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  • Small satellite conference 2007

    Tokyo Tech’s

    Technology Demonstration



    Junichi Nishida, Yoshihiro TsubukuJunichi Nishida, Yoshihiro Tsubuku

    LSS (Lab. for Space Systems) Tokyo Institute of Technology, Japan

  • Small satellite conference 2007

    IntroductionIntroduction CubeSat Project (10cm cubed picoCubeSat Project (10cm cubed pico--satellite)satellite)

    Tokyo Tech 2Tokyo Tech 2ndnd satellite projectsatellite project





    The 1st cubesat, CUTE-I launch



    Tokyo Tech 4th satellite projectTokyo Tech 4th satellite project

    TSUBAMETSUBAME has started !!has started !! Cute-1.7+APD II

    -Acquisition of satellite bus technologies

    -Has been operated more than 4 years !

    �Cute-1.7+APD Launched on February 2006

    �Had been operated for about a month

    �Cute-1.7+APD II will be launched in 2007

    �Applying some modifications to the 1st design

    -Trying new design methodology

  • Small satellite conference 2007


    �Satellite overview

    �Mission �Overview

    �Science mission

    �Engineering mission

    �General System overview �Specifications


    �Launch vehicle


  • Small satellite conference 2007

    ““TSUBAMETSUBAME”” overviewoverview

    • Polarized X-ray observation by using high-speed

    attitude maneuver with CMGs


    Development Guidelines

    • Student-leading system design

    • Promptly conduct high-technology

    demonstration on orbit

    Overview of TSUBAME

    TSUBAME means TSUBAME means ・・・・・・・・・・・・・・・・・・・・・・・・””SwallowSwallow”” in Japanesein Japanese

  • Small satellite conference 2007

    Mission overviewMission overview

    Polarized X-ray observation by using high-speed attitude maneuver with CMG

    2. Detection, Position determination

    3. High-speed attitude


    4. Start observation

    within 10 seconds

    1. Burst Occurrence

  • Small satellite conference 2007



    ~10 sec

    What are GRBs ?What are GRBs ? � Largest / brightest explosions at distant


    Where & When ?Where & When ? � Impossible to predict…

    � Prompt decay within ~ 1min !

    Mysteries ?Mysteries ? � Production mechanism and origin

    of GRBs yet to be understood…

    Science GoalScience Goal

    Astronomical observation of Polarized XAstronomical observation of Polarized X--rays and rays and γγ--rays rays

    from from GammaGamma--Ray Bursts (GRBs).Ray Bursts (GRBs).

  • Small satellite conference 2007

    Why XWhy X--ray Polarimetry Awaited ?ray Polarimetry Awaited ?

    But X-ray polarimetry is very difficult…

    � X-rays / γ-rays are detected as quantums, not as waves. � No sensitive X-ray polarimeter has been available.

    Crab pulsar


    Artist's impression of a GRB

    By past observation methods,

    we couldn’t solve the mysteries of GRBs.

    � Production mechanism and origin

    of relativistic jets from central engine. � Magnetic field geometry near the

    black hole.

    Focus on XFocus on X--ray / ray / γγγγγγγγ--ray polarimetry.ray polarimetry.

    X-ray polarimetry directly probes…

  • Small satellite conference 2007

    Mission InstrumentsMission Instruments

    (1) Wide-field Burst Monitor (WBM) � Detection of GRBs by monitoring a half of the sky.

    � Localization of GRBs with ∆θ ~10 deg accuracy. � Comparing counts in 5 “Scintillation” detectors.

    (2) Hard X-ray Compton Polarimeter (HXCP) � Use Compton-scat. Technique.

    � Energy range: 30-100 keV � FOV: ~ 100 deg2

    � Effective area: ~ 72 cm2



  • Small satellite conference 2007

    Design of Hard XDesign of Hard X--ray Polarimeterray Polarimeter

    � We have investigated an optimum design of HXCP with Monte Carlo Simulation.

    Multi-Anode Photo

    Multiplier Tube


    CsI Scintillator [Absorber]

    Plastic Scintillator [Scatterer]

    6 cm


    Photo Diode (APD)

    Horizontally polarized direction

    Photo-Absorption !

    Compton-Scattering !

    Photo-Absorption !

    Compton-Scattering !

    Passive Shield

    Vertically polarized direction

  • Small satellite conference 2007

    High Speed Attitude ManeuverHigh Speed Attitude Maneuver

    �Slewing 90°within 10s �Torque requirement :

    more than 60mNm �Lifetime : more than 1 year �As small and light as possible

    Basic of CMGs

    TSUBAME mounts four single gimbal CMGs



    CMG (Control Moment Gyro)CMG (Control Moment Gyro) is selected after careful investigation

  • Small satellite conference 2007

    CMG unit for space useCMG unit for space use

    �Developing a CMG unit which can be used in the orbit �Small size �Shield type �Low power consumption

    �Under development with Japanese company, Tamagawa Seiki

    Test model of CMG unit Planned CMG size and configuration

  • Small satellite conference 2007


    Attitude angular (quaternion)

    Angular velocity













    0 2 4 6 8 10 12 14

    Time [sec]

    A n g u le

    r V

    e lo

    c it y [ ra

    d /s

    ] .










    0 2 4 6 8 10 12 14 Time [sec]

    Q u at

    er n io


    Acceleration of wheels Burst occurrence

    Attitude maneuver Start observation

    10 seconds

    Reliable algorithm is required for prompt attitude maneuver with singular point avoidance

  • Small satellite conference 2007

    Engineering experimentEngineering experiment

    �A daughter satellite is released �Communications and measurement of tether formation flight dynamics �Recovering and docking the daughter satellite by controlling the tether

    Parent satellite Daughter satellite


    Tether deployment mission

    Ex. Tether Formation Flight

  • Small satellite conference 2007

    General System OverviewGeneral System Overview

    �Spec. of the satellite �Size : 50cm x 50cm x 40cm

    �Weight : 40kg

    �Designed lifetime : 1 year

    �Orbit : Sun-synchronous orbit

    �Altitude : 800km

    �Inclination : 98.6 deg.

    �Subsystems �Structure, Electrical Power

    �Command and Data Handling, Attitude Determination and Control

  • Small satellite conference 2007

    • Deploy two solar cell paddles

    • Three series and three parallel cells

    Electrical Power , StructureElectrical Power , Structure

    • Requirement from subsystem – Two solar cell paddles

    – CMG, Polarization detector

    subsystem Power(W)

    AD&C 27.27 C&DH 3 Comm 8.56

    Structure 8 Mission(GRB) 9.73

    Electrical Power Structure




    Eclipse Power(W) 14.67 21.67 31.53 30.53 39.56








    Occurrence of GRB

    Table. Power of subsystems

    Table. Power consumption of each mission sequence

    Paddle deployment

    Components allocation

  • Small satellite conference 2007


    Magnetic sensor HMR300

    Gyro sensor GYROCUBE 3A

    • Estimated data volume • Hardware

    - COTS based high performance MPU - SDRAM

    • Radiation tolerant design

    • Attitude sensors - Sun sensor : side planes - Gyro sensor : 3 axis - Magnetic sensor : 3 axis

    • Attitude determination algorithms - QUEST, REQUEST, Extended Kalman Filter

    • Actuator - Magnetic torquer : 3 axis - Control Moment Gyros

    •Orbit determination - GPS

    Medium sun sensor

    bit/sec Mbyte/day

    Mission data 200 2.09

    Attitude data 1065 10.6

    HK data 58 0.89

    Table. Handling Data (Observation)

  • Small satellite conference 2007

    Launch vehicleLaunch vehicle

    JAXA (Japan Aerospace

    Exploration Agency) provides piggyback launch opportunities

    using H-IIA rocket TSUBAME satellite is

    nominated (Priority A) for launch

    in 2009 (planned)

    H-IIA Rocket Launch

  • Small satellite conference 2007


    • Mission

    – X-ray polarimetry of Gamma-ray bursts

    – High speed attitude maneuver using CMGs

    • Conceptual design

    – Specifications

    – Subsystems

    We are now developing TSUBAME satellite by stude