Orbital Prediction of GPS Satellites
Date Issued
2010
Date
2010
Author(s)
Hsu, Tin-An
Abstract
After GPS receivers being shot down for a long time, the time of booting may be too long due to the difficulty in obtaining the satellite’s position. In order to solve the problem and reduce the booting time, we use the GPS satellites positions prediction in this research to extend the useable time of GPS ephemeris such that the GPS receivers can be maintained in the condition of hot start. The Newton’s equation is integrated to predict the position of satellite since forces acting on the satellite in space do not only contain the Earth’s gravitational force. If we want to predicate the position of satellite precisely, we have to consider the other forces. The forces include the non–spherical Earth effect, Solar and Lunar gravitational effect, and Solar radiation pressure in this thesis. Moreover, the effect of attitude motion to the orbital prediction is discussed.
The ephemeris data in the GPS receivers is in the frame of WGS-84, but the Newton’s equation is calculated in an inertial frame. Therefore, we have to adopt the appropriate coordinate transformation between the two frames by including the effect of the precession, the nutation, and the polor motion of the Earth.
The forth-order Runge Kutta method is used to solve the Newton’s equation. The numerical results show that the prediction error of the satellites positions in one day can be reduced from ten of kilometers to ten or hundreds of meters after the perturbations being included. The designed prediction successfully predict the positions of GPS satellites very close to the actual positions.
Subjects
GPS satellites
Orbital mechanics
Non-spherical Earth
Solar and lunar gravitational effect
Solar radiation pressure
Numerical integration
Type
thesis
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