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.
T. Toizumi, Y. Yatsu, T. Nakamori, J. Kataoka, Y. Tsubuku, Y. Kuramoto, T. Enomoto, R. Usui, N. Kawai, K. Akiyama, S. Inagawa, H. Ashida, K. Omagari, N. Miyashita, S. Matsunaga, Y. Ishikawa, Y. Matsunaga, N. Kawabata
KEYWORDS: Avalanche photodetectors, Particles, Electrons, Satellites, Sensors, Auroras, Avalanche photodiodes, Aerospace engineering, Control systems design, Control systems
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.
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