Solar Radiation Pressure and Gravitational Waves Effects on Sun-Synchronous Orbits

For certain values of semi-major axis and eccentricity, orbit plane precession caused by Earth oblate is synchronous with the mean orbital motion of the apparent Sun (a sun-synchronism). Many forces cause slow changes in the inclination and ascending node of sun-synchronous orbits. In this work, we investigate the analytical perturbations due to the direct solar radiation pressure and gravitational waves effects. A full analytical solution is obtained using technique of canonical Lie-transformation up to the order three in 2 J (the oblateness of the Earth). The solar radiation pressure and gravitational waves perturbations cause second order effects on all the elements of the elliptic orbit (the eccentricity, inclination, ascending node, argument of perigee, and semi-major axis) consequently these perturbations will cause disturbance in the sun-synchronism. Also we found that the perturbation or the behavior of gravitational waves almost the same as the perturbation or the behavior of solar radiation pressure and their coupling will incorporate the sun-synchronism through the secular rate of the ascending node precession.


Introduction
It is well known that the sun-synchronous orbits are useful for remote sensing mission, because the illumination of the sub satellite point (the point where a straight line drawn from a satellite to the center of the Earth intersects the Earth's surface) is nearly constant on each successive pass.Also sun-synchronous orbits must be retrograde (i.e.inclination greater than 90˚).If the sun-synchronous orbit is high enough and the sub satellite point is initiated outside the Earth's shadow, then the illumination of the sub satellite point will be remain conti-nuously throughout the year.Since a sun-synchronous orbits follows the Sun, so the solar pressure perturbations cannot be neglected, if the orbit is un-shadowed, long period occur in all the orbital elements except semi-major axis [1] [2].It is well known that Earth oblateness causes the orbital angular momentum vector of earth satellite to process about the Earth's polar axis.For certain value of semi-major axis and eccentricity orbit plane precession caused by oblateness is synchronous with the mean orbital motion of the apparent Sun (a sun-synchronism).Gravitational perturbations arising from a spherical Earth, Moon, and Sun cause long period fluctuations in the mean argument of perigee, eccentricity, inclination, and ascending node [3].Relativistic effects with SRP incorporate the sun-synchronism [4].The short and long period's perturbations due to the effect of GW on the orbital elements of Jupiter are studies by [5].Semi-analytical theory of the mean orbital motion due to the effect of gravitational waves is investigated by [6].Many authors discussed the effect of solar radiation pressure and the effects of gravitational waves separately but the purpose of the current contribution is to investigate the coupling effects of solar radiation pressure and gravitational waves on sun-synchronism of elliptic orbits, using the perturbation technique based on the canonical Lie-transformation.Two canonical transformations obtained to eliminate the short-period and long-period terms.The solution is obtained up to order three and two in secular and periodic terms respectively assuming the effect of direct solar radiation pressure and the gravitational waves of the same order of magnitude and equal to the order of 2 2 J (the second order zonal harmonic of the geo potential i.e. 10 −6 ).

The Formulation
The Hamiltonian which describes the moving Earth's satellite under the influence of SRP and the GW can be expressed as where g H represents the Hamiltonian of a satellite in the Earth's gravitational v is the velocity of satellite, P is the canonical momentum, and L is the Lagrangian of a satellite moving about a central body in Einstein form of the post Newtonian gravitational field [7] where l c is the speed of light and N U the Earth's gravitational potential is developed in series up the fourth harmonic as [8] ( ) ( ) ( ) where R is the equatorial radius of the Earth, δ is the latitude referred to the equatorial plane, i is the inclination of the orbit plane, f the true anomaly, ω the argument of perigee, and  is the semi-major axis as in Figure 1.Then the Hamiltonian g H will be in the form where   The Hamiltonian of the solar radiation pressure s H in terms of Delaunay elements is given by [9] { } { } ( n is the solar mean motion of order unity rather than ( ) is the conjugate of 4s L which will be found from , є is the obliquity of the ecliptic, and β is constant which represents satellite area to mass ratio corresponding to a spherical satellite.
Finally the Hamiltonian of the gravitational waves w H in terms of Delaunay elements is given by ( where n is the frequency of the wave. 1 α and 2 α are the phase difference, h + and x h are the amplitudes of the wave in the two orthogonal directions in the transverse plane.4w According to Equations ( 5), (6), and ( 7) we can write the Hamiltonian H in (1) where є is the small parameter of the expansion which represents the second zonal harmonic 2 J of the Earth's potential, and For different orders of 2 J , the coefficients A's are The second-order term in the Hamiltonian H which is given in Equation (10) is consisting of the non-relativistic terms

The Algorithm of Solution
where i L and i l are the set of the Delaunay variable in Equation ( 4).H is the Hamiltonian in equations from ( 9) to (16).We use Lie transform to solve our problem [10] [11].This method is one of the canonical perturbation methods proposed to build successive canonical transformation for Hamiltonian systems depending on a small parameter based on the consideration of Lie series and Lie transform.The system of Equation ( 17) will be solved up to order three in secular terms by performing two successive canonical transformation , ′′ ′′ analytic in є at є 0 = to eliminate the short and long period terms, respectively from the Hamiltonian, where the primes indicate the transformed variables.The transformed Hamiltonians are in the form With generators W and The algorithm for eliminating the short-period terms (i.e.those depending on l and 4 l ) determining the new Hamiltonian * H and the generator W is Zero order: , , d where the subscripts s and p indicates the secular (averaged over g′ ) and the periodic parts in g′′ .Finally, the remaining secular problem, being indepen- dent of all angle variables.The elements of the short period are obtained from ( ) where the prime indicate the transformed terms.For the inverse transformations Similarly for the elements of the long period.

Third Order Solution
We employ the previous algorithms to obtain analytical expressions for the short-period and long-period terms of the orbital elements; the solution is expressed in terms of the Delaunay variables.We obtain the following results.

The Short-Period Terms
Zero order: First order: Second order: where E is the eccentric anomaly and the (b) coefficients are coefficients depend on the eccentricity, c and s (i.e. the inclination) and these coefficients is coming from the expansion of a r , cos a f r , sin a f r in the Hamiltonian H World Journal of Mechanics Third order: ( This order represents the joint effects of the relativistic effect and the solar radiation pressure and GW effects, ( ) ′ is the differentiation of s T with respect to 4 l .From the generators 1 W and 2 W we can determine the ele- ments of the short-period transformation and its inverse according to the Equations ( 22) and (23).

The Long-Period Terms
We now proceed to performing a second canonical transformation to eliminate 4 4 , , , w g h l l ′ ′ ′ ′ (the argument of perigee, the longitude of node and the augmenta- tion variable of the mean motion of the Sun n and the frequency of the gravi- tational waves w n ) from the Hamiltonian.This transformation contains the long-periodic perturbations, whereas the secular terms will be derived from the canonical equations of motion and the final Hamiltonian ** H .For the simplic- ity of writing we dropped the primes.Zero order: First order: Second order: ( ) The corresponding generators coming from the Newtonian effect, the relativistic effect, the solar radiation pressure effect and gravitational waves effect are respectively Third order: L G H L g h l then we found that there is long-period perturbation in all elements of the orbit due to the relativistic effect, the solar radiation pressure effect, and the joint effect of solar radiation pressure and gravitational waves, except the semi-major axis.

The Secular Terms
Now both short and long-period terms have been eliminated, the new Hamiltonian ** H contains no angular variables ( , , , , w l g h l l ), therefore according to Equations (53), (54), (55), (56), and (17), the action variables , , L G H ′′ ′′ ′′ are constants (consequently the semi-major axis a, the eccentricity e, and the inclination i have no secular effects due to the joint of relativistic effect and solar radiation pressure effect and the joint effect of SRP and GW), and the angular variables , , l g h ′′ ′′ ′′ (have secular effects due to the joint effect of SRP and GW) are expressed in the form

Conclusion and Discussion
In this work, we analyze analytically and investigate the coupling effects between solar radiation pressure and gravitational waves.All calculations of the shortperiod, and long-period were obtained up to the order three in 2 J (earth's zonal harmonic), which represents the coupling between the relativistic effect and the influence of direct solar radiation pressure and the coupling between

Figure 1 .
Figure 1.The position vector of moving celestial object in XYZ.

H
and the terms of gravitational waves 25 H .The third order term 3 H is representing the mixed perturbation due to Newtonian quadruple field and Schwarzschild acceleration.
j are integers), and the corresponding generators are ) } , and the generator of joint effect of solar radiation pressure and gravitational waves