance from above and below. Gilthorpe, et al. (1990) determined the orbital parameters of Cosmos 1603 (1984106A) when the satellite was close to 14:1 resonance. The author's analysis of the inclination and eccentricity enabled yielded six lumped harmonic coefficients of order 14. Analysis of the mean motion yielded additional pairs of lumped harmonics of orders 14, 28 and 42, the 14th-order harmonics superseding those obtained from analysis of the inclination. The derived values were used to test the Goddard Earth Models, GEM-T1 and GEM-T2, at high order. Delhaise and Morbidelli, (1993) studied a two-degrees of freedom problem of a geosynchronous artificial satellite orbiting near the critical inclination. Costa Filho and Sessin, (1999) has been concerned with the extended Delaunay method as well as the method of integration of equations , applied to first order resonance . The equations of the transformation of extended Delaunay method are analyzed in the 1 p p + type resonance problem with more than one degree of freedom. Breiter (1999) studied the eccentricity resonances between the secular motion of an Earth satellite's orbit and the longitudes of the Sun and the Moon within a Hamiltonian framework. The author identified a family of 10 resonances, stable and unstable points. He estimated also the libration widths. The author gave numerical values for the maximum variation of eccentricity available at each resonance. The respective amplitudes of the perigee heights' librations range from 2 to 750 km. The author concluded that resonances of the solar origin are generally stronger than their lunar counterparts. Celletti and Chierchia, (2000) investigated the behavior of `resonances' in the spinorbit coupling in celestial mechanics in a conservative setting. They considered a Hamiltonian nearly-integrable model describing an approximation of the spin-orbit interaction. The continuous system is reduced to a mapping by Analysis of lunisolar resonances 1015 integrating the equations of motion through a symplectic algorithm. The authors studied numerically the stability of periodic orbits associated to the above mapping by looking at the eigenvalues of the matrix of the linearized map over the full cycle of the periodic orbit. A plot of the critical function versus the frequency at different orbital eccentricities shows significant peaks at the synchronous resonance (for low eccentricities) and at the synchronous and 3: 2 resonances (at higher eccentricities) in good agreement with astronomical observations. Breiter (2000) studied two degrees of freedom system to heck how a coupling of two lunisolar resonances affects the results furnished by the analysis of an isolated resonance case. The author identified in this system with two critical angles seven types of critical points. The critical points arise and change their stability through 11 bifurcations. If the initial conditions are selected close to the critical points, the system becomes chaotic. Breiter, (2001) reviewed all single resonances, attaching an appropriate fundamental model to each case. Only a part of resonances match known fundamental models. An extended fundamental model is proposed to account for some complicated phenomena. Most of the double resonance cases still remain unexplored. The basic model including the Earth's 2 J and a Hill-type model for the Sun or the Moon admits 20 different periodic terms which may lead to a resonance involving the satellite's perigee, node and the longitude of the perturbing body. Breiter (2003) proposed a new, extended fundamental model (EFM) in order to improve the classical, Andoyer type, second fundamental model (SFM). The EFM Hamiltonian differs from the SFM by the addition of a term with the third power of momentum; it depends on two free parameters. The new model is studied for the case of a first-order resonance, where up to five critical points can be present. Similarly, to the respective SFM, it admits only the saddle-node bifurcations of critical points, but its advantage lies in the capability of generating the separatrix bifurcations, known also as saddle connections. The author performed a reduction of parameters for the EF in a way that allows the use of the model in the case of the so-called abnormal resonance. El-Saftawy (2005) analyzed the resonance terms produced by the effect of direct solar radiation pressure on the motion of an axially symmetric spacecraft in the oblate Earth field. He developed a canonical transformation technique based on the Bohlin technique. The author applied the developed technique to the problem averaged over the mean anomaly, which is suitable in the presence of more than one resonant vector. The present work treats the resonances arising from the commensurability between the mean motions of the satellite, the Moon, and the Sun. The conditions of the resonance are determined and developed to suit the programming process. Analyses of these conditions are preformed for different selected orbits. Problem Statement We consider the motion of an artificial satellite in the Earth's gravity fields and perturbed by lunisolar attraction. 1016 F. A. Abd El-Salam et al Let us assume, with sufficient accuracy, the following assumptions:(1) The geopotential is restricted to the 2 J part, like in the main problem of artificial satellite theory. (2) Sun and Moon move in circular orbits in the fixed ecliptic plane. Then we can set 2 2 ., u n t cont = + and 2 2 ., u n t cont = + , where 2 2 ( , ) u n and 3 3 ( , ) u n are the argument of latitude and the mean motion of the Moon and the Sun respectively. Noting that the time t appears explicitly through 2 u and 3 u , we augment the set by the addition of the pair 2 2 ., k n t cont = + 3 3 ., k n t cont = + and their conjugates 2 K and 3 K respectively. Lunisolar potential are truncated at the second Legendre polynomial term. The normalized Hamiltonian Considering 2 n as the small parameter of the problem, the orders of magnitude up to the second order of the involved parameters are defined as follows 2 0.03 ( ) n O zero = ≡ . The normalized Hamiltonian of the system considered, ** Η , after eliminating the short and intermediate period terms respectively using a perturbation technique based on Lie series and Lie transform can be represented as, Radwan (2002) ∗∗ ∗∗ ∗∗ ∗∗ = 0 1 2 Η Η + Η + Η (1) Where 2 2 2 2 K L μ ∗∗ ⊕ = − 0 Η (2) 2 30 33 3 AK γ θ η ∗∗ = + 1 Η (3) 2 2 2 4 2 3 5 2 0 2 cos( ) k ij k i j L B kl il jl ∗∗ =− = =− = + + ∑ ∑∑ 2 Η (4) with 2 2 2 2 0 0 0 00 1 0 3 24 10 1 1 02 3 25 3 3 3 3 (1 ) (1 ), (1 ), (1 ), 2 2 2 2 e e e e B A A B A B A θ θ θ θ = + + + = + = + 2 2 2 2 2 2 2 2 1 1 1 1 00 25 10 1 5 10 5 1 20 3 4 5 5 5 5 , ( ), ( ), ( ), 2 2 2 2 A e A e A e A e B B B B θ θ θ θ θ θ θ − − − = = + = − = − 2 2 2 2 2 2 2 2 3 1 1 1 20 3 4 02 25 26 20 25 26 2, 2 27 5 5 5 5 ( ), ( ), ( ), , 2 2 2 4 A e A e A e A e B B B B θ θ θ θ θ θ θ − − = + = − = + = 2 2 2 2 2 2 3 3 3 2, 2 28 29 2, 2 28 29 22 27 5 5 5 ( ), ( ), 4 4 4 A e A e A e B B B θ θ θ θ θ − − − = + = − = , where 0, 2; 0,1,2; 0, 2; 0,1,2 k i j s = ± = = ± = , ' 1 , ( 1,2,..) ij i i i s i L G η θ = = are evaluated in appendix I in Radwan (2202), and 1 2 , , , A A A γ are zero order quantities defined by Analysis of lunisolar resonances 1017 2 4 3 3 2 2 1 1 2 4 2 3 4 2 3 2 2 2 2 2 3 2 9 9 , , , 2 2 2 n R J A A A n n a n a n μ μ μ γ μ μ ⊕