This paper addresses the spectral coexistence between LEO constellation and GEO belt for global distributed earth stations. A specific method is introduced to mitigate the in-line interference by tilting the direction normal of phased array antennas of LEO satellites, and the optimal direction is found by solving a non-linear programming problem. The simulation results prove that the proposed approach leads to greater link availability while guaranteeing the desired received signal level especially for low-latitude earth stations.

The orbital accessibility problem for spacecraft is to determine whether a transfer to a given target is accomplishable with limited fuel consumption. In this study, limited fuel consumption is conveniently expressed in terms of a single available impulse. By using the terminal velocity hyperbola of the orbital two-point boundary value problem, a geometrical description of the accessibility condition is attained and then further converted to an algebraic description through the analytic geometry for the convenience of numerical computation. Three typical applications are suggested: 1) solving the orbital accessibility problem when the available impulse magnitude and the target position are both given, 2) searching for the minimum impulse required when the target position is given, and 3) calculating the reachable domain when the available impulse magnitude is given. Numerical examples are presented to validate the proposed method and to demonstrate its three typical applications.

In space systems consisting of a large number of satellites, coordinating orbits among satellites is necessary throughout the entire mission lifetime. Although previous works mainly focused on the boundedness of relative motion between satellites in the group, in this paper, an extra degree of freedom is also addressed in order to manipulate an arbitrary number of orbital elements, which is represented as coordinating a general orbital transfer and an in-space assembly. The underlying concept is using consensus theory to characterize the properties of the control objective as in a multiagent system. To that end, this paper assumes that the communication in the networked satellite system is represented as an undirected graph, and then implements the governing system dynamics in a control-affine form as described by the Gauss's variational equations. For the general orbital transfer problem, an edge-error-based controller is developed and proven asymptotically stable. Definitions of error functions are also investigated to understand the behavior of developed controllers. Several strategies for assembly control are discussed, namely, via changing of variables or in a two-phase control process based on the dynamical structure. Numerical simulations are performed to validate the analysis and demonstrate the results.