Analysis of the orbital motion of a general tethered satellite system.

摘要

This dissertation addresses problems associated with the orbital motion of a general tethered satellite system. Of particular interest are the problems of detecting the fact that a satellite is tethered and determining the motion of the system. A mathematical model for the orbital motion of a general tethered satellite system (GTSS) is developed and the dynamic characteristics of the model are analyzed by numerical and analytical methods. The general tethered satellite system model describes the orbital motion of a two-satellite tethered system very well. The dynamic characteristics of a GTSS are then studied using a “perturbed two-body motion” approach. Perturbations of the motion of one satellite due to the other tethered satellite are investigated. This approach is adopted so that the identification and determination of the orbit of one of the satellites can be attempted without using observations of the motion of the other satellite in the system. Approximate solutions to the orbital motion of a GTSS and the relative motion of the tethered satellite are obtained by using analytical methods. A new method for the identification and motion determination of a GTSS by using a least square batch filter is described. In this method, the apparent gravitational constant and a tether parameter are used as indices for identifying (detecting) the observed satellite as a member of a tethered satellite system. The identification and motion determination are treated by using separate methods. These methods provide means for tethered satellite detection, system identification, and motion prediction. First the identification of the observed satellite as one in a GTSS is made. Second, the approximate solution for the orbital motion of the observed satellite as a member of the a GTSS is used to obtain estimates of the reduced number of states using a batch least square filter. Third, the equations of motion of a GTSS are used to obtain refined estimates of the states that define the orbital motion and those that define the librational motion. This process reduces the difficulty inherent in the low observability of the librational motion.