Research On Fast Algorithm For The Time Windows Of Satellite-ground Links And Inter-satellite Links

With the development of the astronautics, more and more resources are used to complete space tasks. The dynamic topology including satellite ground station links, reconnaissance links and inter-satellite links is formed through the connection among resource nodes. Research on fast algorithm for the time windows of satellite-ground links and inter-satellite links plays a key role in the planning and scheduling of space tasks. The main contributions of this paper are as follows:First, the fast algorithm for the time windows between the satellite and the ground station is investigated. A transcendental equation about the eccentric anomaly is proposed to compute the time windows between the J2 perturbed LEO satellite and the ground station, and this equation is solved by using the great circle to locally approximate the ground trace. The simulation results show that the start instant errors of the time windows are less than 1s, and the duration errors are less than 1.2s, with a 99.7% decrease in computation time over the classical propagation method. A space curve modeling technique known as parabolic blending is used to compute the time windows between the MEO satellite and the ground station. The simulation results show that the start instant errors of the time windows are less than 1.28s, and the duration errors are less than 1.30s; the computation time is decreased by 99.5%.Second, the fast algorithm for the time windows of reconnaissance links is investigated. We convert the computation of time windows between the conic FOV and the point target into the one between the satellite and the ground station, and use a novel concept, extended visibility area, to compute the time windows between the conic FOV and the polygonal or elliptic target. The local search method using the circumscribed cone of FOV is put forward to compute the time windows between the rectangular or side-glance FOV and the ground target. The simulation results show that the start instant errors of the time windows are less than 1.35s, and the duration errors are less than 1.29s; the computation time is decreased by 99.5%.Third, the fast algorithm for the time windows between the relay satellite and the user satellite is proposed, and the inter-satellite communication performance of LEO early warning constellation is analyzed in the connectivity and the performance of delay. In the fast algorithm, the models of three types of visibility spherical caps are established by analyzing the communication links between the relay satellites and the user satellites. By using the circle locally approximation to the ground trace, the time windows are estimated. The simulation results show that the start instant errors of the time windows are less than 0.2s, and the duration errors are less than 0.23s; the computation time is decreased by 90%.The advantage of these algorithms is the greatly reduced computational amount, making it attractive for supporting the planning and scheduling of space tasks.