The main point of this paper is to evaluate the perturbations in orbital elements of a low Earth orbiting satellite. The outcome of a numerical orbit integration process is the position and velocity vectors of satellite in an inertial coordinate system. The velocity and position vectors are converted into the corresponding orbital elements. Perturbations in a satellite motion affect the orbital elements in the sense of Keplerian motion. In this paper after introducing the perturbing forces acting on a satellite, the method of converting the position and velocity into the orbital elements is presented, and finally the perturbations in orbital elements of the low Earth orbiting satellite of CHAMP are evaluated. The numerical results show that, disregarding the geopotential perturbing forces, the air drag is the most predominant among other perturbing forces: rotational deformation, solar radiation, third body effect, solid Earth tide, ocean tide, and general relativity arranged by their magnitude respectively.
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