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 Why are Chinese interested

inin

geomagnetic satellite geomagnetic satellite

missions?missions?

It is related to Chinese history.

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.

Magnetic Declination in China

CGS

Compass

MagNet

MagsatØrstedCHAMP

Swarm

Petrus Peregrinus (1269)Epistola de Magnete

CONSTELLATION• One satellite is in an orbit close to the equatorial plane One satellite is in an orbit close to the equatorial plane

• Four satellites are in polar orbits separated by 45° Four satellites are in polar orbits separated by 45°

Mass: 115 kg

Inclination: 87.4°

Altitude: 450 km

Pre. rate: -0.34 °/day

Spacecraft System Spacecraft System ArchitectureArchitecture

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

Combined GPS, GLONASS,Galileo and Beidou

Occultation technique

Component Objectives

Core

Contribute to the long phase of synoptic monitoring of the core fieldMonitor flows in the core and their time changesInvestigate the interplay between velocity and magnetic fields

Mantle Perform 3D tomography of mantle conductivity

Crust Construct the lithospheric magnetic Construct the lithospheric magnetic map map

Environment Investigate the time-space structure of the magnetospheric and ionospheric sources on all time scales

CGS Scientific Objectives

(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.

核幔界面外核

2. Monitor of Magnetosphere-Ionosphere Current System

AtmosphereIonosphere

GPSCGS

3. Atmosphere and ionosphere occultation technique

4. Crust Field Deep Structure of the Earth and Concentration of Metals in Lithosphere

古古亚洲成矿域亚洲成矿域

环太平洋成矿域

环太平洋成矿域

喜马拉雅喜马拉雅 -- 特提斯成矿域

特提斯成矿域

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

Local Time0012 18 06 12

Dst

B

oo

o

o

j

N

j j

jst B

H

ND

1 cos

1

(Le Guan et al., AG, 2004)

EQUATOR CURRENT SYSTEM has a good longitudinal profile

Sq

C-F current Cross Tail current

DEDUCE THE ELECTRIC POTENTIALIN POLAR REGION

THEN MAPPING TO THE MID-LOW LATITUDE MAGNETOSPHERE

Geomagnetic IndicesGlobal profile in X componenton the ground

Magnetospheric Current System

Ring Current Auroral electrojet and Field-Aligned Current

FOR EXAMPLE

SUMMARY

The constellation constellation with one The constellation constellation with one near-equatorial orbit satellite and four near-equatorial orbit satellite and four polar orbit satellites should contribute to: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！