1. DEVELOPMENT OF SELENODETIC INSTRUMENTS FOR JAPANESE LUNAR EXPLORER SELENE-2
H. Hanada1, H. Noda1, F. Kikuchi1, S. Sasaki1, T. Iwata2, H. Kunimori3, K. Funazaki4, H. Araki1, K. Matsumoto1, S. Tazawa1, S. Tsuruta1
1 National Astronomical Observatory
2 Japan Aerospace Exploration Agency
3 National Institute of Information and 　　
　Communications Technology
4 Iwate University

2. KAGUYA (SELENE) → SELENE-2
Successful KAGUYA
Study of lunar landing mission(s) in JAPAN.
SELENE-2 lunar lander
SELENE Series 2, 3, …X
Launch by H-IIA in 2016 ?
Lander of 1000kg　including
scientific instruments of 300kg

3. Mission instruments for SELENE-2
Scientific instruments
Science of the moon
Geophysical/geodetic instruments
Geological instruments
Science from the moon
Astronomical instruments
Engineering instruments
Environmental instruments

4. Proposal for SELENE-2 SELENE-2 instruments for Lunar intererior study
◆Gravity observations by VLBI
　　 　　(Same-beam and Inverse VLBI)
◆Rotation observations by Lunar Laser Ranging
(new reflectors and a new ground network)
They are under review for onboard instruments
Another rotation observations by ILOM (In-situ Lunar Orientation Measurement) is proposed for SELENE-3

5. Selenodetic Candidate instruments
Observation method
SELENE-#
Purpose
VLBI
d-VLBI : Differential VLBI
2 (Kikuchi)
Gravity Fields
i-VLBI : Inverse VLBI
2/3 (Kikuchi)
LLR
Lunar Laser Ranging
2 (Noda)
Librations
ILOM
In situ Lunar Orientation Measurement
3 (Hanada)
Questions to be addressed:
Is there a core in the Moon ?
Is the core metallic ?
Is the metallic core liquid ?
Is there an inner core center of the liquid core ?

6. Molten core ? 　Solid inner core ??
MOON

7. Lunar Laser Ranging (LLR)

8. Lunar Laser Ranging
Laser Ranging from the Earth to the Moon started by Apollo in 1969 and continue to the present
4 reflectors are ranged:
Apollo 11, 14 & 15 sites Lunakhod 2 Rover
LLR attained the accuracy of less than 3cm with observations for longer than 25 years.

9. Objectives of future LLR
Ephemerides and/or Reference systems
Gravitational physics (General Relativity)
Geodynamics
Lunar science and Selenophysics

10. Issues on LLR Deployment：Where on the Moon ?
Type： “Array” or “Single”, “Prism or Hollow”
Size：Reflection Efficiency more than A11 or A15
Structure： Hard to be affected by gravitational and thermal effects
Optical Performance：Ray tracing simulation
Dihedral Angle Offset：What is the optimal value ?
Adaptive Optics：Option 10

11. Deployment ：Where on the Moon ?
● Area : Data Contribution (~77%)
新規?
2,000km
For Physical Librations:
　Southern Hemisphere far
from A15 site about 2000km
or more
Schickard
(44.3S, 55.3W)
Tycho（43.4S,11.1W） 11

12. Type : Array or Single, Prism or Hollow ?
Prism array of small aperture (Apollo, Luna)
Large range error due to optical libration
Single prism with large aperture
High accuracy of ranging
Extremely high quality prism is necessary :
⇒ less than 10cm size CCP
Single hollow with large aperture
Lighter weight
High accuracy
Change of dihedral angle due to
thermal distortion will be a problem 12

13. Structure : Deformation by Earth’s GravityL D
D=20 cm (L = cm),
t = 1cm, “Cu”
Deformation: less than 1 μm
by Earth’s Gravity Field
Taniguchi, 2010 13

14. Structure : Thermal Deformation of CCR
(mm)
(mm)
L= 7.07 cm (D=10cm), < 3 nm
L=14.14 cm (D=20cm), < 60 nm
NEC, 2010 14

15. Optical Performance (Ray Tracing Analysis)
Efficiency
(Streal Ratio)
: 95.8 %
L=14.14 cm (D=20cm), < 60nm
Kashima, 2010 15

16. VLBI (Same-beam VLBI and Inverse VLBI)

17. VLBI (Very Long Baseline Interferometer)？
Quasar
Noise
Noise

18. VLBI : Improvement of Lunar Gravity field
Orbiter
Same-beam (Differential) VLBI Method
◇Doubly Differenced One-way Range
Sensitivity : <20 cm
Survival module
Inverse VLBI Method
◇Differenced One-way Range
◇2-way range between orbiter and S-module
Sensitivity : <10-20 cm
In Japanese lunar landing mission SELENE-2, we proposed iVLBI mission for lunar gravimetry.
We will apply same-beam VLBI which is done for Kaguya and newly inverse VLBI method.
Measurement of same-beam VLBI is doubly differenced one-way range between these 4 paths.
Sensitivity of this measurement for orbit determination is about less than 20 cm.
Measurement of iVLBI is somewhat different from general VLBI.
First method is inverse VLBI.
These new observations are expected to improve the lunar gravity field. 18

19. Inverse VLBI
Radio signals transmitted from orbiter and lander are received at a ground antenna. These signals are synchronized via a reference signal from orbiter.
Received signals are cross correlated and a difference of the propagation time is measured.
Expected accuracy is several tens to several ps. These time difference corresponds to the distance of a few cm to a few mm.

20. Same-beam VLBI method : Improvement of lunar gravity model
Simulation result
2nd degree coefficients are improved by factor 3 or more.
Moment of inertia Topography, Moho, GRAIL/LRO/Kaguya data
 Constrain core density and radius

21. Conditions of the Simulations
Orbit parameters :
Perilune height = 100km,
Apolune height = 800km,
Orbit inclination = 70°
Landing position :
(0°、0°)
Tracking station :
Usuda(64m) and VERA(20m)
Data weight：
2-way Doppler = 1 mm/s, VLBI= 1 mm
Arc length of orbiter : 14 days.
Observation Period : 3 months

22. In-situ Lunar Orientation Measurement　　　　　　　　　　　　　　　　　　　　　（ＩＬＯＭ）

23. Principle of ILOM Observations
Telescope
Motion of a star in the view
Other objectives than lunar rotation
Pilot of lunar telescope （Engineering）　
Establishment of a lunar coordinate system

24. Star trajectory and Effects of Librations
After Heki
Trajectory of a star observed at the Lunar pole (June 2006– Sep.2007)
Decomposition of the trajectory
Polar motion and Librations extracted from the trajectory

25. Development of BBM (Cooperation with Iwate univ.) After Iwate Univ.
Objective
Motor
0.5m
Frame
Tube
Mercury Pool
Tiltmeter
Tripod
After Iwate Univ. 25 25

26. Specifications Aperture 0.1m Focal Length 1m Type PZT Detector CCD
Pixel Size
5μm×5μm (1″×1″)
Number of pixels
4,096×4,096
View
1°× 1°
Exposure Time
40s
Star Magnitude
M < 12
Wave length
550nm – 750 nm
Accuracy
1/1,000 of pixel size　(1mas)

27. Issues on ILOM: Technical issues
Improvement of the accuracy of centroid experiments
Correction of effects of temperature change upon star position
Keeping power during the night
Keeping warm during the night
Keeping inside thermally stable
Important condition of the lunar surface ?
How is the lunar dust ?
How dark is the lunar surface at night ?
How stable is the lunar surface ?
How quiet is the lunar surface ?

28. Summary
Technical developments and scientific evaluations for LLR, VLBI and ILOM are going on.
LLR and VLBI instruments are under review for SELENE-2 onboard instruments.
ILOM is prepared for SELENE-3.
We will investigate the lunar deep interior by further improving accuracy of observations of the lunar rotation and the gravity fields with new technologies.

29. Fabrication of CCR
ELID and Electroforming : with Omori Lab., RIKEN Inst.
ELID (Electrolytic Inprocess Dressing)
For making the “Master” of CCR
Surface Roughness: ±10 nm
Electroforming [Electrolysis]
Fabrication of One-unit CCR from “Cu”
Now trying to make a surface with Cu 29