Tatsuaki Hashimoto

A novel method for micro-gravity experiments using high altitude balloon is now under development in JAXA. The notable feature of this system is its double-shell structure. Dropped from the high altitude balloon, the inner shell falls freely for 30 to 60 seconds because the outer shell is controlled not to collide with the inner shell. Sixteen number of cold gas thrusters are installed on the vehicle to control not only its falling attitude but also spacing between the inner shell and the outer shell. This paper presents design strategy and verifi cation test results of the 50 N cold gas thrusters developed for this micro gravity experimental system. The preliminary results of the fl ight test are also presented to show its feasibility.

For future advanced Earth observation or astronomy missions, an inertial reference unit (IRU) having high accuracy, a wide dynamic range, a long useful lifetime, and high reliability is required. The fiber optic gyro (FOG) is a strong candidate to fulfill those requirements: it has already been applied widely to satellites. We have been developing a high-performance FOG inertial reference unit (FOG-IRU) for use in future satellites. This paper describes the architecture and design results of the FOG-IRU. In addition, it presents a summary of performance test results and analyses of gyros' critical items: angle random walk, scale factor, and bias repeatability.

Recently, the missions of the earth observation or space science satellites are becoming more demanding and so are the attitude control requirements. For this reason, not only reducing the induced vibrations of onboard instruments but also active vibration suppression is required In the previous research works, a Magnetic Bearing Wheel (MBW) is expected to be a low disturbance wheel with proper gimbals control. The objective of this study is to use MBW as active vibration suppression of other instruments at the mission instrument position. To achieve this objective, accelerators and vibrator are established on the sham satellite panel, and the experiment is made to suppress vibrator disturbance in accelerator positions by controlling MBW parameters. In this paper, the experiment way and results are reported.

The microgravity experimental system that uses the high altitude balloon is now developed in ISAS/JAXA. This experimental method is, 1) Experiment body is raised to 40km altitude by the high altitude balloon, 2) The experimental system is separated, 3) A free fall for 30-40 seconds is achieved. In the experiment, the experiment body enters a supersonic state when the free fall time exceeds about 30 seconds. Therefore, it can be expected that the body offers a supersonic flight environment besides the microgravity experiment. In this paper, explanation of microgravity experiment was shown, and supersonic flight by mounting engine was considered.

This paper discusses on control law for Balloon Based Micro-Gravity Experimental Vehicle. The vehicle is carried up to an altitude of 40km by a balloon and released. During the free fall, micro-gravity environment is provided in a spherical laboratory floating in the vehicle. Gas jet thrusters control the vehicle to keep the clearance between the laboratory and the inner wall of vehicle. This paper proposes new thruster distribution law, which reduces the fuel consumption without increasing of attitude error. Flight experiment has been carried out successfully in May, 2007. This paper also reports the results.