1) Tohoku University, Japan 2) National Institute of Information and Communication Technology, Japan

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1 Toshinori Kuwahara 1) *, Kazuya Yoshida 1), Yoshihiro Tomioka 1), Kazufumi Fukuda 1), Hiroo Kunimori 2), Morio Toyoshima 2), Tetsuharu Fuse 2), Toshihiro Kubooka 2) 1) Tohoku University, Japan 2) National Institute of Information and Communication Technology, Japan August 12,

2 Micro-satellite Development Activity in Japan Micro-satellite missions planned in 2013 H-IIA Piggyback (ALOS-2) SPROUT: Nihon University RISING-2: Tohoku University UNIFORM-1: Wakayama University SOCRATES: AES Co., Ltd. H-IIA Piggyback (GPM) STARS-II: Kagawa University TeikyoSat-3: Teikyo University ShindaiSat: Shinsyu University KSAT2: Kagoshima University INVADER: Tama Art University OPUSAT: Osaka Prefecture University ITF-1: University of Tsukuba Others Several 50kg-class microsatellites JAXA 2

3 Micro-satellite Development at SRL SPRITE-SAT (44kg) #1:SPRITE-SAT (RISING-1) Launch: Jan (H-IIA) Demonstration of JAXA Image acquisitions by mission camera RISING-2 (42kg) Coarse attitude control Deployment of the boom #2:RISING-2 FM ready. Launch in 2013 (H-IIA) Mission Multi-spectrum observation with a Liquid Crystal Tunable Filter ( nm) RAIKO (2.6kg) High resolution stereo images of cumulonimbus Terrestrial luminous events in upper atmosphere #3:RAIKO Launch: July 2012 (H-IIB) (Deployment from the ISS: Oct. 2012) Mission RISESAT (55kg) Technology demonstrations (Communication URX, S, Ku, Image acquisition, De-orbit) #4:RISESAT Launch (2013 ~) Mission International Scientific Missions Satellite-to-ground laser communication 3

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5 RAIKO Deployment: Oct. 4, 2012 Re-entry: Aug. 5,

6 RISESAT Project Background Hodoyoshi Program (Professor Nakasuka, The University of Tokyo) Development of five 50kg class micro-satellites One of the satellites is an international scientific micro-satellite (RISESAT) RISESAT also has some technology demonstration missions. RISESAT: Rapid International Scientific Experiment Satellite Mission Objectives Demonstrate international scientific missions by inviting instruments from abroad Investigation on advanced bus system technologies for future scientific microsatellites Development of a reliable, robust and cost effective micro-satellite bus system Expected effects Realization of mechanism of rapid demonstration of scientific missions in the future Improvement of microsatellite technologies which enables future challenging scientific missions Commercial spin-off of providing cost-effective microsatellite bus systems 6

7 RISESAT System Specifications Launch configuration After panel deployment 7

8 Payload Instruments Camera Instruments Sensor Instruments High Precision Telescope - HPT (Taiwan(NCU)) Meteor counter - DOTCam (Taiwan(NCKU)) TriTel 3D Dosimeter (Hungary) TIMEPIX Particle counter (Czech) Ocean Observation Camera - OOC (Hokkaido University) Technology Demonstration Laser Communication Transmitter VSOTA (NICT, Japan) MEMS Magnetometer (Sweden) 8

9 Optical Communication with VSOTA (1) Collaborative research between National Institute of Information and Communication Technology (NICT) and Tohoku University VSOTA: Very Small Optical Transmitter for Component Validation Objectives: Satellite-to-Ground Data Downlink demonstration for future realization of G-bit optical data downlink Future alternative for RF communication on micro-satellite no frequency allocation problem Dual-band: 980 nm 1540 nm Installation: Fixed to sat. body. Attitude control: Target pointing mode Bit rate: 100Kbps~ 9

10 Optical Communication with VSOTA (2) RISESAT (60kg) Tohoku University - NICT SOCRATES (50kg)* Advanced Engineering Services Co., Ltd - NICT Laser Terminal VSOTA SOTA Downlink 980nm 1550nm 980nm 1550nm Pilot signal detector none 1060nm Pointing Mechanism Satellite s Attitude Control! Coarse (Mechanical Gimbals) + Fine Pointing Mechanism Bit Rate 100Kbps ~ 10Mbps 1Mbps/10Mbps Satellite Attitude Control Accuracy Better than 0.1 deg down to 0.04 deg and more. unknown mass ~1kg ~6kg *Hideki Takenaka, et al., Experiment plan for a small optical transponder onboard a 50kg-class small satellite," 2011 International Conference on Space Optical Systems and Applications, Santa Monica, May 11-13, Hideki Takenaka, et. Al., Experiment plan for Space Communications Research Advanced Technology Satellite," IEICE Technical Report,

11 Laser Transmitter: VSOTA VSOTA: Very Small Optical Transmitter for Component Validation VSOTA-COL: Collimator Assembly VSOTA-E: Laser diode driver electronics VSOTA-CNT: Electrical controller of VSOTA-E. Space Plug-&-Play Avionics Compatible VSOTA-COL NICT SHU 11

12 Mechanical Configuration Launcher Interface Payload Segment 12

13 System Architecture Telemetry, Tracking & Command Command & Data Handling Orbit determination New Development [UHYB] UHF antenna hybrid [URX] UHF receiver [STX] S-band transmitter [DOM] De-orbit Mechanism [SPDM] Solar Panel Depl. Mech. [BAT] Battery unit Power Supply System [DPD] Data Decoder [TTR] Telecommand, telemetry, and recovery [PCU] Power control unit [SCP] Solar cells [SCU] Satellite central unit [CPU-N] Processor unit (nominal) [CTR] Command and telemetry router [CPU-R] Processor unit (redundant) Coarse Attitude Control System [GPSR] GPS receiver [MTQ] Magnetic Torquers (3-axes) [GAS] Geomagnetic Sensor (3-axes) [SAS] Coarse sun sensors Payload Re-design Fine Attitude Control System [ACU] Attitude Control Unit [RW] Reaction wheels (4) [STT] Star Trackers (2) [FOG] Gyroscope (3-axes) [SES] Sun earth sensors (4) [XTX] X-band transmitter Coder [SHU] Science handling unit [MMC] Micro monitor camera Main Bus Com. Line Scientific Data Line Power Line High-speed Downlink 5R1_2012/02/07 Pay 1 NCU/FPTI Pay 2 NCKU Pay 3 OOC Pay 4 MTA EK Pay 5 IEAP Pay 6 ASTC Laser Link Terminal VSOTA Other General Lines Main computing unit Antifuse FPGA

14 Attitude Control Error Budget Ground Measurement GPS signal real-time processing ACS 14

15 Coarse Control Fine Control Magnetometer (1 x 3 axes) STT (2) Magnetic Torquers (3 axes) GPS (1) FOG (1 x 3 axes) Fine Sun Sensor (4) Coarse Sun Sensor (8) RW (4) 15

16 Attitude Control Modes Detumbling Mode ω < 0.5 º/s ω 5 º/s Spin-stabilization Safe Mode TC TC Coarse Pointing Fine Pointing ω 5 º/s /Contingency Level 2 ω 5 º/s /Contingency Level 2 Coarse Sun Pointing Mode TC Fine Sun Pointing Mode TC TC TC Satellite controls its attitude to point the (laser) direction toward an optical ground station during fly-over Mission Operation Nadir Pointing Mode TC TC TC TC Inertial Pointing Mode Target Pointing Mode 16

17 Attitude Control: Target Pointing Mode Collimators are mechanically fixed to satellite structure (bottom) Satellite controls its attitude to point the laser direction toward an optical ground station during flyover Required control accuracy: 0.4 deg (3σ) for 100 Kbps Simulation results illustrate good feasibility. Ground verification is ongoing. ACU(H/W)-in-the-loop (handshake) 17

18 On-going Improvement of Attitude Control Accuracy GPS real-time position estimation Extended Kalman Filter for realtime/forward position estimation. Attitude filter EKF Extended Kalman Filter for sensor fusion between Star Trackers and FOG for real-time/forward attitude estimation. HPT as guidance sensor HPT/LCTF is being modified to be used for fine-guidance sensor in closed-loop control. (pilot laser beam from G.S.) Ground testing Dynamic closed-loop simulation/evaluation environment. 18

19 Conclusion and outlook Micro-satellite RISESAT demonstrates satellite-to-ground dualband laser communication on micro-satellite. The pointing of laser beams are achieved purely based on satellite attitude control. RISESAT carries dual-band laser communication transmitter developed by NICT. RISESAT is capable of target pointing attitude control for optical link between ground stations. The RISESAT system is now under development. The flight model will be ready by early Combination of RISESAT s attitude control capability and the fine pointing mechanism in the future will allow light-weight G-bit optical communication system for micro and nano-satellites. Low cost mobile optical ground stations are now also being developed (Φ 200mm). Pointing error evaluation is planned using array of optical ground stations. 19

20 Thank you for your attention. 20