Tielong Zhang
On behalf of the CGS Team in the Institute of Geology and Geophysics, Chinese Academy of
Science
Spacecraft System and Payload
China Geomagnetism Satellite Mission
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
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
Ørsted
Vector magnetometerco-located withstar imager
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-C Launched on 21th November 2000700 km altitude, fixed local time 1030/2230
China Mission Baseline
5 satellites constellation
4 polar orbit + 1 equtorial orbit
Identical payload for all satellites
Spacecraft System Architecture
Spacecraft
Payload
Platform
Advanced Stellar Compass
Power Supply Subsystem
Attitude and Orbit Control Subsystem
Structure and Mechanism Subsystem
On-board Data Handing Subsystem
Thermal Control Subsystem
Communication Subsystem
d
Absolute Scalar Magnetometer
Fluxgate Magnetometers
Spacecraft Configuration
Main body plus tripod bracket
3 m deployable boom
Cross section ~0.4m2
S/C Configuration
Spacecraft Configuration
Octagon Prism
Φ0.8m×1.0m
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
Main Technical Performance Specification
Mass ( kg )Spacecraft 95
Bus 25
ACS 6
OBDH 8
TC/TM 10
Thermal 6
Power 25
Boom 15
Payload 10
System Contingency 10
Total 115
Spacecraft Mass Budget
Average ( W ) Maximum ( W )Spacecraft 40
AOCS 3
OBDH 15
TC/TM 10 30
Thermal 5
Power supply 7
Payload 20
Total 60 80
Spacecraft Power Budget
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
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
ASC
Magnetometer
GPS receiver
Attitude &Orbit determination
Sun sensor
Attitude control unit
Magnetorquers
On board CAN bus
OBDH System
AOC software
Attitude Control
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.
Thermal Control Subsystem (TCS)
Mode: passive means. Temperature range in cabin:-10°C - +35°C
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
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) 。
Orbital Parameter
。
Equatorial Polar
Altitude 550 km 550 km
Inclination 15 87.4 , 86.8
Orbit
RAAN variation
15°equatorial : period 49 day
87.4°polar : period 1060 day
86.8°polar : period 861day
15°equatorial
87.4°polar 86.8°polar
Orbit decay Equatorial Satellite
Orbit decay Polar Satellite 87.4
Orbit decay Polar Satellite 86.8
Orbit Decay
Equatorial Polar 87.4 Polar 86.8
Initial altitude km
550.0
Altitude after 5 year km
506.0 477.5 477.0
Time when altitude at 20
0km9 yr 8 mth 8 yr 4 mth 8 yr 4 mth
Eclipse
15°equatorial satellite , longest eclipse duration 35.8min
Durat i on(s)
1900
1930
1960
1990
2020
2050
2080
2110
2140
20150601 20160327 20170121 20171117 20180913 20190710 20200505
Date
Eclipse
87.4°polar satellite , longest eclipse duration 36min
Durat i on(s)
- 200
0
200400
600
800
1000
1200
1400
16001800
2000
2200
20150601 20160327 20170121 20171117 20180913 20190710 20200505
Date
Eclipse
86.8°polar satellite , longest eclipse duration 36min
Durat i on(s)
- 200
0
200400
600
800
1000
1200
1400
16001800
2000
2200
20150601 20160327 20170121 20171117 20180913 20190710 20200505
Date
Ground Stations for Data Receiving
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 downloadingGround
stationOrbits visible per day
Visible time per day (min)
Visible time per day (min)
Total visible time per day (min)
15° Sanya 7 5.689 10.234 61.444
87.4° Beijing 4 4.367 9.826 28.913
Kashi 4 6.119 9.651 31.817
Sanya 4 6.261 8.690 30.114
86.8° Beijing 4 2.783 9.874 25.670
Kashi 4 7.448 9.341 33.655
Sanya 4 3.843 9.294 26.583
Payload
Two fluxgate magnetometers
One scalar magnetometer
One star sensor