森 治

The small solar power sail demonstrator Ikaros successfully deployed its sail by a nominal sequence, which consists of two stages. However, in case of anomaly of the deployment mechanism, a one-step dynamic deployment of the sail might be employed as a contingency plan. This paper proposes a spin-up control scheme that enables the one-step deployment of Ikaros's sail, and evaluates the controlled responses using a numerical multi-particle model. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc.

The Solar Sail "IKAROS" (Interplanetary Kite-craft Accelerated by Radiation Of the Sun), which is the first solar sail on orbit, consists of 20m diagonal length square membrane made of 7.5mm thickness polyimide film. The sail membrane is deployed by centrifugal force due to spinning motion of the spacecraft. The wrapping fold is applied to realize stable deployment property. The manufacturing process of the large membrane with the folding techniques are described in detail. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc.

Japan Aerospace Exploration Agency (JAXA) launched the solar power sail orbiter "Interplanetary Kite-craft Accelerated by Radiation Of the Sun: IKAROS", on May 21st, 2010. IKRAROS was launched by H-IIA 17th vehicle with "Venus Climate Orbiter: AKATSUKI". IKAROS demonstrates a new propulsion technology of utilizing photons from the sun for deep space exploration, which is called the Solar Power Sail technology. In a case of the solar system exploration, an ion-propulsion engine is effective as a main propulsion system because it has high specific impulse and it can provide a continuous acceleration. However, the ion-engine needs high electric power in proportion to its performance. The solar power sail technology can be a hybrid engine, which can provide high electric power generated by very thin flexible solar arrays attached on the solar sail, while obtaining acceleration generated on the solar sail by the sun radiation. IKAROS succeeded in deployment the solar power sail in an interplanetary orbit, on June 9th, 2010, the first in the world, and we could obtain various flight data of the solar power sail deployment mission. We report the details of the mission system of IKAROS that applying a new deployment method, and the flight data obtained actually from IKAROS in inter-planetary orbit. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc.

Japanese spin-type solar power sail KAROS was launched in May 21 st, 2010 by JAXA, and the 20m-sized sail membrane with 7.5μm thickness was successfully deployed in last June. During the design and development process of the sail membrane structure in last three years, the nonlinear finite element elasto-dynamics code named NEDA has been improved for the prediction of the deployment motion of the sail membrane of IKAROS. The formulation of the dynamics in NEDA is based on the energy momentum method (EMM), which preserves the total energy, the linear momentum and the angular momentum. In this paper, the theory of the finite element dynamics implemented in NEDA is summarized and the mathematical model of the deployment dynamics of IKAROS is shown in detail. The numerical result is compared with the flight data, which shows the proposed numerical method is available for the prediction of the nonlinear motion of gossamer structures. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc.

Japan Exploration Agency (JAXA) launched a powered solar sail "Interplanetary Kite-craft Accelerated by Radiation Of the Sun (IKAROS)" on May 21, 2010. One of the primal technologies demonstrated at IKAROS is the deployment of the sail whose diameter is 20m class. After the launch, IKAROS performed the deployment sequence and have confirmed that the membrane was successfully expanded. In this paper, the flight data and observed dynamic motion via deployment are reported. These are compared with the results of numerical simulations using multi-particle model, and the accuracy and availability of this model is discussed. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc.

After deployment of the IKAROS solar sail in June 2010, a small ejectable camera, DCAM2, was released from the spacecraft to provide external imagery and verification of full sail deployment. In this paper we analyze the images taken by the DCAM imager and attempt to use them as a measurement source to supplement the known initial parameters to reconstruct the trajectory of the micro-spacecraft. Further complicating this analysis is the requirement that IKAROS is required to spin to maintain sail shape. Though spinning stretches the sail flat, the sail is also warped due to the solar pressure exerted upon it. The second goal of the analysis is to attempt to estimate the warping of the sail due to this pressure. The contributions of this paper cover several areas: 1) A method is provided to reconstruct the DCAM imager trajectory using a small number of photos as the sole measurement device; 2) An estimate of sail warping is provided giving some indication of total solar pressure enacted upon the sail; 3) Recommendations for the design of future external imagers of solar sails and other structures are given based on the difficulties in carrying out this analysis.

The Japan Aerospace Exploration Agency (JAXA) makes the world's first solar power sail craft IKAROS demonstration of photon propulsion and thin film solar power generation during its interplanetary cruise. The spacecraft deploys and spans a membrane of 20 meters in diameter using the spin centrifugal force. It also deploys thin film solar cells on the membrane, in order to evaluate its thermal control property and anti-radiation performance in the real operational field. The spacecraft weights approximately 310kg, launched together with the agency's Venus Climate Orbiter, AKATSUKI on May 21, 2010. This is a Front-Loading of new key technical issues of extended solar power sail mission toward Jupiter and Trojan asteroids via hybrid electric photon propulsion. This paper presents the summary of development and operation of IKAROS.

JAXA launched the world's first deep-space solar sail demonstration spacecraft "IKAROS" on May 21, 2010. IKAROS was injected to an Earth-Venus trajectory to demonstrate several key technologies for solar sail utilizing the deep space flight environment. IKAROS succeeded in deploying a 20m-span solar sail on June 9, and is now flying toward Venus with the assist of solar photon acceleration. This paper describes the mission design, system design, solar sail deployment operation and current flight status of IKAROS. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) is a small demonstration spacecraft of Solar-Sail which deploys the sail-membrane in the space to be accelerated by radiation of the sun. IKAROS has a reaction control system (RCS) to spin up itself before the centrifugal deployment of sail-membrane and control its attitude. Because of strict safety requirement, very short manufacture schedule, and relatively low manoeuvre (delta V) requirement of IKAROS, IKAROS RCS has adopted the gas-liquid equilibrium propulsion system which stores chlorofluorocarbon alternative HFC-134a as liquid-phase in the tank, extract the vapor of HFC-134a from the tank, and eject the vapor from the thruster nozzle. Cold gas through the nozzle realizes simplified thruster system, therefore can shorten manufacture schedule, but resultant 1sp is lower than that of hot gas system (ex.: Hydrazine system). However this system can achieve higher manoeuvre than cold gas system (ex.: GN2 system) because of higher density in the tank. These are why it is suitable for small satellite propulsion system. There are two major technical problems during its development. One is how to avoid the thrust degradation due to the condensation of the equilibrium gas flow in the nozzle. The other is how to extract the vapor of propellant from the tank. This paper shows the design method to solve these problems, the confirmation test results of the condensation in the nozzle, and the verification results of the vapor extracting device. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

IKAROS (Inter-planetary Kite-craft Accelerated by Radiation Of the Sun) is a Small Solar Power Sail Demonstrator which deploys the membrane and generates solar power by means of thin film solar cells. IKAROS was launched by H-IIA rocket from Tanegashima Space Center on 21st May 2010 as a piggy back spacecraft of Planet-C "AKATSUKI" Venus climate orbiter. IKAROS (and also AKATSUKI) is the first spacecraft managed by JAXA (Japan Aerospace Exploration Agency)'s system safety activity at ISAS (Institute of Space and Astronautical Science). IKAROS itself has to be managed to avoid occurring the critical hazard not only to worker, rocket and facility but also to the main spacecraft AKATSUKI because IKAROS is a piggy back spacecraft. GSE (Ground Support Equipment) and operation procedures are also objects for system safety. IKAROS has several hazardous functions like a separation mechanism, an unfolding mechanism, batteries, a pressure system and so on. There is also a problem to solve as for SCC (Stress Corrosion Cracking) of aluminium alloys used for structure material. There is three or four phase for system safety management before it is allowed to bring the spacecraft to the launch site. In this paper, it is shown that how IKAROS demonstration team manage the system safety activity, which is, the design modification, the operation management, the verification experiment for hazard control. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

This paper introduces new attitude control system for solar sail which leverages solar radiation pressure and achieves completely fuel-free and oscillation-free attitude control of flexible spinning solar sail. Novel attitude control device was developed, which is a thin film-type device and can electrically control its optical parameters such as reflectivity to generate unbalance of the solar radiation pressure applied to the edge of the sail. By using this device, minute and continuous control torque can be applied to the sail so that very stable and fuel-free attitude control of large and flexible membrane is realized. The control system was implemented as an optional attitude control system for small solar power sail demonstrator IKAROS. On-orbit attitude control experiments were conducted and the performance of the controller was successfully verified compared with the ground-based analytical performance estimation. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

JAXA launched the world's first deep-space solar sail demonstration spacecraft "IKAROS" on May 21, 2010. IKAROS was injected to an Earth-Venus trajectory to demonstrate several key technologies for solar sail utilizing the deep space flight environment. IKAROS succeeded in deploying a 20m-span solar sail on June 9, and is now flying toward Venus with the assist of solar photon acceleration. This paper describes the mission design, system design, solar sail deployment operation and current flight status of IKAROS. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

This study aims at finding structural parameters as well as control laws that enable spin-stabilized spacecraft to deploy large membranes or cable-webs in a single step. If the structures/controllers are not properly designed, the deployed elements may re-wrap around the hub after deployment, which may cause entanglement; in addition, the nutation dynamics of the system may become unacceptably large during/after the deployment. In order to develop a reliable strategy for single-step deployment, this study carries out a series of three-dimensional transient analyses of spin deployment, using a simple analytical model that allows for the nutation dynamics of the spacecraft. The analytical model consists of a rigid body and four cables with tip masses. The analysis results lead to the proposal of the structural/controller-design criteria. Finally, the applicability of the proposed design criteria is evaluated using a more practical solar sail model, in which membranes are modeled as mass-spring networks. Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Japan Aerospace Exploration Agency (JAXA) has developed the small demonstration solar sail spacecraft IKAROS (Interplanetary Kite-craft Accelerated by Radiation of the Sun), which will be launched in mid 2010. The main objective of this spacecraft is to deploy the 20m class sail membrane, and demonstrate the acceleration of a spacecraft by the solar radiation pressure (SRP) by means of that sail. It is important to model the SRP force adequately for the objective of navigation, especially for interplanetary spacecraft. In order to improve the model of the SRP torque induced by the sail membrane, the IKAROS project team plans to estimate the SRP torque parameters in orbit. In this paper, we present the approach to obtain the parameters needed for constructing the photon torque model through the analysis of the attitude dynamics.

This paper investigates the solar sail modeling and its estimation approach of solar power sail spacecraft IKAROS. Estimation of solar sail force model in space is the key factor for successful solar sail navigation because the solar sail have large uncertainty due to the flexible membrane. Since the sail wrinkles after the deployment and its surface will suffer from degradation, the solar sail force model is difficult to develop before the launch. In this paper, a practical analysis of estimating the solar sail force model from radiometric tracking data is investigated. This is demonstrated by orbit determination including parameter estimation of generalized sail model.

Dust particles which are observed as zodiacal light exist around the Earth's orbit and can create a characteristic distribution by the Earth's gravity. This paper investigates the distribution by numerical simulation on the assumption that dust particles trapped in horseshoe orbits contribute the distribution, because the orbit has the following characteristics. The velocity of a trapped dust varies by its location on the horseshoe orbit and the dust will transit with time to wider horseshoe orbit. And this paper also considers the possibility that these particles are trapped or not and reveals that the possibility depends on the dust diameter.

Asteroid probe Hayabusa was launched in May 2003 aiming for sample return from asteroid Itokawa. In the course of the mission, Hayabusa is suffering from failure of attitude control devices such as two of three reaction wheels (RWs) and chemical thrusters. As a means of precaution for an additional problem, more specifically, the last RW trouble an attitude control method which requires no RW should be considered. Ion thrusters can be utilized for attitude control by changing the direction of the thrust by two axis gimbals. In this paper, an attitude control method using only an ion thruster is proposed and the effectiveness is confirmed by numerical simulations.

The Hayabusa spacecraft embarked on its return trajectory to Earth, after its touchdown on the asteroid Itokawa. During the cruise phase Sun-pointing mode, the spin-axis of the Hayabusa performs a coning motion under the solar radiation pressure effects. The effect mainly originates from the diffuse reflection of the solar radiation pressure on the solar array panels. In the simple analysis of this coning motion, however, the diffuse reflection coefficient is inconsistent in comparison to the typical diffusive parameter of the solar array panel. This discrepancy must be clarified by constructing a more accurate model of the solar radiation pressure in order to be able to dissolve the uncertainty during the return phase of the Hayabusa spacecraft. The accurate model should also be able to support the extremely precise navigation during the return phase to the Earth. This paper presents the precise model of the solar radiation pressure of the Hayabusa spacecraft and the estimation method for obtaining the optical parameters of the solar radiation pressure model.

The Japan Aerospace Exploration Agency (JAXA) will make the world's first solar power sail craft demonstrate for both its photon propulsion and thin film solar power generation during its interplanetary cruise. The spacecraft deploys and spans its membrane of 20 meters in diameter taking the advantage of the spin centrifugal force. The spacecraft weighs approximately 315kg, launched together with the agency's Venus Climate Orbiter, PLANET-C in 2010. This will be the first actual solar sail flying an interplanetary voyage.