System

The arrangement of instruments is shown in Fig.1. The idea of central pillar configuration inherited the design concept of previous satellite SPRITE-SAT. The panel of central pillar is 3-mm aluminum alloy, and 6 side panels are aluminum grid with 10-mm thickness ribs and 1.5-mm thickness skins. The solar cells are pasted in 5 panels except a bottom panel.

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Fig.1 Internal structure image

The system specifications are listed in Table 1, and the subsystems relationship diagram is shown in Fig.2. The controller units of SCU, ACU, PCU, and SHU are including a commercial CPU, and an antifuse or flush FPGA, and the science mission instruments are connected to SHU.

Table 1 System specifications
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Fig.2 System diagram of bus units

For the ground operation, Tohoku University Ground Station is used as a primary operation station. As a receive-only station, the ground stations in Sweden (2.4-m diameter) and Fukui University of Technology (10-m diameter) are also used. At the bitrates of 38400 bps, the size of data will be 7.96 MB/day using Japanese single station which can observe a satellite in 4 pass/day. Adding a station in Sweden, the size increases to 27.8 MB/day in 14 pass/day. If the station of FUT can receive a data in about 100 kbps (96000 bps), the size achieves 39.8 MB/day.

The procedure of attitude control is shown in Fig.3. The angular velocity just after satellite separation will be about 2.3 deg/s from the result of SPRITE-SAT. The spin motion can be decreased into 0.2 deg/s by the detumbling control using magnetometers and magnetic torquers. After the Observation Mode is started, which span is 15 minutes in sunshine and 15 minutes in eclipse, the satellite measures the attitude by star sensors and gyro sensors, and rotates the attitude to the target direction by using reaction wheels. It keeps the fine pointing control until the end of Observation Mode.

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Fig.3 Outline of attitude control

(C) The Space Robotics Lab (Space Exploration Lab), Tohoku University
Last-modified: 2011-06-16 (Thu) 08:37:50 (2870d)