This paper discusses about attitude dynamics for spinning spacecraft under influence of solar radiation pressure(SRP). Generally spinning objects maintain its spin axis with reference to inertial frame. But if disturbance torquelike SRP affects this object, the spinning motion indicates a unique behavior due to dynamical coupling between theSRP torque and the spin motion. IKAROS and HAYABUSA launched by Japan Aerospace Exploration Agency(JAXA) positively utilize this phenomenon in actual operation. For example, HAYABUSA was kept sun-orientedduring spin stabilized phases without fuel utilizing this effect. In the IKAROS mission a method has been developedwhich controls both attitude and orbital trajectory by SRP. These two are the remarkable examples of how SRP isutilized for fuel-saving and efficient operation. To enable to this technique, it is essential to understand attitudedynamics including SRP influence correctly.In past papers, simplified attitude models including SRP effect are derived both for HAYABUSA and IKAROSmissions. These models are cable of explain wide range attitude motions. But in the flight data of HAYABUSA andIKAROS, there are remarkable motions that these simplified models cannot explain. In past papers, these motionscalled wind mill effect and spiral behavior. There are two purposes in this paper. The one is alignment ofmicroscopic theory and macroscopic theory. The other one is considering these remarkable motions theoretically.For these purposes, we construct FEM model including SRP effects and simulate attitude dynamics numerically. Inthe results of simulations, two causes were found. The one is optical property of surface. The other one is non-flatsurface effect of spacecraft. In this paper, we indicate the background of constructing SRP model and the evaluationincluding flight data of HAYABUSA and IKAROS. Then we discuss about the relationship between simplifiedattitude models and microscopic models.
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