Dynamics and orbit determination of tethered satellite systems

Most analyses of tethered satellite systems have been focused on the relati ve motion of the satellites either with respect to each other, or with resp ect to their center of mass. In this paper, we consider how the motion of o ne of the satellites in a two-body tethered system is perturbed by the pres ence of the other. This point of view is necessary if the orbits of the sat ellites in such a system are to be determined correctly when the fact that they are tethered is not known a priori, Rather general equations of motion for the satellites are derived. These equations are simplified by assuming planar motion. From the simplified equations, an expression for an "appare nt" gravitational constant is derived. Then, the identification and state d etermination problem is addressed. Examples obtained using a conventional l east-squares batch processor are discussed. It appears that a two-stage met hod, using both two-body and tethered satellite dynamic models, is a good w ay to identify and determine the states of some tethered satellite systems.