Experimental Study for Synthetic Aperture Telescope Using Formation Flying Micro-Satellites for High-Frequency and High-Resolution GEO Remote Sensing

Earth remote sensing from geostationary orbit (GEO) realizes high time resolution that is essential for disaster monitoring; however, the spatial resolution is commonly worse than observation from low Earth orbit. In order to achieve high-resolution and high-frequency GEO remote sensing, we have proposed a “Formation Flying Synthetic Aperture Telescope (FFSAT)” with multiple micro-satellites. The FFSAT can improve the spatial resolution by using the technique of a synthetic aperture, and therefore the relative positions and attitudes between the optical units of each satellite must be controlled with an accuracy better than 1/10 of the observation wavelength. In order to verify feasibility of such highly accurate control, the characteristics of sensors and actuators which are essential for an ultra-high-accuracy formation flying were numerically modeled. We consider control laws for keeping the relative position and attitude of the μm-class formation flying using the high-precision simulator built on the numerical models. In addition, the cooperative control of the piezo stages and the thrusters is studied to reduce the fuel consumption of the FFSAT system. The simulation results made the FFSAT mission more feasible

University of Tokyo\u27s CubeSat Project: Its Educational and Technological Significance

This paper describes outline of the University of Tokyo Intelligent Space Systems Laboratory(ISSL)\u27s CubeSat \XI for the demonstration of the pico-satellite bus technology and validation of the commercial- o_-the-shelf parts in space as well as the earth imaging mission. CubeSat project is the international joint program, which aims for developing and actually launching 10cm cubic satellites weighing less than 1kg to the earth\u27s orbit. 18 CubeSats developed by Japanese and U.S. institutes are to be launched by the Russian launch vehicle \Dnepr in May, 2002 to the Sun-synchronized orbit. The project in ISSL is conducted by 20 space engineering students as a material of education

On-Orbit Verification of Luminance Based Target Tracking and Faint Body Extractions by a Small Telescope on the World\u27s First Micro-Interplanetary Space Probe

In recent years, low cost and quick development of very small satellites ranging from CubeSats of 1 kg to micro-satellites of approximately 50 kg have allowed advances in space development and application. Although most of these satellites are in Earth orbits, a small spacecraft for deep-space missions has been developed and launched for the first time in the world. The Proximate Object Close Flyby with Optical Navigation (PROCYON) micro-interplanetary spacecraft, developed by the University of Tokyo and the Japan Aerospace Exploration Agency, was launched in December 2014 as one of the secondary payloads of the asteroid sample return spacecraft Hayabusa-2. The main mission of PROCYON is to demonstrate critical technologies of 50-kg-class interplanetary spacecraft exploration such as communication, attitude control, thermal control, and power generation. Furthermore, advanced missions of PROCYON enable a close flyby of an asteroid at an altitude of approximately several dozen kilometers and the capture of high-resolution images of approximately several meters per pixel by a telescope. In the flyby missions, the change of the target direction vector from the spacecraft to the asteroid is steeper than that of past flyby interplanetary probes. Thus, the spacecraft could not keep the asteroid in a telescope\u27s field of view only by performing an attitude maneuver of the entire body. To overcome this attitude maneuverability problem, a small and line-of-sight controllable telescope using a rotating mirror was developed and implemented on PROCYON. Due to the system constraint of the micro-spacecraft, this telescope should also be used for optical navigation by the faint asteroid images performed before several days of closest approach. The telescope is very lightweight, approximately 680 g. Moreover, its exposure time range is very high; thus, it can capture images of very dark astronomical bodies of approximately 12 magnitudes to supply information for trajectory correction maneuvers as well as bright bodies observed at a short distance during the close flyby. The results of experiments in the interplanetary orbit are shown in the presentation. Several 12 magnitude stars were identified from the images captured in orbit by utilizing the noise reduction techniques. This result complies with mission requirement of the optical navigation of PROCYON to extract the target images at least three days before closest approach. During the Earth approaching period, a visual feedback tracking experiment was performed utilizing the reflected light from the Earth. Time history of the rotation angle of the telescope shows the direction determination accuracy of the target body by the luminance center extraction using on-board image processing system. The know-how of the optical system of PROCYON enables a variety of missions in the interplanetary field performed by micro-spacecraft