Japan Aerospace Exploration Agency

About: Japan Aerospace Exploration Agency is a facility organization based out in Tokyo, Japan. It is known for research contribution in the topics: Galaxy & Telescope. The organization has 4327 authors who have published 12054 publications receiving 208330 citations.

Lunar global shape and polar topography derived from Kaguya-LALT laser altimetry.

Abstract: A global lunar topographic map with a spatial resolution of finer than 0.5 degree has been derived using data from the laser altimeter (LALT) on board the Japanese lunar explorer Selenological and Engineering Explorer (SELENE or Kaguya). In comparison with the previous Unified Lunar Control Network (ULCN 2005) model, the new map reveals unbiased lunar topography for scales finer than a few hundred kilometers. Spherical harmonic analysis of global topographic data for the Moon, Earth, Mars, and Venus suggests that isostatic compensation is the prevailing lithospheric support mechanism at large scales. However, simple rigid support is suggested to dominate for the Moon, Venus, and Mars for smaller scales, which may indicate a drier lithosphere than on Earth, especially for the Moon and Venus.

The global distribution of pure anorthosite on the Moon

Abstract: It has been thought that the lunar highland crust was formed by the crystallization and floatation of plagioclase from a global magma ocean, although the actual generation mechanisms are still debated. The composition of the lunar highland crust is therefore important for understanding the formation of such a magma ocean and the subsequent evolution of the Moon. The Multiband Imager on the Selenological and Engineering Explorer (SELENE) has a high spatial resolution of optimized spectral coverage, which should allow a clear view of the composition of the lunar crust. Here we report the global distribution of rocks of high plagioclase abundance (approaching 100 vol.%), using an unambiguous plagioclase absorption band recorded by the SELENE Multiband Imager. If the upper crust indeed consists of nearly 100 vol.% plagioclase, this is significantly higher than previous estimates of 82-92 vol.% (refs 2, 6, 7), providing a valuable constraint on models of lunar magma ocean evolution.

Mechanical properties of corrugated composites for candidate materials of flexible wing structures

Abstract: Corrugated-form composites are expected to be very flexible in the corrugation direction and stiff in the direction perpendicular to the corrugation. In this study, the corrugated composites manufactured from carbon fiber plain woven fabrics draw attention as a candidate material for flexible structural components, e.g. morphing wings. In-plane stiffness and strength of the original corrugated composites are evaluated through the tensile and bending tests in both in-plane longitudinal and transverse directions. A simple analytical model for the initial stiffness of the corrugated composites is developed, and the predictions are compared with the experimental results. Moreover, some improvements, installing of stiff rod and flexible rubber, are attempted for the creation of smooth aerodynamic surface and the improvement of stiffness. Mechanical properties of the modified corrugated composites are also evaluated and compared with those of the original corrugated composites. The applicability of the corrugated composites to the flexible wing structures are discussed based on the specific stiffness, longitudinal-to-transverse stiffness ratio, etc.

Three-Dimensional Structure of Hayabusa Samples: Origin and Evolution of Itokawa Regolith

Abstract: Regolith particles on the asteroid Itokawa were recovered by the Hayabusa mission. Their three-dimensional (3D) structure and other properties, revealed by x-ray microtomography, provide information on regolith formation. Modal abundances of minerals, bulk density (3.4 grams per cubic centimeter), and the 3D textures indicate that the particles represent a mixture of equilibrated and less-equilibrated LL chondrite materials. Evidence for melting was not seen on any of the particles. Some particles have rounded edges. Overall, the particles’ size and shape are different from those seen in particles from the lunar regolith. These features suggest that meteoroid impacts on the asteroid surface primarily form much of the regolith particle, and that seismic-induced grain motion in the smooth terrain abrades them over time.

Electron acceleration by multi-island coalescence

Abstract: Energetic electrons of up to tens of MeV are created during explosive phenomena in the solar corona. While many theoretical models consider magnetic reconnection as a possible way of generating energetic electrons, the precise roles of magnetic reconnection during acceleration and heating of electrons still remain unclear. Here, we show from two-dimensional particle-in-cell simulations that coalescence of magnetic islands that naturally form as a consequence of tearing mode instability and associated magnetic reconnection leads to efficient energization of electrons. The key process is the secondary magnetic reconnection at the merging points, or the "anti-reconnection," which is, in a sense, driven by the converging outflows from the initial magnetic reconnection regions. By following the trajectories of the most energetic electrons, we found a variety of different acceleration mechanisms but the energization at the anti-reconnection is found to be the most important process. We discuss possible applications to the energetic electrons observed in the solar flares. We anticipate our results to be a starting point for more sophisticated models of particle acceleration during the explosive energy release phenomena.