Hiroaki Shiraishi

Lunar Imaging Camera (LIC) is a small, compact and lightweight monochromatic imager designed and developed for LUNAR-A, Japanese lunar mission. The scientific objectives of the camera address impact cratering, tectonic processes, volcanic features, and optical properties of the regolith surface.The image sensor is a linear CCD and is aligned with the spin axis of the spacecraft, which orbits the Moon at altitudes of 200-300 km. The two-dimensional image is taken using the spin motion of the spacecraft. The total field of view (FOV) of the camera is 360°(around the spin axis)×14.6°(along the CCD-array). LIC obtains an image in one spin. The angular resolution of the camera is about 20 arcsec/pixel at a spin rate of 3 rpm. The spatial resolution is about 25 m/pixels at the surface when the altitude is 250 km. The spin axis of the LUNAR-A approximately points toward the Sun, therefore, LIC can take images of the lunar surface with highly oblique illumination conditions near the terminator. A series of pre-flight tests of LIC was performed. In those tests, the hardware performance and the functions of LIC were verified and the data for radiometric and geometric corrections were obtained. This paper outlines the scientific objective, characteristics of LIC, the procedure and the results of the pre-flight tests and the operation plan of LIC.

A hard landing probe "penetrator" has been thought to be a very useful tool for planetary exploration, because it provides cost-effective capability of deploying scientific instruments on planetary surface and subsurface. But development of the penetrator for planetary exploration requires better understanding penetration dynamics in geological materials. The present paper describes some experimental results on the penetrator dynamics obtained during the course of the development of the LUNAR-A penetrator. Special emphasis is placed on understanding the effect of the oblique incidence and the attack angle of the penetrator on penetration depth and a final attitude at the rest position. Many impact experiments into a simulated lunar surface material are made using penetrators 30 mm in diameter, and the penetration characteristics (penetration path length and inflection angle) are investigated as functions of impact velocity, penetrator shape, impact angle and attack angle. The results indicate that the torque applied to the penetrator in cases of the impact with a finite attack angle changes the penetration characteristics significantly. The experimental data also suggests that the impact angle does not have a substantial effect on penetration path length and that the truncation of the nose tip from a conical nose is efficient to stabilize the penetration orientation.

The accelerometer onboard LUNAR-A penetrator is developed to estimate the depth of emplacement and information on the physical properties of the lunar regolith. The decceleration record is also indispensable to design the structure of the outer case of lunar penetrator and to investigate quantitatively the shock-resistant capacity for the payload instruments. Investigation of several kinds of sensors' performance and improvement of the data acquisition system are made in order to design the most suitable accelerometer and its electronics for LUNAR-A penetrator. Using the piezoelectric type sensor with annular shear mode, the acceleration profiles with the sufficient accuracy are obtained under the actual flight conditions.