Magnetic Cleanliness Program Under Control of Electromagnetic Compatibility for the SELENE (Kaguya) Spacecraft

To achieve the scientific objectives related to the lunar magnetic field measurements in a polar orbit at an altitude of 100 km, strict electromagnetic compatibility (EMC) requirements were applied to all components and subsystems of the SELENE (Kaguya) spacecraft. The magnetic cleanliness program was defined as one of the EMC control procedures, and magnetic tests were carried out for most of the engineering and flight models. The EMC performance of all components was systematically controlled and examined through a series of EMC tests. As a result, the Kaguya spacecraft was made to be very clean, magnetically. Hence reliable scientific data related to the magnetic field around the Moon were obtained by the LMAG (Lunar MAGnetometer) and the PACE (Plasma energy Angle and Composition Experiment) onboard the Kaguya spacecraft. These data have been available for lunar science use since November 2009.     

Correlations between changes in electrical parameters and changes in cell elongation rates in gravistimulated roots.

The earliest changes in growth rate following the gravistimulation of roots occur in a special group of cells between the meristem and the elongating region of the root. This zone is called the postmitotic isodiametric growth (PIG) zone and consists of cells which have ceased dividing and are expanding isodiametrically. Upon gravistimulation cells along the upper side of the PIG zone begin elongating rapidly and this accounts for much of the early growth asymmetry. There is rapid (< 30 s) hyperpolarization of cells on the upper side of the PIG zone as well as rapid uptake of potassium from the stele. We propose that there is a relationship between the rate of hydrogen ion efflux and the extent of membrane hyperpolarization in the PIG zone and that such changes in potential are an early indication of impending changes in growth performance. Although the development of auxin asymmetry in the cap and its transmission to the elongating region is considered to be the controlling factor in root gravitropism, auxin asymmetry in the cap develops only after 30 min, about the same as the lag before initiation of curvature. Although this dilemma may be partly resolved by the location of the PIG zone close to the cap, alternative explanations such as gravi-detection by the PIG zone or very rapid (electrical?) signal transmission from the cap to the PIG zone need to be considered.     

Thermal properties of molten InSb,GaSb, and InxGa1−xSb alloy semiconductor materials in preparation for crystal growth experiments on the international space station

The thermal properties of InSb, GaSb and In_xGa_1−xSb, such as the viscosity, wetting property, and evaporation rate, were investigated in preparation for the crystal growth experiment on the International Space Station (ISS). The viscosity of InGaSb, which is an essential property for numerical modeling of crystal growth, was evaluated. In addition, the wetting properties between molten In_xGa_1−xSb and quartz, BN, graphite, and C-103 materials were investigated. The evaporation rate of molten In_xGa_1−xSb was measured to determine the affinity of different sample configurations. From the measurements, it was found that the viscosity of In_xGa_1−xSb was between that of InSb and GaSb. The degree of wetting reaction between molten In_xGa_1−xSb and the C-103 substrate was very high, whereas that between molten In_xGa_1−xSb and quartz, BN, and graphite substrates was very low. The results suggest that BN and graphite can be used as materials to cover InSb and GaSb samples inside a quartz ampoule during the microgravity experiments. In addition, the difference of the evaporation rate of molten In_xGa_1−xSb, GaSb, and InSb was small at low, and large at high temperature.     

Numerical simulations of the regional characteristics of dust transport on Mars

Using a Martian general circulation model (GCM), regions favorable for expansion of dust storms on Mars are identified. Dust transport simulations for the northern fall provide global maps of dust expansibility. These global maps show that dust injected from certain areas in the northern mid-latitudes tends to spread widely within a few days. The high expansibility of dust in such areas results from thermal tides, baroclinic waves, and quasi-stationary disturbances. Dust injected into the vast regions around Tharsis and the Sirenum–Aonia regions also tends to spread extensively. However, dust expansion around these two regions largely depends on the local time of dust injection. On the other hand, dust injected at high latitudes in either hemisphere does not spread extensively. Such global maps indicating regions favorable for dust storm expansion are a clue to understanding the expansion processes and climatology of great dust storms on Mars.     

JUXTA: A new probe of X-ray emission from the Jupiter system

For the future Japanese exploration mission of the Jupiter’s magnetosphere (JMO: Jupiter Magnetospheric Orbiter), a unique instrument named JUXTA (Jupiter X-ray Telescope Array) is being developed. It aims at the first in-situ measurement of X-ray emission associated with Jupiter and its neighborhood. Recent observations with Earth-orbiting satellites have revealed various X-ray emission from the Jupiter system. X-ray sources include Jupiter’s aurorae, disk emission, inner radiation belts, the Galilean satellites and the Io plasma torus. X-ray imaging spectroscopy can be a new probe to reveal rotationally driven activities, particle acceleration and Jupiter–satellite binary system. JUXTA is composed of an ultra-light weight X-ray telescope based on micromachining technology and a radiation-hard semiconductor pixel detector. It covers 0.3–2 keV with the energy resolution of <100 eV at 0.6 keV. Because of proximity to Jupiter (∼30 Jovian radii at periapsis), the image resolution of <5 arcmin and the on-axis effective area of >3 cm² at 0.6 keV allow extremely high photon statistics and high resolution observations.     

Overview of Differential VLBI Observations of Lunar Orbiters in SELENE (Kaguya) for Precise Orbit Determination and Lunar Gravity Field Study

The Japanese lunar explorer SELENE (Kaguya), which was launched on September 14th, 2007, was the target of VLBI observations over the period November 2007 to June 2009. These observations were made in order to improve the lunar gravity field model, in particular the lower degree coefficients and the model near the limb. Differential VLBI Radio sources, called VRAD instruments, were on-board the subsatellites, Rstar (Okina) and Vstar (Ouna), and the radio signals were observed by the Japanese VERA (VLBI Exploration of Radio Astrometry) network, and an international VLBI network. Multi-frequency and same-beam VLBI techniques were utilized and were essential aspects of the successful observing program. Multi-frequency VLBI was employed in order to improve the accuracy of the orbit determination obtained from the phase delay from the narrow-band satellite signals, while the same-beam VLBI method was used to resolve the cycle ambiguity which is inherent in the multi-frequency VLBI method. The observations were made at three S-band frequencies (2212, 2218 and 2287 MHz), and one X-band frequency (8456 MHz). We have succeeded in correlating the recorded signals from Okina/Ouna, and we obtained phase delays with an accuracy of several pico-seconds at S-band.     

Design and Performance of the ICON EUV Spectrograph

We present the design, implementation, and on-ground performance measurements of the Ionospheric Connection Explorer EUV spectrometer, ICON EUV, a wide field (\(17^{\circ}\times 12^{\circ}\)) extreme ultraviolet (EUV) imaging spectrograph designed to observe the lower ionosphere at tangent altitudes between 100 and 500 km. The primary targets of the spectrometer, which has a spectral range of 54–88 nm, are the Oii emission lines at 61.6 nm and 83.4 nm. Its design, using a single optical element, permits a $0\stackrel{{}^{°}}{.}26$ imaging resolution perpendicular to the spectral dispersion direction with a large (\(12^{\circ} \)) acceptance parallel to the dispersion direction while providing a slit-width dominated spectral resolution of \(R\sim25\) at 58.4 nm. Pre-flight calibration shows that the instrument has met all of the science performance requirements.     

VLBI for better gravimetry in SELENE

The Japanese lunar explorer SELENE (SElenological and Engineering Explorer), to be launched in 2007, will for the first time utilize VLBI observations in lunar gravimetry investigations. This will particularly improve the accuracy to which the low degree gravitational harmonics and the gravity field near the limb can be measured, and when combined with Doppler measurements will enable three-dimensional information to be extracted. Differential VLBI Radio sources called VRAD experiment involves two on-board sub-satellites, Rstar and Vstar. These will be observed using differential VLBI to measure the trajectories of the satellites with the Japanese network named VERA (VLBI Exploration of Radio Astrometry) and an international VLBI network.