Exploration of Planetary Interior

Development of Penetrator System★ Description of LUNAR-A Spacecraft・ Spin-Stabilized Cylindrical Shape・ 2.2 m max. in diameter × 1.7 m in height・ Weight : wet mass 540kg (Fuel 190 kg)
including two penetrator modules (45kg ×2)★ LUNAR-A Mission Objectives
・ Technological demonstration of penetrator system and Network Science in Planetary Exploration
・ Investigation of lunar internal structure by seismometry and heat-flow experiment on unmanned mission
・ Better understanding of bulk composition and early thermal state to clarify the origin and evolution of the Moon
Left figure show the deployment sequence of LUNAR-A penetrator module. Firstly, thepenetrator is released from the spinning spacecraft like a Frisbee style. Next, the orbital
velocity around the Moon is cancelled by a de-orbit motor ignition. Then, during the freefall, the attitude control system is used to reorient 90 degrees and to align the penetrator
module vertical to the lunar surface. Finally, the carrier system is separated and thepenetrator will hit on the lunar surface at the velocity of 300 meters per second. At thistime, LUNAR-A penetrator will encounter the large impact shock more than five
thousands G and penetrate to a depth of 2 or 3 meters.

Middle figure shows a diagonal view of LUNAR-A Penetrator Module. Total length is about one
point five meters, and total weight is about forty-five kilograms. Just half of the right in thisfigure is the penetrator itself, and on the left side, we call carrier system, which consists of deorbit motor and attitude control system. The right figure shows the inside of penetrator body, its
length is seventy-six centimeters, fourteen centimeters in diameter and its weight is about
fourteen kilograms. Accelerometer is used to know the impact velocity and penetration depth, byintegrating with time and tiltmeter is used to know the attitude of penetrator in the lunar regolith.

Two-component seismometer and tiltmeter are installed inside gimbals mechanism to adjust theirattitude and direction after penetration. Five thermal conductivity sensors and eleven thermocouples
are attached to the body surface. On the other hand, seven absolute thermometers are distributed
from the nose to the tail. Using these thermo-sensors, we can get the data necessary to estimate theheat-flow value in the lunar regolith. And other supporting instruments, sensor electronics, dataprocessing unit, communication system, 400MHz-UHF antenna, primary batteries are also equipped.
The penetrator body is designed to be a combination of a truncated ogive nose and a cylindrical partand it is made from CFRP (Carbon fiber reinforced plastic).

3-axis Acceleration Record

Numerical Simulation of Penetration

Depth (m)1 msec time step

1ｍX (m)Seismometry
・ Determine the meteoroid impact flux on the farside of the Moon･ Determine the seismic activity of the farside of the Moon･ Determine the seismic structure of the deep mantle
・ Determine the size and physical properties of the core

LUNAR-A Seismometer
Synthetic Response Curve
Diaphragm Spring

Cu-coil（Φ-20μm）

Relative output

Scientific Objectives

50 mm

Seismic Observation Test
★ Description of Seismic Observation• Setup on the tunnel of Inuyama Seismic Observatory in Central Japan• Simultaneous observation by several types of seismometers• Remote-operation of penetrator system by tele-communication onboard S/C• Observation Target : Micro-tremor with very small amplitude★ Key Items of Evaluation for Seismic System
Inuyama Seismic Observatory
・ Sensor performance before and after impact test
・ Noise level of sensor, preamplifier and analog filter system
・ Long-term stability of sensor－gimbals system for natural ground motion

Magnetic Circuits

Heat-Flow Experiment
・ Determine the heat flow values at two different sites on the Moon･ Determine the average heat flow values of whole Moon･ Determine the bulk abundance of the refractory elements

Frequency(Hz)25cm

Description of L-A Seismometer・ Short-period electromagnetic type sensor with velocity sensitive・ A moving coil suspended by a pair of three spiral-beam spring・ Natural frequency : 1.0～1.2 Hz・ Generator constant : 10.8 Volt / kine
・ Dimensions：Φ50mm×50mm in height・ Weight：680 g （1 horizontal and 1 vertical components)

Broadband SeismometerMark ProductL-4 geophone

LUNAR-A

Short-period Seismometer

Heat-Flow Probes

Recent ProgressCu-plate

After Impact Test

Surface Heat Flow ValueHeater
20 mm

Q = K × dT/dzlead wire

Thermocouple

High rigid epoxy resin+ glass micro-balloon

Electronics

Gimbals
BatteryU-HybridAntenna

Battery

Configuration of Thermal Conductivity Sensor
Measurement Principle of Thermal Conductivity⇒Point-heat source method
Dimensions：Φ-12mm×5mm in height
0.025kelvin resolution, 0.01kelvin accuracy

Seismometer

Relative Temperature Sensor (Pt-thermometer)
Absolute Temperature Sensor (K-type thermocouple)
Thermal Conductivity Probe (heater+thermocouples)Hea
Te tin g
mp up
era anture d
R ise

Temperature Base Point

Temp. Rise (μV)

DPU√time(sec)★Description of Last QT Level Impact Test
・ Almost fully integrated hardware components and FM software are installed.
・ Two types of reset sensors and a coupling electronic circuit are equipped for backup system.
・ Noise reduction of electronics and partially improvement on the link margin for communication system.
・ Careful arrangements for experimental procedure and workmanship in test field to avoid ESD input.

Checkout of Gimbals
Davis GunandSeismometer(2) LUNAR-A project had been reviewed by both the internal and external
review boards from the viewpoint of technology and management in2004.
Spacecraft and Carrier System :Suspension of development and safekeeping under purged N2 gas
condition
Penetrator System :Further improvement and some modifications are required

Impact conditions : 330 m/sec, 8.7 deg attack angle
Successfully communicated with the penetrator just after impact
All the functions of instruments work well after impact
Detailed examination of instruments and evaluation of sensor
performance were made after return to Japan.

★A new 3-year program to solve the penetrator technology issues
was initiated in 2005, and now half-way complete.
(1) Improvement of electronics design for robustness against ESD, and addition of back up
system for possible malfunction which occurred in the QT level experiment in 2003.
(2) Assurance of robustness on communication system and of a sufficient margin on link
between the penetrator and the spacecraft.

Outline of Mission Schedule
4★New Electric Parts★Sensor and Circuitfor Backup System(1) Component Modelfor Backup System

Design Analysis

Evaluation Test
Impact Test

Manufacturing

FY. 2005

FY. 2006

5 6 7 8 9 10 11 12 1 2 34 5 6 7 8 9 10 11 12 1 2 3FY. 200745 6 78 9 10

Verification of Shock durability
for the newly designed components
Verification of recovery
for malfunction of ’03 QT test(2) Integrated Modelwith Back up System

Improvement and Completion ofData Processing and Comm. Unit

★Re-Designed Components(DPU and Com. System)(3) Fully Integrated Model

We have put on a three-year program into effort
to solve the penetrator technology issues

Calibration Profiles before and after Impact
Test

Result of Last Impact Test

Impact Test Facility(1) LUNAR-A mission has been suspended and the launch date is notdetermined since 2004, because of the following two reasons.
Mother Spacecraft : Recall and replacement of some thruster bulbs usedfor Reaction Control System.
Penetrator : A malfunction observed in the qualification level test (QT)
performed in November, 2003

Technical Issues

Future Prospect★ LUNAR-A project was cancelled in Feb. 2007.
(1) There is no redundancy for mission success because of only twopenetrators, higher reliability and robustness are required for JAXA
confidence level.
(2) More than ten years have passed since the mother S/C was manufactured,
the deterioration in the quality of the instruments onboard the mother S/Cbecause of the long-term storage.

★Final QT level impact test will be fired in FY2007
and we aim for completion of penetrator technology

Luna-Glob Mission★ Description of Luna-Glob Satellite
・ 3-axis stabilized satellite, 2.3 ton in total weight・ Single launch by Soyuz-Fregat2 rocket in 2012 (TBD)
・ 1 Main S/C, 1 Lander, and 4 LUNAR-A penetrators
・ Geophysical Network Observation by 5 points(possibly, including seismometer onboard Lander)★ Utilization of Penetrator System on Follow-on missions⇒ Luna-Glob mission in collaboration with Russia★ Application and Modification of Payload Instruments⇒ Post-SELENE mission in JAXA and other lander missions

Simulated Soil

Penetrator Module
Checkout of Communication System and Seismometer-Gimbals Mechanism

Luna-Glob

Post-SELENE