Research On Visibility Of LEO Satellites

The visibility of satellite mainly consists of the visibility-time, the entry-access and exit-entry time instant of the satellite to the ground terminal. The research on the visibility of satellite is very important in many applications, such as the design of satellite system, the performance evaluation of a satellite constellation, aerospace mission analysis, the military simulations, etc. According to the altitude of satellites' orbit, the satellites on the track could be classified into four types: low earth orbit satellite (LEO), Medium earth orbit satellite (MEO), geosynchronous earth orbit satellite (GEO), highly Eccentric orbit satellite (HEO). In this thesis, we have investigated the problem of the visibility of LEO satellite and laid emphasis on the fast algorithm for LEO satellite's visibility. The fast algorithm is very important to improve simulation efficiency, particularly in the event-driven and time-stepped real-time simulation environments.Firstly, the basic concepts and knowledge of two-body problem is introduced. And then, the algorithm for the visibility of circle orbit's LEO satellite to the ground terminal, shift orbit intersects circle compensation algorithm (SOICC), is developed. A novel concept, visibility spherical cap, is presented to determine whether the satellite is visible to the terminal. The concept plays a key role in the algorithm and its expanded applications. The great circle arc is used to approximate the sub-satellite track within the visibility window. The simulation results show that for the algorithm the time instant error at the entry-access and exit-access position is about 0.92 seconds.Secondly, the fast algorithm for the visibility of the elliptical orbit's LEO satellite, true anomaly iteration compensation algorithm (TAIC), is put forward. TAIC algorithm is the one which applies the main ideas of SOICC algorithm to the elliptical orbit. The most advantage of TAIC algorithm is that the main object for algorithm to deal with is true anomaly but not time instant. Therefore, Kepler Equation, a transcendental equation, could be avoided solving by numerical methods. Accordingly, the computation of TAIC algorithm is very small. The excellent performance of the algorithm is illustrated by the numerical results. For TAIC algorithm, the error of the entry-access time instant and the exit-access time instant is about 0.79 seconds.Thirdly, TAIC algorithm is expanded to apply in other areas, such as LEO satellite observing the fixed target, the link between the relay satellite and user satellite, etc. And the numerical results are showed. The other applications are also discussed.Finally the thesis is concluded and the future research areas are pointed out.