ABSTRACT The Fourth International Symposium on Solar Sailing 2017 17th - 20th January, 2017, Kyoto, JAPAN

Title of Paper Fuel-free Attitude Control of Bias-momentum Solar Sail

Corresponding Author Name Yuya Mimasu Title Dr. Affiliation Japan Aerospace Exploration Agency

Co-Authors Name Go Ono Title Dr. Affiliation Japan Aerospace Exploration Agency

Co-Authors Name Yuichi Tsuda Title Dr. Affiliation Japan Aerospace Exploration Agency

Abstract

Solar sail is the fuel-free thrust system. Its trajectory can be changed without fuel by using the solar radiation pressure (SRP) induced by the sail. In general, however, the direction and the magnitude of the photon acceleration are controlled by the attitude of the sail, and the attitude control fuel is required. That is why, it is necessarily to reduce the fuel consumption of the attitude control in order to be a real fuel-free solar sail. This research is one solution for this issue. The SRP is affected not only to the orbit, but also to the attitude of the spacecraft. This effect can be utilized to control the attitude of spacecraft. There is an appropriate example on Hayabusa2 case during coasting phase. The attitude dynamics model of the Hayabusa2 under the SRP had been studied. Especially, the attitude motion in the one-wheel bias-momentum control mode has been modeled in detail, and calibrated by using the actual flight data of Hayabusa2. The one-wheel bias-momentum control mode is the control mode in which the spacecraft is controlled by using only Z-axis reaction wheel. In this mode, the attitude follows an angular momentum vector, and this angular momentum vector precesses due to the SRP. According to the established model and flight result of Hayabusa2, the equilibrium point of precession trajectory is changed by the body-phase angle with respect to the Sun direction. By utilizing this feature, the direction of angular momentum vector can be controlled by changing phase angle with respect to the Sun angle. The phase angle can be changed only by using one reaction wheel of Z-axis and usually unloading is not needed because just change the attitude orientation around Z-axis. It means that the spacecraft attitude can be controlled without fuel. This attitude control method can be applied to any bias-momentum spacecraft under certain condition determined by the balance between an angular momentum and SRP torque. In this paper, the application example to the solar sail and its applicable limit are evaluated. In addition, the orbit control feasibility in the case using this attitude control method is also discussed.