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Tsubame is a university-built small satellite mission to measure polarization of hard X-ray photons (30–200 keV) from gamma-ray bursts (GRB) using azimuthal angle anisotropy of Compton-scattered photons. Polarimetry in the hard X-ray and soft gamma-ray band should play a crucial role in understanding of high energy emission mechanisms, the distribution of magnetic fields and radiation fields of gamma-ray bursts. Tsubame has two instruments: the Wide-field Bust Monitor (WBM) and the Hard X-ray Compton Polarimeter (HXCP). The WBM detects a burst and determines on board the direction of the burst occurrence with an accuracy of 10°. The spacecraft is then slewed to point the GRB within 15 s from the WBM trigger using the Control Moment Gyro (CMG), a high speed attitude control device. HXCP will measure the polarized X-ray photons from the GRB while the spacecraft spins slowly around the bore sight. In this paper, we present an overview of the Tsubame mission, the results of a test experiment for HXCP using a polarized hard X-ray beam, and its comparison with a Monte Carlo simulation.

In this paper, on-orbit joint flexibility experiments using ETS-VII (Engineering Test Satellite VII) robotic arm are discussed. Considering manipulability of the robotic arm, the arm vibration due to the joint stiffness may influence on the berthing manipulation. The vibration of the robotic arm mounted on a satellite is characterized as follows, 1) coupling between the arm and the satellite attitude vibration, and 2) transition of the arm natural frequency according to its posture changes with the inertial parameter variation. The experiments are planned to evaluate these vibration disturbance. Using telemetry data detected by FTS (Force Torque Sensor) attached to the end-effector, the arm natural frequencies and the transitions of the arm vibration amplitude are analyzed. And the validity of the simulation results is demonstrated.

Gamma-ray bursts (GRBs) are the most drastic and intriguing phenomena in high energy astrophysics. The nature of relativistic collimated outflows that bight be generated by gravitational collapses of massive stars is to investigate the physical process just around the central engines by constraining magnetic environment. For this purpose we developed a compact and high sensitive hard x-ray polarimeter aboard a university class micro-satellite "TSUBAME." Unsurprisingly, any micro-satellites have stringent limitations on size, mass, and power consumption restricting the effective area of detectors. However, high luminosities of GRBs allow us to measure their polarizations only if we start observations just after the ignitions. TSUBAME overcomes this problem by using compact an high-torque actuators, control moment gyroscopes, that enable high speed attitude control faster than 6° s -1 . Cooperating with a wide field burst monitor on board for real time position determination of GRBs, TSUBAME can start a pointing observation within ~15 s after the detection for any GRBs in the half-sky field of view of the burst monitor.

ecently, a variety of solar sail spacecrafts using thin large membranes have been developed in US, Europe and Japan. In Japan, centrifugally deployed solar sails have been mainly investigated 1 . A solar power sail demonstration spacecraft “IKAROS” was developed by Japan Aerospace Exploration Agency and was launched on May 21th, 2010 by H-IIA launch vehicle. 2,3 Figure 1 shows an overview of “IKAROS” in space. The square solar sail with 20 meters in diagonal and 7.5 micrometers in thickness was successfully deployed by centrifugal force using no extendable booms. The sail consists of four trapezoidal petals which were folded up into strips and rolled up around the spacecraft in stowed configuration. The deployment of the membrane consists of two stages. In the first stage, the strips are quasistatically reeled out. In the second stage, the strips are dynamically unfurled. Since on-ground dynamic deployment experiments of the large membrane are impossible, small-scale experiments and numerical simulations are necessary to predict the deployment dynamics. In this paper, a deployment experiment of a smallscale square membrane similar to “IKAROS” is conducted in a vacuum chamber and corresponding numerical simulations are performed by employing a spring-mass system model. The deployment behavior is discussed and the results of the experiment and simulations are compared to examine the validity of the simulations.

1 Post-doctoral Researcher, JAXA Space Exploration Center, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa, Japan. 2 Assistant Professor, JAXA Space Exploration Center, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa, Japan. 3 Professor, Department of Aerospace Engineering, 7-24-1 Narashinodai, Funabashi, Chiba, Japan. 4 Assistant Professor, Department of Mechanical and Aerospace Engineering, 2-12-1 Ookayama, Meguro-ku, Tokyo, Japan. 5 Graduate Student, Department of Aeronautics and Astronautics, 4-1-1 Kitakaname, Hiratsuka, Kanagawa, Japan. 6 Assistant Professor, Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa, Japan. 7 Post-doctoral Fellow, JAXA Space Exploration Center, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa, Japan. 8 Associate Professor, Department of Built Environment, 4259-G3-6, Nagatsuta, Midori-ku, Yokohama, Japan. 9 Associate Professor, Department of Mechanical and Aerospace Engineering, 2-12-1 Ookayama, Meguro-ku, Tokyo, Japan. 10 Visiting Professor, Faculty of Science and Engineering, 55S-608, 3-4-1 Okubo, Shinjyuku, Tokyo, Japan. 11 Professor, JAXA Space Exploration Center, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa, Japan. 52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference 19th 4 7 April 2011, Denver, Colorado AIAA 2011-1890

Cute-1.7+APD II is the third pico-satellite developed by students at the Tokyo Institute of Technology. One of the primary goals of the mission is to validate the use of avalanche photodiodes (APDs) as a radiation detector for the first time in a space experiment. The satellite was successfully launched by an ISRO PSLV-C9 rocket in Apr 2008 and has since been in operation for more than 20 months. Cute-1.7+APD II carries two reversetype APDs to monitor the distribution of low energy particles down to 9.2 keV trapped in a Low Earth Orbit (LEO), including South Atlantic Anomaly (SAA) as well as aurora bands. We present the design parameters and various preflight tests of the APDs prior to launch, particularly, the high counting response and active gain control system for the Cute-1.7+APD II mission. Examples of electron/proton distribution, obtained in continuous 12-hour observations, will be presented to demonstrate the initial flight performance of the APDs in orbit.

[1] The Cute-1.7+APD II, 10 × 15 × 20 cm3 in size and 5 kg in mass, is the third picosatellite developed by students at the Tokyo Institute of Technology. One of the primary goals of the Cute-1.7+APD II mission is to validate the use of avalanche photodiodes (APDs) as a radiation detector for the first time in a space experiment. While the mission itself is immature compared to the forefront satellites of space plasma physics, use of APDs offers various possibilities regarding a brand-new electron energy analyzer for medium-energy electrons and ions (1–100 keV), as well as a high-performance light sensor for the future X-ray astronomy missions. The satellite was successfully launched by ISRO PSLV-C9 rocket on 28 April 2008 and has since been in operation for more than a year. The Cute-1.7+APD II carries two reverse-type APDs to monitor the distribution of low-energy particles (mainly electrons and protons) down to 9.2 keV trapped in a low Earth orbit (LEO), including the South Atlantic Anomaly (SAA) as well as aurora bands. We present the design parameters and various preflight tests of the APDs prior to launch, particularly, the high counting response and active gain control system for the Cute-1.7+APD II mission. Examples of electron/proton distribution, obtained in continuous 12 h observations, will be presented to demonstrate the initial flight performance of the APDs in orbit.

Hard X-ray polarization is believed to be one of the most promising methods to investigate the physical processes just around the central engines by constraining the magnetic environment. For this purpose we are now developing a compact and highly sensitive hard X-ray polarimeter aboard a university class micro-satellite “TSUBAME”. We are now developing the flight model of the satellite aiming for the launch in late 2012 from Russia.

“TSUBAME” is a university-built small satellite mission to measure polarization of hard X-ray photons (30-200 keV) from gamma-ray bursts (GRBs) using azimuthal anisotropy of Compton-scattered photons. Polarimetry in the hard X-ray and soft γ-ray bands should provide crucial information for understanding the high-energy emission mechanisms and the distribution of magnetic fields and radiation fields in the astrophysical sources. TSUBAME has two instruments: the Wide-field Burst Monitor (WBM) and the Hard X-ray Compton Polarimeter (HXCP). The WBM determines on board the direction of the burst occurrence with an accuracy of 10 degrees, then using a high speed attitude control device, the HXCP is pointed to the GRB within 15 seconds after the burst occurrence to promptly detect polarized X-ray photons from the GRB. We present an overview of the TSUBAME mission, its estimated scientific capability for detecting GRBs and measuring their X-ray polarization, development of multi-anode photomultiplier tubes that use ultra bi-alkali photocathodes, and the future plans of this mission.

The Cute-1.7 was launched successfully in February 2006 as a piggyback satellite of the Astro-F mission. The Cute-1.7 dimensions are 10 × 10 × 20 cm 3 box with a total mass of 3.6 kg. It is the second pico-satellite to have been developed completely by students of the Tokyo Institute of Technology (Tokyo Tech.) after the successful launch of the CUTE-I in June 2003. The goals of the Cute-1.7 mission are two-fold: (1) to validate high-performance, commercially available products for the first time in space. We particularly use personal digital assistants (PDAs) as a main computer in orbit (2) to demonstrate new potential uses for small satellites in various space studies, as proposed by the “satellite-core” concept. For the Cute-1.7 mission, we will carry avalanche photo diodes (APDs) as a high-count particle monitor in low-Earth orbit. Here we present details of various ground tests and pre-flight performance of the Cute-1.7 immediately before the launch. Results of the Cute-1.7 mission will provide quick feedback for space applications of APDs in Japan's future X-ray astronomy mission NeXT.