Interplanetary Magnetic Attitude Control in Small Sized Spacecraft

Recently, nano-spacecraft are being used in interplanetary missions. To achieve their mission goals, generally, spacecraft attitude should be controlled and stabilized for obtaining scientific data and communicating with ground stations. Reaction wheels (RWs) and thrusters have been utilized as actuators in attitude control systems in a number of interplanetary spacecraft. These actuators are useful for attitude control; however, it is difficult to install them in all nano-spacecraft because of strict limitations of mass and power consumption. Particularly, to enable attitude control during an entire mission, a spacecraft needs to have a larger amount of fuel than expected amount in its nominal case in the design phase to allow for the worst-case scenario. Furthermore, RWs and thrusters generally have complicated structures; therefore, the system degrades the reliability of the bus system, including power and communication subsystems, which sometimes cannot be utilized without the attitude control system. For a high-reliability and low-mass attitude control system, this research proposes an attitude control system for nano-spacecraft using a magnetic torque generated by an electromagnetic coil in an interplanetary magnetic field. Because the proposed system utilizes an electromagnetic coil, the system does not require fuel for the attitude control system. Moreover, since electromagnetic coils generally have simple structures and electronic circuits, the spacecraft can achieve higher reliability in its bus system. Consequently, the spacecraft can reduce the mass for the fuel using a system with higher reliability than conventional systems. In this research, we propose the application of the electromagnetic coils for passive attitude control and unloading for RWs in interplanetary orbits.