Flight Status of Robotic Asteroid Sample Return Mission Hayabusa2
Tsuda, Y., Nakazawa, S., Kushiki, K., Yoshikawa, M., Kuninaka, H., Watanabe, S.
The Japan Aerospace Exploration Agency launched the asteroid sample return spacecraft “Hayabusa2” on December 3, 2014. Hayabusa2 will reach the C-type asteroid 1999 JU3 in 2018, and return back to the Earth in 2020. Sample collections from three sites, four surface rovers deployment and a 4 MJ-class kinetic impact crater generation are planned in the 1.5 years of the asteroid-proximity operation. The mission objective of Hayabusa2 has three aspects, science, engineering and exploration, all of which would be expanded by the successful round-trip journey. This paper describes the outline of the Hayabusa2 mission and the current flight status after the seven month of the interplanetary cruise.
Generalized Attitude Model for Spinning Solar Sail Spacecraft
Tsuda, Y., Saiki, T., Funase, R., Mimasu, Y.
An attitude model for a general spinning solar sail spacecraft under the influence of solar radiation pressure is presented. This model, called “Generalized Spinning Sail Model”, can be applied to realistic sails with nonflat surfaces that have nonuniform optical properties. The unique behaviors predicted by the generalized spinning sail model are verified by actual operation of the Japanese spinning solar sail spacecraft IKAROS. It is shown how imperfections in the sail surface affect the attitude motion of spinning sails, and a compact mathematical model that can precisely reproduce the spin-averaged motion of the spinning sails is derived. The stability conditions and a reduced model that preserves the key characteristics of the generalized spinning sail model are also derived to reveal the unique properties of the attitude behavior of spinning sails.
Solar Radiation Pressure-Assisted Fuel-Free Sun Tracking and Its Application to Hayabusa2
This paper describes the modeling, dynamical characteristics, and implementation of an attitude control method that actively uses solar radiation pressure. The theory behind this control method is called the generalized sail dynamics model, which was developed by the authors and successfully applied to Hayabusa2, which is a Japanese asteroid explorer launched in 2014. The quasi-stable property of the dynamics is proved, which enables the implementation of a fuel-free sun-tracking attitude using only one reaction wheel. As of August 2016, the attitude of Hayabusa2 was maintained within 10 deg offset from the sun direction for 193 days in total without consuming any fuel. The auto-sun tracking, single-wheel, and fuel-free features were distinctive as compared to any other conventional control methods, such as three-axis stabilization, and brought many merits to practical spacecraft operations. The theoretical background, the prelaunch evaluation based on a finite element model analysis, the identification process of the dynamics model carried out for the Hayabusa2 mission operation, and their effectiveness are presented in this paper.