Descent and touchdown dynamics for sample collection in hayabusa mission

Paper number

IAC-06-C1.3.02

Author

Dr. Takashi Kubota, Japan Aerospace Exploration Agency (JAXA)/ISAS, Japan

Year

2006

Abstract

Small planetary bodies such as asteroids, comets and meteorites have received worldwide attentions in recent years. These studies have been motivated by a desire to shed light on the origin and evolution of the solar system. Institute of Space and Astronautical Science (ISAS) of JAXA has promoted the asteroid sample return mission MUSES-C. In MUSES-C mission, Hayabusa spacecraft stayed around the asteroid Itokawa for about three months in 2005 and performed the final descent and touchdowns twice in November 2005. In final descent phase, terrain alignment maneuvers were accomplished to control both altitude and attitude with respect to the surface by using four beams Laser Range Finder onboard. Then Hayabusa spacecraft made dynamic touchdowns the surface of the asteroid by the sampler system to collect samples automatically. The sampling method of Hayabusa is so-called touch and go way, that is, the spacecraft shoots a small bullet to the surface just after touch-down has detected, collects ejected fragments with sampler horn, and lifts off before one of solar cell panels might hit the surface.
In the sample return mission, the contact with the surface of the asteroid is one of the most critical events. In order to make sure the safety, in terms of the strength of the structure against the impulsive force and the attitude maintenance against the impulsive moment, it is necessary to carefully design the sampling mechanism and the control systems. Different from the large planets, the asteroid is a very small object whose gravity field is too little for any sampler to dig and drill the surface. Nevertheless, the spacecraft has to cope even with the hard surface such as rocks, while it is requested to function for soft surface like sands as well. Therefore, a novel sample collection scheme is developed by the combination of the Shooting Projectile and the Fragment Catcher. The dynamic motion of the free-flying multi-body system is also described with the presence of the external forces. The magnitude of the forces is determined by the compliant deformation and friction of the contact surface. 
This paper presents the terrain alignment maneuver and touchdown scheme. This paper also describes the novel sample horn system and dynamics. The dynamic behavior is analyzed with use of knowledge on the free-flying and contact dynamics. This paper presents an attitude control scheme by RCS off-modulation after lift-off. Finally the flight results on touchdown dynamics are shown and discussed.

Abstract document

IAC-06-C1.3.02.pdf

Manuscript document

IAC-06-C1.3.02.pdf (🔒 authorized access only).

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