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Future China Geomagnetism
Satellite Mission (CGS)
Aimin Du
Institute of Geology and
Geophysics, CAS
2012/11/18 Taibei
OUTLINE
1- Promoting of the CGS mission
2- A brief introduction to the Constellation
3- Open discussion about the science
object of the CGS mission
Grenoble Workshop about CGS
On April 11, 2011
To Promoting the CGS Mission
In 2012, China Spacesat Co. Ltd. to design the CGS
It is confirmed that the Chinese companies have
ability to product the small satellites and suitable
rockets for the CGS mission.
Why are Chinese interested in
geomagnetic satellite missions?
It is related to Chinese history.
Magnetic Declination in China
Needham has shown that the credit for the discovery of
declination must go to the Chinese. Needham has tabulated
eighteen recorded Chinese compass observations of
declination covering the period about 720-1829. These are of
interest not only to historians but also to geophysicists, for
they represent the earliest recorded direct observations of the
Earth's magnetic field. The question of their validity is
therefore of great importance.
Petrus Peregrinus (1269)
Epistola de Magnete
Compass
CGS
MagNet
Swarm
CHAMP
Ørsted
Magsat
CONSTELLATION
• One satellite is in an orbit close to the equatorial plane
• Four satellites are in polar orbits separated by 45°
Mass:
115 kg
Inclination: 87.4°
Altitude:
Pre. rate:
450 km
-0.34 °/day
Spacecraft System Architecture
Fluxgate Magnetometers
Payload
Advanced Stellar Compass
Absolute Scalar Magnetometer
Spacecraft
Structure and Mechanism Subsystem
Attitude and Orbit Control Subsystem
Power Supply Subsystem
Platform
On-boardd Data Handing Subsystem
Thermal Control Subsystem
Communication Subsystem
Combined GPS, GLONASS,
Galileo and Beidou
Occultation technique
CGS Scientific Objectives
Component
Objectives
Contribute to the long phase of synoptic
Core
monitoring of the core field
Monitor flows in the core and their time
changes
Investigate the interplay between velocity and
magnetic fields
Mantle
Perform 3D tomography of mantle
Crust
 Construct the lithospheric magnetic map
conductivity
Environment Investigate
the time-space structure of the
magnetospheric and ionospheric sources on all
time scales
(Dominique and Jackson, 2010)
1. Core Field
Dynamics of the Earth’s core, as estimated from
the evolution of the magnetic field, evolves
on a variety of timescales.
外核
2. Monitor of MagnetosphereIonosphere Current System
3. Atmosphere and ionosphere
occultation technique
GPS
Atmosphere
CGS
Ionosphere
4. Crust Field
Deep Structure of the Earth and Concentration of
Metals in Lithosphere
Considerations of
the constellation
concept are for:
 Good coverage in spatial, local time and seasons.
 Separating of the core field, crust field, induced field.
 Equatorial satellite is for monitoring the daily
variations and equatorial current system.
80% data for single satellite
were lost
Kp < 2; LT ~ 21:00 - 03:00
Equatorial satellite monitoring
mid-low latitude currents by
the assimilation method
• Ring current: Storm-time geomagnetic disturbance
• Sq current: ionospheric dynamo
• Eqatorial ElectroJet (EEJ): cowling current
• Cross tail current: Substorm current
• Magnetopause current: Solar wind ram pressure
LONGITUDINAL PROFILE OF Bj FROM
MAGNETOSPHERIC CURRENTS
1
Dst 
N
H j
N
 cos
j 1
 B j
j
Local Time
18
00
06
12
B
o
o
12
o
o
Dst
(Le Guan et al., AG, 2004)
EQUATOR CURRENT SYSTEM
has a good longitudinal profile
Sq
C-F current
Cross Tail current
DEDUCE THE ELECTRIC POTENTIAL
IN POLAR REGION
THEN MAPPING TO THE MID-LOW LATITUDE MAGNETOSPHERE
FOR EXAMPLE
Geomagnetic Indices
Ring Current
Global profile in X component
on the ground
Magnetospheric
Current System
Auroral electrojet and Field-Aligned Current
SUMMARY
The constellation constellation with one nearequatorial orbit satellite and four polar orbit
satellites should contribute to:
 Separating of outer source field (noise) from the
satellite data.
 Modeling the magnetosphere-ionosphere current
system (signal).
 Discovering the small scale and short term variation of
core field.
 Constructing of mantle conductivity and lithosphere.
Thanks！