1. Space environmental study for ASTROD I
Zhang Qingxiang Wangli Shi Wanglin Hou Xinbin Song Zhenji
Deep Space Exploration & Space Science Technology Division
Research & Development Center，CAST

2. Outline
Introduction
Space environment for ASTROD1
Preliminary space environment effect analysis
Suggestion for space environment monitor onboard ASTROD1
Conclusion

3. 1. Introduction
CAST setup Deep Space Exploration & Space Science Technology Division at R&D center to promote space science missions.
DESSTD began to work together with ASTROD team
DESSTD took parting in a ASTROD workshop at Purple Mountain Observatory
...

4. ASTROD 1(Mini -ASTROD)
Two-Way Interferometric and Pulse Laser Ranging between Spacecraft and Ground Laser Station
Testing relativistic gravity 3-order-of-magnitude improvment in sensitivity;
Astrodynamics & solar-system parameter determination improved by 1-3 orders of magnitude;
Improving gravitational-wave detection compared to radio Doppler tracking (Auxiliary goal).
Wei-Tou Ni(1,2) and Diana N A Shaul(3) Solar, COsmic Ray and Environmental physics for/with ASTROD and ASTROD I

5. ASTROD 1 Orbit
For ASTROD I the distance from the Sun is 0.5 AU to 1.04 AU;
The orbit of ASTROD I is out of magnetosphere of Earth
ASTROD and ASTROD I: Progress Report

6. Key technology for ASTROD 1
Tree dimensions sensing capacitive
proof masses
μN proportional thrusters （Electric Propulsion thrusters ）
lasers and optics （5 lasers onboard ASTROD 1 ） ……
longevity and reliability of these technologies in the space environment is vital to success for ASTROD I.

7. 2. Space environments for ASTROD1
Galaxy Cosmic Ray
Solar event particles
Solar wind
Solar electromagnetic radiation

8. Galaxy Cosmic Ray All Elements in Periodic Table Energies in GeV
Found Everywhere in Interplanetary Space
Omnidirectional
Mostly Fully Ionized
Cyclic Variation in Fluence Levels
Lowest Levels = Solar Maximum Peak
Highest Levels = Lowest Point in Solar Minimum
Single Event Effects Hazard
Model: CREME96
Janet Barth: Radiation Environments

9. GCR energy and LET spectrum at 1AU calculated with CREAM96

10. GCR Gradients in the Heliosphere
Basd on data from IMP, Voyage and Pioneer, GCR flux increased with distance form Sun.
The gradient magnitude is 10% per AU at 1AU
4%per AU at 5AU
Difference between GCR flux at 0.5AU and 1AU will be less 10%, Using external radiation fluence at 1AU for ASTROD1 is conservative.

11. Solar event particles CME Solar Flares
Increased Levels of Protons & Heavier Ions
Energies
Protons - 100s of MeV
Heavier Ions - 100s of GeV
Abundances Dependent on Radial Distance from Sun
Partially Ionized - Greater Ability to Penetrate Magnetosphere
Number & Intensity of Events Increases Dramatically During Solar Maximum
Models
Dose - SOLPRO, JPL, Xapsos/NRL
Single Event Effects - CREME96 (Protons & Heavier Ions)
CME
Solar Flares
Janet Barth: Radiation Environments

12. Proton Event Spectra - Cycle 22
time φ0 k α r
2.45×1010
0.0236
1.108
0.996
1.622×1011
1.166
0.4015
0.994
3.631×1010
0.877
0.3841
0.998
1.230×1012
2.115
0.2815
1.660×1011
0.972
0.4410
0.993
Total Integral Proton Fluence
Janet Barth: Radiation Environments

13. SEP energy and LET spectrum at 1AU calculated with CREAM96

14. SEP Gradients in the Heliosphere
The gradient in peak intensity was found to be about R-3, and the total fluence gradient as R-2(NASA)
a 1/r+ heliocentric scaling is used for SPE, whilst no scaling is used for heliocentric distances greater than 1AU.(ESA)
Recommendations of NASA Sun-Solar System Connections(2005)
Radiation Exposure and Mission Strategies for Interplanetary Manned Mission – REMSIM(2004)
The SEP peak intensity at 0.5AU is 8 times of that at 1AU, total fluence at 0.5AU is 4 times of that at 1AU.

15. Solar wind
Stream of Charged Particles from Sun’s Corona electrons, protons, heavy Ions
Magnetized Plasma
Detected Out to 10 billion km from Earth by Pioneer 10
Velocity ~ km/s
Energy ~ keV/nuc

16. Solar wind plasma parameter
Electron
Density e
temperatureTe
Ion
Velocity vi
Ei/Ti
density i
Debye
Lengh
0.5AU(A)
4.27cm-3
10.6eV
702km/s
2573 eV 6m
0.5AU(B）
13.1 cm-3
68.2 eV
863 km/s
3888 eV
17m
A:come from Feldman, high speed solar wind environment scaled to 0.5AU
B: data from the SWOOPS(Solar Wind Observations Over the Poles of the Sun) instrument onboard Ulysses

17. Solar electromagnetic radiation
Solar electromagnetic radiation diffuses with distance from the sun at a rate of 1/R2.

18. 3 Preliminary space environment effect analysis
Total dose effect
Displacement damage
Single Event Effect
Optical darkening and thermal property changes
Optical contamination

19. Total dose effect

20. The Solar Orbiter will go into the inner heliosphere to 0.21 AU,
For a nominally shielded (4mm Al) silicon component is epected to receive a dose of 48 krad over the entire mission(5 years)
The effect of Total dose to microelectronic is not very serious for ASTROD1.

21. Displacement damage
CCD and laser LED may be degraded at very low proton fluence by displacement damage.
Allan H. JohnstonDisplacement Damage and SpecialIssues for Optoelectronics

22. Single Event Effect
Microelectronics are likely to occur different SEE.

23. Detectors will be flooded with “noise”.
Single event effect will be a major concerns for ASROD1 , especially during large SEP.
SOHO/LASCO Images

24. Effect to exposed material
optical darkening and surface thermal property changes due to synergistic effects between radiation, UV, thermal cycling, vacuum and contamination.

25. 4 Suggestion for space environment monitor onboard ASTROD1*/
The space environment definition is not very certain because we don’t have enough data.
It’s proposed that space radiation instrument onboard ASTROD1 satellite:
To space environment safety management of satellite and charge management of test materials.
Collect environment data in inner heliosphere It’s proposed to add space environment measurement as one of the scientific objects of ASTROD1

26. 5.conclusion
Studying the space environment and it’s effect as early as possible are very important for space mission success.
It’s proposed to add space environment measurement as one of the scientific aims of ASTROD1.

27. Thanks