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Spacecraft System and Payload

China Geomagnetism Satellite Mission. Spacecraft System and Payload. Tielong Zhang On behalf of the CGS Team in the Institute of Geology and Geophysics, Chinese Academy of Science. Magsat. First high resolution vector field measurement Nov 1979 – May 1980 – 7 month data.

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Spacecraft System and Payload

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  1. China Geomagnetism Satellite Mission Spacecraft Systemand Payload Tielong Zhang On behalf of the CGS Team in the Institute of Geology and Geophysics, Chinese Academy of Science

  2. Magsat • First high resolution vector field measurement • Nov 1979 – May 1980 – 7 month data Vector magnetometer and star tracker are not collocated Degraded vector data accuracy

  3. Ørsted • 1991: Selection of idea to fly a magnetometer on a Danish satellite • 1991-1992: Feasibility study • International Review, March 1992 • 1993: Funding for the total project decided • Work package contracts • Research Announcement • 1995: First Ørsted International Science Team (ØIST) meeting • 100 participants, 60 foreign • 1997: Ready for launch! • 1999: Launch on February 23 Vector magnetometer co-located with star imager

  4. Heritage • ØrstedLaunched on 23th February 1999 Polar orbit, 650-850 km altitudeall local times within 790 days (2.2 years) • CHAMPLaunched on 15th July 2000low altitude (<300 - 450 km)all local times within 130 days • SAC-CLaunched on 21th November 2000700 km altitude, fixed local time 1030/2230

  5. China Mission Baseline • 5 satellites constellation • 4 polar orbit + 1 equtorial orbit • Identical payload for all satellites

  6. Spacecraft System Architecture

  7. Spacecraft Configuration • Main body plus tripod bracket • 3 m deployable boom • Cross section ~0.4m2

  8. S/C Configuration

  9. Spacecraft Configuration • Octagon Prism • Φ0.8m×1.0m

  10. S/C Configuration • Main body Shape: • Octagon prism with a tripod bracket • On orbit status: • 5m boom attaches to the bracket • Size: • Φ0.8m×3.5m (in Launch Status ); • Φ0.8m×8.5m (in Flight Status) boom folded boom deployed

  11. Main Technical Performance Specification

  12. Spacecraft Mass Budget

  13. Spacecraft Power Budget

  14. Structure and Mechanism Subsystem (SMS) • Structure: • The structure consists of several aluminum-honeycomb panels. • Mechanism: • Mainly mechanism:2 deployable Boom (for each is 2.5m long) • Function: • ensure a magnetic clean environment • stable accommodation for the sensors. Boom folded Boom deployed

  15. Attitude and Orbit Control Subsystem (AOCS) • Attitude & Orbit Determination • ASC (star imager with 3 camera head)×1 • Magnetometer×1 • Sun Sensor×1 • GPS Receiver×1 • Attitude Control • Gravity gradient stabilization • 3 Magnetorquers for active control OBDH System AOC software On board CAN bus ASC Attitude control unit Magnetometer Magnetorquers GPS receiver Sun sensor Attitude Control Attitude &Orbit determination

  16. RF Communication Subsystem (RFCS) • The RFCS is responsible for • Telemetry, Tracking and Command (TT&C), • Payload data transmission. • The RFCS consists of communication receive & transmit device and two antennas. • Uplink and downlink in S-band • Downlink data rate is 2 Mbit/s; • Uplink date rate is 2 kbit/s.

  17. Thermal Control Subsystem (TCS) • Mode: passive means. • Temperature range in cabin:-10°C － +35°C

  18. On-board Data Handling Subsystem (OBDH) • The OBDH is responsible to: • data and task management; • onboard timing; • onboard command • The OBDH consists of : • on board computer, • tele-command unit, • payload data storage and control unit, • thermal control unit, • On board net: CAN bus. • On board computer: • 20 MHz CPU • 2 MByte SRAM

  19. Power Supply Subsystem (PSS) • The PSS is responsible to: • Power generation, • Power distribution • Power storage. • Operation mode： • the solar-panel generates electrical power in sunlight • Li-ion batteries supply power in eclipse. • PSS consists of solar panels, batteries and Power Control Unit • Solar panels： • GaAs triple-junction • body-mounted solar panels • Area: ~3m2 • Output power: 150w in average; • Batteries：7-cell Li-ion battery packs, 10Ah; • Single-primary-bus mode distributes power to equipments (28.5±1V)。

  20. Orbital Parameter 。

  21. RAAN variation 15°equatorial：period 49day 87.4°polar：period 1060day 86.8°polar：period 861day Orbit 15°equatorial 87.4°polar 86.8°polar

  22. Orbit decay Equatorial Satellite

  23. Orbit decay Polar Satellite 87.4

  24. Orbit decay Polar Satellite 86.8

  25. Orbit Decay

  26. Eclipse • 15°equatorial satellite，longest eclipse duration 35.8min

  27. Eclipse • 87.4°polar satellite，longest eclipse duration 36min

  28. Eclipse • 86.8°polar satellite，longest eclipse duration 36min

  29. Ground Stations for Data Receiving

  30. Ground Stations for Data Receiving • Equatorial satellite: Sanya station, 60 min visible time per day • Polar satellite, 3 stations, 80 min visible time per day for data downloading

  31. Payload • Two fluxgate magnetometers • One scalar magnetometer • One star sensor

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