DEVELOPMENT OF SELENODETIC INSTRUMENTS FOR JAPANESE LUNAR EXPLORER SELENE-2

H. Hanada

1 ,

H. Noda

1 ,

F. Kikuchi

1 ,

S. Sasaki

1 ,

T. Iwata

2 ,

H. Kunimori

3 ,

K. Funazaki

4 ,

H. Araki

1 ,

K. Matsumoto

1 ,

S. Tazawa

1 ,

S. Tsuruta

1 1 National Astronomical Observatory 2 Japan Aerospace Exploration Agency 3 National Institute of Information and Communications Technology 4 Iwate University

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

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

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

Selenodetic Candidate instruments Observation method VLBI d-VLBI : Differential VLBI i-VLBI : Inverse VLBI SELENE-# 2 (Kikuchi) 2/3 (Kikuchi) Purpose Gravity Fields LLR Lunar Laser Ranging ILOM In situ Lunar Orientation Measurement 2 (Noda) 3 (Hanada) Librations Librations 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 ?

Molten core ? Solid inner core ??

MOON

Lunar Laser Ranging (LLR)

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.

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

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

Deployment

：

Where on the Moon ?

● Area : Data Contribution (~77%) 新規 ?

2,000km Schickard (44.3S, 55.3W) Tycho （ 43.4S,11.1W

） For Physical Librations: Southern Hemisphere far from A15 site about 2000km or more

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

Structure : Deformation by Earth’s Gravity

L D

D=20 cm (L = 14.14 cm), t = 1cm, “Cu” Deformation: less than 1 μm by Earth’s Gravity Field Taniguchi, 2010

Structure : Thermal Deformation of CCR

L D

(mm) 0,0000800 0,0000700 0,0000600 0,0000500 0,0000400 0,0000300 0,0000200 0,0000100 0,0000000 -0,0000100 Ряд21 Ряд16 Ряд11 Ряд6 Ряд1

L= 7.07 cm (D=10cm), < 3 nm

0,0000800 0,0000700 0,0000600 0,0000500 0,0000400 0,0000300 0,0000200 0,0000100 0,0000000 -0,0000100 (mm) Ряд21 Ряд16 Ряд11 Ряд6 Ряд1

L=14.14 cm (D=20cm), < 60 nm

NEC, 2010

Optical Performance (Ray Tracing Analysis) ccrtxm141_hex_1a 200mm ccr wit Beam Intensity at Image Surface 100.00

15:46:13 ccrtxm141_hex_1a 200 mm ccr with 1a defor 23-Jul-10 1.0

(0.000,0.000) DEGREES DEFOCUSING 0.00000

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

0.0E+00 6.9E-03 1.4E-02 2.1E-02 2.8E-02 3.4E-02 4.1E-02 4.8E-02 5.5E-02 6.2E-02 6.9E-02 DIAMETER OF CIRCLE (MM) 50.000

Efficiency (Streal Ratio) : 95.8 % .02888 mm Relative Field ( 0.000, 0.000 ) POSITION 1 Wavelength 532.00 nm.

Defocus: 0.000000 mm

L=14.14 cm (D=20cm), < 60nm

0.0000

Kashima, 2010

VLBI (Same-beam VLBI and Inverse VLBI)

VLBI (Very Long Baseline Interferometer) ？ Quasar Noise Noise

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 These new observations are expected to improve the lunar gravity field.

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.

Same-beam VLBI method : Improvement of lunar gravity model Simulation result

2 nd degree coefficients are improved by factor 3 or more.

 Moment of inertia Topography, Moho, GRAIL/LRO/Kaguya data  Constrain core density and radius

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

In-situ Lunar Orientation Measurement

（ＩＬＯＭ）

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

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

Development of BBM (Cooperation with Iwate univ.) 0.5m

0.1m

Objective Motor Frame Tube Mercury Pool Tiltmeter Tripod After Iwate Univ.

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

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 ?

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.

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

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