ANALYZING THE EFFECT OF NONSPHERICAL EARTH ON SATELLITES ORBITAL ELEMENTS AT DIFFERENT ALTITUDES.
AHMED K. IZZET Technical Engineering College, Kirkuk, Northern Technical University, Iraq.
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Abstract The gravitational field of Earth is not entirely isotropic; rather, its values change dramatically with one's orientation. Changes in its interior density and nonspherical shape are the reason. These gravitational anisotropies affect a spacecraft's orbit around the Earth, causing slightly distorted Keplerian orbits. When we get close enough to track a satellite's motion, we may see that it deviates from this Keplerian motion. Throughout a single revolution, the difference is negligible; still, it gradually grows over time, becoming noticeable after a few days. It is possible to describe the Keplerian orbit as gradually deformed. Orbital elements are what distinguish a certain orbit in celestial mechanics. These elements are required to describe the motion of celestial bodies in space as well as to predict and understand their trajectories. Artificial satellite orbit theory about the study of the Earth's external gravitational field, the goal of satellite orbit theory is to establish a relationship between orbital parameters and gravitational field features, like coefficients, using a description expressed in terms of spherical harmonics. When tracking satellites, the physical effects resulting from the zonal harmonics are crucial because they show how the earth's actual shape differs in latitude from the symmetric earth. This is due to the fact that the earth's density might differ, either higher or lower, at one latitude point compared to another. The orbit of a test satellite is integrated over a comparatively short period of one day using the celestial mechanics program. Eccentricity, inclination, and semi-major axes all have periodic effects; however, the other three factors show a secular change in addition to brief periodic variations. Based on the results, we may conclude that as the satellite's altitude increases, the gravitational potential’s impacts on its orbital elements decrease. The amount to which variations in the satellite's altitude impact osculating Keplerian compounds in radi.al, along-track, and out-of-plane directions relative to the starting orbit were also examined in the study. The results showed that the degree to which a satellite influences gravitational potential depends critically on its elevation. We infer that the mass distribution is not precisely spherically symmetrical and because there is a non-spherical discrepancy between the actual motion and the ideal Keplerian motion affected by the Earth
Keywords
Zonal Harmonics, Asymmetrical Gravitational Field, Keplerian Motion, Perturbations, |