Osamu Mori

Laboratory for Space Systems, Tokyo Institute of Technology and JAXA/ISAS have proposed tethered sampling method for future asteroid sample returning mission. The tethered sampling mission consists of three procedures: shooting a tethered sampler, a corer, at a high velocity, penetrating the corer into a surface and collecting soil inside, and reeling in the tether and retrieving the corer and soil. This paper reports a dynamics model of tethered corer and tether deployment experiments. The experiment results show validity of the model and effect of bobbin shapes and projection directions on corer and tether behavior which directly give guidelines to system design of corer projection.

The paper presents the attitude reorientation taking the advantage of solar radiation pressure without use of any fuel aboard. The strategy had been adopted to make Hayabusa spacecraft keep pointed toward the Sun for several months, while spinning. The paper adds the above mentioned results reported in Sedona this February showing another challenge of combining ion engines propulsion tactically balanced with the solar radiation torque with no spin motion. The operation has been performed since this March for a half year successfully. The flight results are presented with the estimated solar array panel diffusion coefficient and the ion engine's swirl torque.

This paper describes the attitude dynamics and the control method of a spinning solar sail spacecraft. The solar sail considered here has no structure supporting membrane, therefore estimation of the effect of membrane flexibility is one of the problems to solve for the future validation flight. In this study, we established a dynamic model including membrane vibration to handle a coupled motion of a rigid spacecraft and a flexible membrane, and focus on the consideration of attitude control method. The result is confirmed with numerical simulation by use of Multi Particle Model(MPM).

This paper presents what the Hayabusa spacecraft experienced when it restarted the three axis stabilization. Due to the loss of two wheels aboard and also due to the loss of fuel, the primary axis of inertia of the spacecraft was tilted offset to the geometrical axis. The instability was observed unexpectedly since there was little thought about the instability associated with the single wheel system. The results can be applied for other spacecraft. The flight results are shown as well.

This paper describes the navigation and the guidance strategy of the small spacecraft for flyby using the images of the target. We derived navigation and guidance accuracies of this mission analytically, and confirmed them by numerical simulation. For high accurate flyby, the center of the target needs to be measured accurately. However the shade area on the target surface makes it difficult to know the target center position from the information of the center of brightness in image. This uncertainty affects the guidance accuracy from the target. In this paper, a method to calculate the target center from the tangent points of the sun is proposed. The validity of the method is examined in the experiment.

ISAS/JAXA is studying a deployment method using centrifugal force for solar power sail mission.When a large membrane is deployed dynamically, it is twisted and vibrations are excited. Thus it is required to be deployed statically. The mechanisms for static deployment are developed. The static deployment of the square sail of diameter 20m using a high altitude balloon is demonstrated. The pre-examination on ice rink is also performed. In this paper, the contents and results of these experiments are reported in detail

ISAS/JAXA is studying a deployment method using centrifugal force for solar sail mission. The larger sail is required to be deployed statically as for actual spacecraft. We scheduled to deploy the square sail of diameter 20m using a high altitude balloon. In this paper, the mechanisms for static first and second stage deployments are proposed and developed experiment system is introduced. And the operation and results are shown in detail.

In this paper, dynamics behavior of tether retrieval with a reel mechanism in a tethered sampling method in deep space is discussed. The tethered sampling method proposed by authors is investigated as a candidate for soil sample collection method of minorbodies For the next minorbody exploration mission. The method consists of three phases: 1) shooting a corer together with a tether, 2) inserting the corer into a surface and collecting soil in the corer, 3) pulling back and retrieving the corer with the tether. This paper mainly deals with dynamics of the tether and corer in the recovery phase, and numerical simulations and fundamental experiments of the tether dynamics are conducted using a tether control mechanism. A tether tension control is proposed and tether and corer coupled dynamics are made clear by the numerical simulation. Moreover, experimental investigations are conducted by using a sampler horn and a reel mechanism which can control the tether tension and measure the tether length and velocity. The results of the experiments are compared with the results of the numerical simulation to show the feasibility of the proposed method.

Discussed in this paper are the results of the mission analysis of near Earth asteroid flyby missions using miniature Asteroid Interceptors. The Interceptor is an autonomous self-contained interplanetary probe with 10kg mass which is now under development in ISAS/JAXA. It has the capability of navigating itself autonomously to flyby the target asteroid using optical navigation system. The image of the asteroid taken by the camera onboard at the closest approach is the main science output of the mission. Firstly discussed is the mission by a single Interceptor, which enables the minimum size interplanetary mission. The interceptor is launched as a piggy back mission on a geostationary mission, separated on a geostationary transfer orbit (GTO), kicked by a solid rocket motor, and injected into an orbit suitable for encountering the asteroid. It is shown that the utilization of the Earth synchronous orbit and the Earth swing-by drastically increase the number of the possible target asteroids, which enables the selection of more scientifically interesting target for a given opportunity. The second mission concept discussed is the multiple asteroids exploration with a single launch. A straightforward application of the single Interceptor mission, that is, the mission by several independent Interceptors is shown firstly, and an option to overcome the difficulty in performing critical operation of multiple spacecrafts simultaneously is also discussed. The list of the target asteroid candidates, detailed mission sequence and maneuver parameters are shown for the assumed example mission.

This paper shows the dynamic properties interpreted about a falling cat motion. A new interpretation on non-holonomic turns was presented from coning effect point of view. It infers even the kinematics effect independent of dynamics may still drive the non-holonomic turn. However, that motion is, in this paper, proved not fully true and shown partly dependent on the inertia properties. This paper presents new interpretation findings which show the resulted non-holonomic turn may become reverse dependent on the moment of inertia ratio. This paper corrects the motion structure interpretation, in which a very interesting combination of kinematics and dynamics is found to govern the motion. And a numerical example is given for the spacecraft attitude maneuver, whose time history is explicitly described. A special feedforward control law is derived and applied to the maneuver. The results show the control strategy established well functions and enables the reorientation to be accomplished only via internal torque. What is presented does provide a comprehensive strategy widely applicable to spacecraft and space robots.

One of the most important assignments of the solar powered sail proposed in ISAS/JAXA is the static deployment of its membrane whose diameter is about 50m. The demonstration of the deployment mechanism is performed using a balloon. First, the sail shape and its folding pattern are investigated by the dynamic deployment using a spinning table. Next, the deployment motion is analyzed by numerical simulations using multi.particle model in order to decide the sail size. Finally, the experiment system is introduced and the experiment results are shown in detail.

Solar sails are the spacecraft that are propelled by sunlight. The Institute of Space and Astronautical Science (ISAS) of Japan Aerospace Exploration Agency(JAXA) has studied the solar sails which are spinning and deployed by centrifugal force. One of the technological difficulties to be realized is how to design the spanned spinning solar sails to maintain the stability while those huge membranes unfurl with deformation and oscillation. In this paper, an attention is focused on the out-of-plane oscillation and an analysis is presented about the dynamics so that the characteristic parameters are identified as for the stability of those spinning solar sails. Copyright © 2005 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

CubeSat Project is an international, educational and practical program, and many universities and companies join in the project. A CubeSat is a pico-satellite sized of 10cm^*10cm^*10cm, less than 1kg in weight, and 18 CubeSats are planned to launch at May 1 of 2002 by a Russian rocket, Dnepr. We, TITech group, are now developing a CubeSat for the launch opprtunity. The objectives of TITech CubeSat Project are design/development of pico satellite equipped with bus components under the leadership of students, and reduce the total costs by using commercial off-the-shelf (COTS) components. In this paper, we explain the design and the development schedule of TITech CubeSat.

We propose the concept of Tethered Satellite Cluster Systems. The system consists of the satellites connected by tethers,and keeps and changes the formation with active tension/length control of the tether. The purpose of the system is the saving of the thruster fuel required for the coordinated mission and the improvement of the control precision,using tether tension. The system is applied to tethered service satellites,which perform the missions,for example an autonomic inspection,casting,capture,moorage and deorbit of an uncontrolled satellite. In this paper,we treat the rotating motion; satellites rotate on the center of the mass of the system with the formation in same plane. We establish the coordinated control method using tension and thrust. This control method can decrease the fuel consumption of the thruster,for utilizing the tether tension/torque equilibriums. It can also improve the control precision. Moreover,we establish the formation control method without thrust for the transition to the objective circular motion and the system reformation. © 2001 by the American Institute of Aeronautics and Astronautics,Inc. All rights reserved.

群型テザード衛星とは, 群を形成する衛星間をアクティブに張力/長さ制御の可能なテザーで結合されたシステムであり, 今後の応用が期待されている。その概念/システム検討結果を始め, 地上実験のためのテザー制御用リール機構を含んだ模擬衛星システムを紹介する。また, 軌道上ダイナミクスの3次元シミュレーションについても言及する。

Copyright © 1997 The American Institute of Aeronautics and Astronautics Inc. All rights reserved. The dynamics of tethered systems with friction between the tethers and the bodies, as well as impact between the bodies, is investigated in this paper. A two-dimensional formulation of the dynamics between a captured spinning target and a tether with load masses at the end of the tether is presented. The tether mass is neglected but the slack in the tether is considered. Furthermore, the impacts between the tether load masses through the tether, as well as between the load mass and the target, are treated using the Lagrange impulse method. During the winding process, the dynamic and static friction between the target and the tether are considered. Numerical simulation results shed light on the complicated motion of the tether endmass and the target. The effect of tether tension control for damping the target spin is briefly discussed.