We investigate the Pursuit-Evasion Differential Game (PE Game) for satellites with continuous thrust from the viewpoint of reachable domain (RD). A concept of hyperreachable domain(HRD) is introduced to help analyze the problem, and a sufficient condition for capture in a PE game is proposed based on the players' HRD. Meanwhile, to practically use the RD as a tool to analyze the PE game, an analytical form of the satellite's reachable domain is deduced based on the Clohessy Wiltshire(CW) model. The simplicity and accuracy of the CW model in solving the RD render it practicable to apply the sufficient condition in studying the PE Game of continuousthrust satellites.

Solar sail spacecraft are proposed to accomplish body-fixed hovering missions over elongated asteroids. The body-fixed hovering flight is to maintain a fixed position relative to the surface of the spinning asteroid. A solar sail without fuel consumption can greatly expand the range of hovering locations in a variable lightness number for an extended period. A rotating mass dipole is used to produce the gravitational field created by an elongated asteroid. Dynamic equations are obtained for the approximate model in terms of the specified hovering conditions. Feasible hovering regions over elongated asteroids are presented and analyzed via numerical simulations. A parametric study is made to investigate the influence of solar latitude angles and the lightness number on the feasible hovering region. The hovering orbits around the realistic asteroid 951 Gaspra are performed to evaluate the effectiveness of the method in this paper.

The use of the electrochromic device has been proposed for the attitude control of spacecraft for decades because its optical characteristics can be altered by electrical excitation. The technology was recently employed and verified successfully on Interplanetary Kite Craft Accelerated by Radiation of the Sun, the world’s first interplanetary sailcraft. In addition to its ability to control the attitude of a solar sail, the reflectivity control device can also be used directly for the orbit control of the sail. In this study, a new approach for joint active orbit and attitude control of a sail using the reflectivity modulation technology is proposed. The force and torque models of a reflectivity modulated spinning disk sail experienced by solar radiation pressure are discussed, and two reflectivity modulation modes are provided and compared in terms of control performance. One mode, which was used in the Interplanetary Kite Craft Accelerated by Radiation of the Sun mission, is investigated for the active ...