Shinichi Nakasuka

Attitude control system for the nano‐astrometry satellite “Nano‐JASMINE”

Purpose – This paper aims to present an attitude determination and control system for a nano‐astrometry satellite which requires precise angular rate control. Focus of the research is methods to achieve the requirement.Design/methodology/approach – In order to obtain astrometry data, the satellite attitude should be controlled to an accuracy of 0.05°. Furthermore, attitude spin rate must be controlled to an accuracy of 4×10−7 rad/s during observation. In this paper the following unique ideas to achieve these requirements are introduced: magnetic disturbance compensation and rate estimation using star blurred images.Findings – This paper presents the feasibility of a high accurate attitude control system in nano‐ and micro‐satellite missions.Practical implications – This paper presents a possibility of the application of nano‐satellites to remote‐sensing and astronomy mission, which requires accurate attitude control.Originality/value – Originalities of the paper are the methods to achieve the high accurat...

REMOTE SENSING BY UNIVERSITY OF TOKYO’S PICO-SATELLITE PROJECT “PRISM”

This paper presents our design concept and some technological topics in our ongoing project, “PRISM” which stands for “Pico-satellite for Remote-sensing and Innovative Space Missions”. Nakasuka laboratory in University of Tokyo has been designing and developing this pico-satellite since 2002. Its main mission is remote sensing. Basically, we aim to obtain Earth images with as high resolution as about 30 meters by its compact spacecraft bus, which is a 17cm*17cm*25cm and will be weigh less than 5kg. PRISM has a refracting optical system using one group of lenses, unlike most of the Earth Observation satellites. A main reason why we adopted this kind of optics is the possibility of downsizing the whole optics with extensible tube framework for telescope. Moreover, we’ve been dedicated to design and development of many components in every subsystem. The fundamentals of its bus technologies are on the basis of the experience in our previous project, “CubeSat XI” [sai] [1], which was launched in 2003 and has been operative for more than 16 months. We are now developing PRISM engineering model with a hope to launch its flight model between 2005 and 2006.

TARGET ATTITUDE MOTION ESTIMATION AND TRACKING EXPERIMENT ON MICRO-SATELLITE "MICRO-LABSAT"

On a NASDA’s microsatellite named “μ-LABSAT,” which was launched by H-IIA on December 14, 2002 (Fig.1), Communications Research Laboratory (CRL), National Aerospace Laboratory (NAL) and University of Tokyo (UT) have been jointly performing several orbital experiments as technology demonstration towards the future orbital servicing missions. In University of Tokyo’s experiment which was held on May 14, 2003, the micro-satellite released a small object named “target,” and its rotational motion was estimated by the images captured continually using a camera developed by CRL. Then satellite attitude control was performed by visual feedbacks of the target image position on the camera frame so that the target image may come to a certain point on the camera frame. This is a pre-experiment of so-called LOS (Line Of Sight) control, which will be indispensable during rendezvous and docking to the satellite to be serviced. In this paper, the objectives and procedure of these experiments, and the results will be described. 54th International Astronautical Congress of the International Astronautical Federation, the International Academy of Astronautics, and the International Institute of Space Law 29 September 3 October 2003, Bremen, Germany IAC-03-A.P.06 Copyright

Low-Thrust Trajectory Optimization Method Considering Stochastic Operational Anomaly

This study aims to optimize a low-thrust trajectory for spacecraft in the event of stochastic operational anomaly. Most of the recent study have focused on the deterministic trajectory optimization for preliminary mission design. In the low-thrust operation, which conventionally use empirical (nonoptimum) operation strategies, the duty cycle of low-thrust propulsion is imposed throughout the trajectory. This paper presents the optimum value of duty cycle in the each operation cycle using Lagrange multiplier. The result shows that constant duty cycle constraint is optimal solution if surplus coasting period in the unit operation cycle is not used as thrusting period; in other words, the constant duty cycle throughout the thrust arc is not always optimum strategy if surplus coasting period is intensively used at the end of thrusting arc. Numerical example shows that the solution calculated numerically corresponds to the theoretical solution.