Mechanism-free control method of solar/thermal radiation pressure for application to attitude control
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		    https://doi.org/10.1007/s42064-019-0062-0
 
 Mechanism-free control method of solar/thermal radiation pressure for application to attitude control Toshihiro Chujo1 (), Motoki Watanabe2 , and Osamu Mori3 1. Tokyo Institute of Technology, Tokyo, 152-8550, Japan 2. Aoyama Gakuin University, Sagamihara, 252-5258, Japan 3. Japan Aerospace Exploration Agency, Sagamihara, 252-5210, Japan
 
 ABSTRACT Solar radiation pressure (SRP) impinging on spacecraft is usually regarded as a disturbance for attitude motion, but it can be harnessed to solve the very problem it creates. Active SRP control is possible with solar radiation powered thin-film devices such as reflectivity control devices or liquid crystal devices with reflective microstructure. Thermal radiation
 
 KEYWORDS solar radiation pressure (SRP) thermal radiation pressure (TRP)
 
 pressure (TRP) can likewise be used to solve flight attitude problems caused by SRP, TRP,
 
 attitude control
 
 or other factors. TRP on solar cells can be controlled by switching regulators under the
 
 solar sail
 
 control of them, resulting in temperature change. These SRP/TRP controls are free from mechanisms, such as reaction wheels, and thus they do not produce internal disturbances. In addition, the magnitude of SRP/TRP torques is generally much smaller than internal disturbance torques produced by reaction wheels, which creates a potential for precision far
 
 Research Article
 
 beyond that achieved with mechanical controls. This paper summarizes how SRP/TRP can
 
 Received: 2 May 2019
 
 be used by means of numerical simulations of typical control methods. The usefulness of this
 
 Accepted: 14 June 2019
 
 mechanism-free attitude control is verified for future use on both Earth orbiting satellites
 
 © Tsinghua University Press
 
 and interplanetary spacecraft including solar sails.
 
 1
 
 Introduction
 
 Solar radiation pressure (SRP) is usually regarded as a disturbance for attitude motion of spacecraft, but recently, it is being used to correct attitude motion problems. Although the magnitude of SRP is small (4.6 × 10−6 N/m2 for a surface absorbing all sunlight energy at 1 AU), if the impulse accumulates for significant amount of time, it generates enough accumulated torque impulse to drastically change the attitude of a spacecraft. A typical example of SRP control for attitude control was seen in the Interplanetary Kitecraft Accelerated by Radiation Of the Sun (IKAROS) mission [1, 2], which was launched in 2010 by JAXA and demonstrated the solar-sail technology for the first time. IKAROS was equipped with thin-film devices (RCDs) on the sail membrane that were composed of polyimide-films and liquid crystal and thus could electrically modify the optical properties of the surface [3].
 
 
 
 [email protected]
 
 2019
 
 When the device is switched on, specular reflection is dominant, while when it is off, diffusive reflection is dominant, which changes the magnitude of SRP impinging on the surface. IKAROS was equipped with many of them and it was shown that they could create an SRP imbalance by the on/off distribution. IKAR		
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