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A BRIEF INTRODUCTION TO GEOSPACE DOUBLE STAR PROGRAM

 

LIU Zhengxing

 

Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100080, China

 

ABSTRACT

The Geospace Double Star Project (DSP) contains two small satellites operating in the near-earth equatorial and polar regions respectively. The tasks of DSP are: (i) to provide high-resolution field, particle and wave measurements in several important near-earth active regions which have not been covered by existing ISTP missions, such as the near-earth plasma sheet and its boundary layer, the ring current, the radiation belts, the dayside magnetopause boundary layer, and the polar region; (ii) to investigate the trigger mechanisms of magnetic storms, magnetospheric substorms, and magnetospheric particle storms, as well as the responses of geospace storms to solar activities and interplanetary disturbances; (iii) to set up the models describing the spatial and temporal variations of the near-earth space environment. To complete the mission, there are eight in struments on board the equatorial satellite and the polar satellite, respectively. The orbit of the equatorial satellite is proposed with a perigee at 550 km and an apogee at 60000 km, and the inclination is about 28.5º; while the orbit of the polar satellite with a perigee at 700 km and an apogee at 40000 km, as well as an inclination about 90º. The equatorial and polar satellites will be launched in December 2003 and June 2004 respectively to take coordinating measurements with Cluster II and other missions.

Key words:  Solar-terrestrial space physics, double star exploration program, International cooperation

I. SCIENTIFIC OBJECTIVES OF GEOSPACE DOUBLE STAR PROGRAM

Geospace Double Star Program (DSP) contains two small satellites operating in the near-earth equatorial and polar regions not covered by the exiting ISTP missions.

1. Exploration Tasks

(1) To detect the temporal-spatial variations of fields and particles in the near earth equatorial regions those are the near earth plasma sheet and its boundary layer, the substorm injection region, the radiation belt ring current and the plasmasphere, and the dayside magnetopause boundary layer region.

(2) To detect the temporal-spatial variations of fields and particles in the near earth polar active regions those are the auroral acceleration region and the near earth cusp region and the polar cap region connected with the high latitude boundary layer.

(3) To coordinate with Cluster II mission to detect: (a) 3-D small-scale structures and variations of fields and particles in the solar wind, bow shock, and magnetosheath; (b) 3-D small scale structures and temporal-spatial variations of fields and particles in the magnetopause boundary layer including the low latitude boundary layer (LCBL), cusp region, and high latitude boundary layer (HLBL).

 

2. Main Research Objectives

    The main objectives are to investigate the trigger mechanism and physical models of geospace storms.

(1) To understand the trigger mechanism of substorms and magnetic storms, their global response to the interplanetary condition, and the processes of magnetotail and ionospheric disturbances.

(2) To study the temporal-spatial variations of near earth magnetospheric particles, to understand the physical processes of particle acceleration, diffusion, injection, precipitation, and up-flowing during the magnetospheric particle storms.

(3) To coordinate with Cluster II, to investigate the 3-D small-middle scale structures and magnetic reconnection in the magnetopause boundary layer for different interplanetary conditions, as well as the disturbance processes transferring to the ionosphere.

 

II.  THE PAYLOAD OF DSP

16 instruments are mounted on DSP satellites to achieve the scientific objectives. Among these instruments, FGM, PEACE, HIA, ASPOC, EPS-E, and STAFF are provided by Cluster PI groups. EPS-P and NAI are developed with joint efforts from CSSAR of CAS, Germany, National University of Ireland and Swedish Institute of Space Science.

The rest of instruments are fabricated by CSSAR, Chinese Academy of Sciences. Nine instruments are mounted on the equatorial satellite, other ten are on the polar satellite.

1. There are four Types of Instruments Onboard in the DSP Mission

(1) For magnetic field measurements

It is the flux gate magnetometer. The main scientific objectives are to make an accurate measurement of the magnetic field vector, and determine the temporal and spatial variations of magnetic fields. The data of the magnetic field measurement are also used in the analysis of the particle distribution data.

(2) For partic1e measurements

There are 8 instruments designed to measure the velocity distribution and/or energy spectrum of particles with different energy ranges, including the low energy range (leV-40 keV), intermediate energy range (40 eV-1.5MeV), and high energy range (1 MeV-1000 MeV). The main scientific objective is to obtain temporal and spatial variation of particles during quiet times and active times.

(3) For active spacecraft potential control

Its main scientific objective is to control the satellite potential and ensure the measurement accuracy of low energy plasmas.

(4) For low frequency wave measurements

 

The major scientific objective is to measure the low frequency electromagnetic waves driven by plasma instabilities, and study the heating, acceleration, diffusion and precipitation processes of particles.

 

2. Mass, Power and Data Rate of Payload on the Near Equatorial Satellite

 

No

Instrument

Mass (kg)

Power (W)

Data rate (Kbps)

1

FGM

3.0

2.5

0.80

2

HIA

3.0

3.0

3.12

3

HEED

2.2

2.0

0.19

4

HEPD

2.2

2.0

0.19

5

HID

2.2

2.0

0.64

6

ASPOC

2.5

3.0

0.13

7

PEACE

6.5

5.0

3.54

8

STAFF

3.6

5.0

3.00

Total

25.2

24.5

11.61

 

3. Mass, Power and Data Rate of Payload on the Polar Satellite

 

No

Instrument

Mass (kg)

Power (W)

Data rate

1

FGM

3.0

2.5

0.80

2

LEID

4.5

4.0

3.00

3

NIA

4.5

4.0

4.90

4

HEED

2.2

2.0

0.19

5

HEPD

2.2

2.0

0.19

6

HID

2.2

2.0

0.13

7

PEACE

6.5

5.0

3.00

8

LFEW

4.0

5.0

3.00

Total

29.1

26.5

15.21

 


III. ORBITS OF TWO SATELLITES

To realize the scientific objectives, the orbits of two satellites are proposed as the following:

The near equatorial satellite is with perigee: about 550 km, apogee: about 60000 km (about 10RE), inclination: about 28.5o and Kepler period: 20.91h.

The polar region satellite is with perigee: about 700 km, apogee: about 40000 km, inclination: about 90o and Kepler period: 7.27h.

 

IV. THE SPACECRAFT

 

(1) The configuration of DSP spacecrafts: Each DSP spacecraft is cylindrical, a size of l230 mm high and 2100 mm in diameter, with two 2.5 m experimental rigid booms and two axial telecommunication antenna booms.

 

(2) The spacecrafts of DSP are spin-stabilized with a spin rate of 15±10% rpm. The spin axis is perpendicular to the ecliptic plane.

 

The mass, power, and data rate of the two satellites:

 

Satellite
Total mass(kg)
Total power(W)
Date rate (kbits/s)
DSP-E
270
207
11.3
DSP-P
270
207
14.2

 

V. THE LAUNCH VEHICLE AND THE LAUNCHING SITE

 

1. The Launch Vehicle

The Long March (L-M)-2C is used to launch the satellites.

2. The Launching Site

The near earth equatorial satellite and the polar satellite will be launched respectively from Xichang Satellite Launch Center (XSLC) and Taiyuan Satellite Launch Center (TSLC) in China.

3. Ground Receiving Stations

Beijing Ground Receiving Station: In Miyun County, Beijing, 70 km northeast of the city, its antenna diameter: 11 m.

Shanghai Ground Receiving Station: In Sheshan County, Shanghai, 100 km southwest of the city, its antenna diameter: 25 m.

The Villafranca (Spain) Ground Receiving Station of ESA may be used to receive partial data of the two satellites.

4. The Launch Date

The DSP-E satellite will be launched in Dec. 2003. The DSP-P satellite will be launched in June 2004.

 

5. The Life Span of the Spacecraft

The DSP-E satellite is designed to operate for 18 months. The DSP-P satellite is designed to operate for 12 months.

VI. INTERNATIONAL COOPERATION

Double Star Program will cooperate with ESA Cluster II mission and other ISTP missions for maximizing the scientific achievements.

The Agreement between ESA and CASA on the DSP cooperation between the two sides has been signed in July, 2001.

(1)  Cooperation on instruments

Some instruments for DSP have been in cooperation with several Cluster PI groups and other research groups in Europe.

FGM/CLUSTER groups will provide two flux gate magnetometers for both satellites.

ASPOC/CLOSTER group will provide two instruments of active spacecraft potential control to both satellites.

PEACE/CLUSTER group will provide two instruments of plasma electron and current detectors for both satellites.

HIA/CLUSTER group will provide a hot ion detector for DSP-E satellite.

The EPS-P group of Germany and NAI group of National University of Ireland and Swedish Institute of Space Science will cooperate with CSSAR to develop the neutral atom imager for DSP-P satellite.

The STAFF group will provide a wave detector for DSP-E satellite.

(2) European Space Agency will provide Villafranca Satellite Ground Station to receive a part of the DSP data.

(3) Two agencies will share the data and collaborate on the scientific investigation.

(4) ESA will provide technique support for the integration of the European-furnished payload elements, and some other technologies.

    (5) Any further international cooperation, such as the cooperation between DSP and missions of IACG, is welcome.


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