Keisuke Yoshihara

Differential Drag as a Means of Spacecraft Formation Control

This paper investigates the feasibility of using differential drag as a means of nano-satellite formation control. Differential drag is caused when the ballistic coefficients of the spacecraft in a formation are not equal. The magnitude of differential drag depends on the difference in ballistic coefficients and also the altitude of the spacecraft formation. AGIs Satellite Tool Kit (STK) is used initially to assess the magnitude of drifts caused due to differential drag for different altitudes. This information is then used to show that it is feasible to use differential drag for spacecraft formation control. A simple PID controller is then implemented that adjusts the cross- sectional areas of the satellites such that the energies of the orbits remain equal. Results are presented that show that the control law can maintain the formation separation with reasonable accuracy.

Earth Observation Using Japanese/Canadian Formation Flying Nanosatellites

Japan Canada Joint Collaboration Satellites (JC2Sat) is a joint project between the Canadian Space Agency (CSA) and the Japan Aerospace Exploration Agency (JAXA). The main objective of the project is to design, build, launch and operate two 18 kg nearly identical nanosatellites that will be launched as a stack and separated in space to demonstrate the feasibility of Autonomous Formation Flight (AFF) based on aerodynamic differential drag only. The specific configuration of the JC2Sat nanosatellites serves as an ideal technology demonstration platform for the Miniature far Infra-Red Radiometer (Mirad) instrument developed jointly by CSA and Institut National d’Optique (INO). Each nanosatellite carries a Mirad instrument for the purpose of Earth’s limb sounding. Based on un-cooled far infrared micro-bolometers, these low mass and low power payloads will co-register the limb profiles in the emission bands of greenhouse gases CO2 and H2O, respectively centered at wavelengths of 15 and 25 μm. The development of JC2Sat is carried out by a united small team consisting of engineers and researchers from both CSA and JAXA. JC2Sat is planned to be ready for launch in 2011. Mission duration is defined to be one year. At the time of writing, the project is in phase C.

Development of Attitude Control System of Micro LabSat

Abstract Micro LabSat is a 50(kg) class micro satellite that was launched on December 14, 2002. Micro LabSat switches attitude control modes according to the operation mode. In the nominal operation mode, spin-stabilized control is used. In the mission mode, three axis control is used. Micro LabSat carries only simple low cost sensors for attitude determination. This paper describes design and development of the Micro LabSat attitude control system.

On-Orbit Experiment of Motion Estimation and Tracking of Tumbling Object in Space

Abstract Capture of tumbling objects in space will be one of important on-orbit service technologies in future. It requires a series of technologies such as camera-image tracking of the target, target attitude motion estimation, and attitude control of the chaser to approach and grasp the target. Based on the theoretical and simulation-based research, University of Tokyo successfully performed on-orbit experiment of some of these technologies on a NASDAs (currently JAXAs) microsatellite named “µ-LABSAT.” In this paper, the objectives and procedure of these experiments, the control and estimation algorithms and the results will be described.