[show abstract][hide abstract] ABSTRACT: After successful rendezvous observation and landing for surface sampling
from the near Earth asteroid 25148 Itokawa by the Hayabusa MUSES-C
mission Japan is preparing for follow-up minor body missions in the
post-Hayabusa era According to Japan s minor body exploration roadmap as
well as on-going discussion within the JAXA ISAS Minor Body Exploration
Working Group which is consisted of planetary scientists and
astronautical engineers from all over Japan the most recommended
candidate at this point is a sample return mission from known spectra
NEOs with a C-type asteroid as the top priority target after Hayabusa s
sample return from the S-type Itokawa in 2010 By best utilizing space
technologies Hayabusa successfully demonstrated and upgrading lessons
learned from the Hayabusa operation in the interplanetary space and in
the vicinity of the asteroid the next minor body mission will be more
scientifically demanding but less technologically challenging than
Hayabusa New challenges include touch-and-go sampling for preserving
depth profile and hydrated minerals and organic compounds underground
Also determining and characterizing sampling sites by both spacecraft
remote sensing and micro rovers carrying the surface science package
become more important for gaining scientific values of returned samples
Once we have actual samples from known S-type and C-type asteroids in
ground laboratories in the next decade we should be able to bridge
taxonomy of asteroids by spectral observation and meteoritic
classifications in the two most major
[show abstract][hide abstract] ABSTRACT: TIGalnNAs-based DQW structures grown at various growth parameters were studied by secondary ion mass spectroscopy (SIMS). Enhanced Tl incorporation could be obtained using TlGaNAs barriers. A direct relationship between the Tl incorporation and N composition is clearly established by the analysis of the effect of growth temperature, growth rate, ECR power and nitrogen flow rate. The Tl incorporation increased with the increase of Tl flux in the case of DQW structures with TlGaAs barriers. In the case of DQW structures with TIGaNAs barriers, the Tl incorporation reached saturation at some Tl flux, indicating the N enhanced higher Tl incorporation.
Indium Phosphide & Related Materials, 2007. IPRM '07. IEEE 19th International Conference on; 06/2007
[show abstract][hide abstract] ABSTRACT: Impact cratering experiments in the microgravity environment were performed using a drop tower. Results indicate the crater formation time and final diameter are not controlled by the gravity scaling.
[show abstract][hide abstract] ABSTRACT: The quinary TlGaInNAs-based double quantum well (DQW) structures were grown on GaAs substrates by electron cyclotron resonance (ECR)-MBE and the samples were probed by secondary ion mass spectroscopy (SIMS). Light emitting diodes (LEDs) were fabricated using these DQW wafers and their electroluminescence (EL) behaviors were studied at different temperatures. The effects of different barrier layers and substrate orientations on the amount of Tl incorporation and on the temperature dependency of the EL peak wavelengths of the LEDs were studied. Higher incorporation of Tl into the quantum well (QW) region and the ensuing change in the temperature dependency of the peak wavelengths owing to the TlGaAs barrier layer are reported. GaAs substrates having (311)B orientation were found to allow more Tl incorporation as compared to (100) and (311)A oriented substrates. The LEDs fabricated out of the TlGaInNAs/TlGaAs/(311)B GaAs DQW structures showed the least temperature dependency of the EL peak wavelengths exemplifying the usefulness of Tl in the QW as well as barrier region.
Journal of Crystal Growth 01/2007; 301:534-538. · 1.55 Impact Factor
[show abstract][hide abstract] ABSTRACT: The spacecraft Hayabusa, which was launched in 2003, arrived at its destination, asteroid (25143) Itokawa in September 2005. The appearance of Itokawa, a small S-type near Earth asteroids, was totally unexpected. The surface is covered with a lot of boulders and there are only a few craters on it. It looks like a contact binary asteroid. The surface composition is quite similar to LL-chondrite. The estimated density is 1.9 ± 0.13 (g/cm3), so the macro-porosity is about 40%. This means that Itokawa is a rubble pile object. In Itokawa, we may see such things that are very close to building blocks of asteroids. In this paper, we review the mission and the first scientific results.
Proceedings of the International Astronomical Union 07/2006; 2:401 - 416.
[show abstract][hide abstract] ABSTRACT: After global observations of asteroid 25143 Itokawa by the Hayabusa spacecraft, we selected the smooth terrain of the Muses Sea for two touchdowns carried out on 19 and 25 November 2005 UTC for the first asteroid sample collection with an impact sampling mechanism. Here, we report initial findings about geological features, surface condition, regolith grain size, compositional variation, and constraints on the physical properties of this site by using both scientific and housekeeping data during the descent sequence of the first touchdown. Close-up images revealed the first touchdown site as a regolith field densely filled with size-sorted, millimeter- to centimeter-sized grains.
[show abstract][hide abstract] ABSTRACT: The near-infrared spectrometer on board the Japanese Hayabusa spacecraft found a variation of more than 10% in albedo and absorption band depth in the surface reflectance of asteroid 25143 Itokawa. Spectral shape over the 1-micrometer absorption band indicates that the surface of this body has an olivine-rich mineral assemblage potentially similar to that of LL5 or LL6 chondrites. Diversity in the physical condition of Itokawa's surface appears to be larger than for other S-type asteroids previously explored by spacecraft, such as 433 Eros.
[show abstract][hide abstract] ABSTRACT: During the interval from September through early December 2005, the Hayabusa spacecraft was in close proximity to near-Earth asteroid 25143 Itokawa, and a variety of data were taken on its shape, mass, and surface topography as well as its mineralogic and elemental abundances. The asteroid's orthogonal axes are 535, 294, and 209 meters, the mass is 3.51 x 10(10) kilograms, and the estimated bulk density is 1.9 +/- 0.13 grams per cubic centimeter. The correspondence between the smooth areas on the surface (Muses Sea and Sagamihara) and the gravitationally low regions suggests mass movement and an effective resurfacing process by impact jolting. Itokawa is considered to be a rubble-pile body because of its low bulk density, high porosity, boulder-rich appearance, and shape. The existence of very large boulders and pillars suggests an early collisional breakup of a preexisting parent asteroid followed by a re-agglomeration into a rubble-pile object.
[show abstract][hide abstract] ABSTRACT: The locations of the pole and rotation axis of asteroid 25143 Itokawa were derived from Asteroid Multiband Imaging Camera data on the Hayabusa spacecraft. The retrograde pole orientation had a right ascension of 90.53 degrees and a declination of -66.30 degrees (52000 equinox) or equivalently 128.5 degrees and -89.66 degrees in ecliptic coordinates with a 3.9 degrees margin of error. The surface area is 0.393 square kilometers, the volume is 0.018378 cubic kilometers with a 5% margin of error, and the three axis lengths are 535 meters by 294 meters by 209 meters. The global Itokawa revealed a boomerang-shaped appearance composed of two distinct parts with partly faceted regions and a constricted ring structure.
[show abstract][hide abstract] ABSTRACT: Images of Itokawa taken by the Hayabusa spacecraft reveal that a
sub-kilometer-sized asteroid can have a significant amount of regolith
over its surface. The regolith of Itokawa is not globally distributed
but partially concentrated only at the smooth terrains.
[show abstract][hide abstract] ABSTRACT: NIRS is a near-infrared spectrometer on-board the spacecraft HAYABUSA
which rendezvoused with the near-earth asteroid 25143 Itokawa in
September through November 2005 HAYABUSA was launched by a Japanese
M-V-5 rocket on May 9 2003 After the Earth swing-by on May 19 2004 the
spacecraft successfully arrived at the Gate Position approximately 20 km
from the asteroid on September 12 2005 During the rendezvous phase with
the asteroid NIRS obtained more than 80 000 spectra of Itokawa The first
spectrum from Itokawa was obtained by NIRS on September 10 and the
distance at that time was 50 km from the asteroid During mission
operations NIRS spectra were obtained at solar phase angles ranging from
near 0 degrees up to 38 degrees and footprint sizes ranging from 6 to 90
m excluding the Touchdown phase of the mission After successfully
arriving at the Gate Position at approximately 20 km from the asteroid
on September 12 we started continuous observations with asteroid
tracking using ONC-W on September 15 simultaneous observations with
AMICA 7-color observations on September 17 and one-dimensional scan
observations by slewing the altitude of the spacecraft on September 24
After switching to the Home Position at an altitude about 7 km from the
asteroid on September 30 we moved the spacecraft to change the
observation aspect angle and solar phase angle to obtain spectra of the
polar regions under different lighting conditions We observed almost the
whole surface of Itokawa during the rendezvous phase of the mission NIRS
found a variation of
[show abstract][hide abstract] ABSTRACT: Hypervelocity impact experiments are carried out with alumina ceramic targets at impact velocities of 2–4 km/s. The fractal dimension (or roughness exponent) of fragment surfaces is estimated by two different methods (different length scales). One is a divider method (large scale) and the other is a gas-absorption one (small scale). The obtained fractal dimensions are different: ∼2.2–2.4 for larger scale and ∼2.5–2.7 for smaller scale. These values are regardless of the degree of fragmentation.
Planetary and Space Science 01/2006; 54(2):212-215. · 2.11 Impact Factor
[show abstract][hide abstract] ABSTRACT: We have fabricated the TlInGaAs quantum well structures on GaAs(100) substrates and demonstrated the electroluminescence (EL) emission up to 300K. Compared with the InGaAs quantum well reference samples, we confirmed that the temperature-variation of EL peak energy was decreased by the addition of Tl into InGaAs. We also demonstrated the pulsed current injection laser oscillation for the TlInGaAs/GaAs double quantum wells laser diodes with InGaP layers as cladding layers.
Indium Phosphide and Related Materials, 2005. International Conference on; 06/2005
[show abstract][hide abstract] ABSTRACT: NIRS is a near infrared spectrometer on-board the spacecraft Hayabusa. After the launch, we performed the observations of some bright stars and planets in the cruising phase toward the asteroid. We report the results of these observations.
[show abstract][hide abstract] ABSTRACT: NIRS is a near infrared spectrometer on-boarded the spacecraft HAYABUSA (MUSESC), which aims to return samples from a near-earth asteroid, (25143) Itokawa (1998 SF36). HAYABUSA was successfully launched by Japanese M-V-5 rocket on May 19, 2003. After the earth swing-by in Jun 2004, the spacecraft will arrive at the asteroid in summer 2005. During the rendezvous phase with the asteroid, we will observe the asteroid surface using NIRS and obtain reflectance spectra of the surface materials across the wavelength range of 850nm to 2100nm. Based on ground-based observations ,,, (25143) Itokawa appears to be an S(IV) type asteroid. NIRS can detect absorption bands due to olivine and pyroxene and investigate the mineralogical composition of the surface materials. Combining with the data from asteroid multiband imaging camera (AMICA) and X-ray spectrometer (XRS), we can reveal a relationship between asteroids and meteorites.
[show abstract][hide abstract] ABSTRACT: On the 9th May 2003 JST, Japanese spacecraft MUSES-C was successfully launched from Uchinoura. The spacecraft was directly inserted to interplanetary trajectory and renamed as Hayabusa , or "Falcon" to be the world s first sample return spacecraft to a near Earth asteroid (NEA). The NEA (25143)Itokawa (formerly known as "1998SF36") is its mission target. Its orbital and physical characteristics were well observed; the size is (490 +/- 100)x (250 +/- 55)x(180 +/- 50) m with about 12-hour rotation period. It has a red-sloped S(IV)-type spectrum with strong 1- and 2-micron absorption bands, analogous to ordinary LL chondrites with space weathering effect. Assuming its bulk density, the surface gravity level of Itokawa is in the order of 10 micro-G with its escape velocity = approx. 20 cm/s.