Multimodal characteristics of a piezoelectric lead zirconate titanate element impacted with iron particles having velocities above 20 km/s

The responses of a piezoelectric lead zirconate titanate (PZT) element to hypervelocity collisions were experimentally studied. In this study, the particles of masses ranging from 0.3 to 10 fg were made to collide with PZT at velocities between 20 and 96 km/s. The amplitude and the corresponding rise time of the single-pulse output signals that were produced in the piezoelectric PZT element were measured to determine the possible collision states. The results revealed an apparently multimodal output; three classes were assumed to be involved in the pulse formation mechanism. The amplitude and rise time were sensitive to the collision velocity. The multimodal behavior implied that the PZT-based cosmic dust detectors should be calibrated according to the class they belong to.     

Current status of X-ray spectrometer development in the SELENE project

The X-ray spectrometer (XRS) on the SELENE (SELenological and ENgineering Explorer) spacecraft, XRS, will observe fluorescent X-rays from the lunar surface. The energy of the fluorescent X-ray depends on the elements of which the lunar soil consists, therefore we can determine elemental composition of the upper most lunar surface. The XRS consists of three components: XRF-A, SOL-B, and SOL-C. XRF-A is the main sensor to observe X-rays from the lunar surface. SOL-B is direct monitor of Solar X-ray using Si-PIN photodiode. SOL-C is another Solar X-ray monitor but observes the X-rays from the standard sample attached on the base plate. This enables us to analyze by a comparative method similar to typical laboratory XRF methods. XRF-A and SOL-C adopt charge coupled device as an X-ray detector which depletion layer is deep enough to detect X-rays. The X-ray spectra were obtained by the flight model of XRS components, and all components has been worked well to analyze fluorescent X-rays. Currently, development of the hardware and software of the XRS has been finished and we are preparing for system integration test for the launch.     

Structure and thermal control of panel extension satellite (PETSAT)

Panel ExTension SATellite (PETSAT) [S. Nakasuka, Y. Nakamura, Panel extension satellite (PETSAT)—a novel satellite concept consisting of modular, functional and plug-in panels, in: 24th International Symposium on Space Technology and Science, invited talk, 2004-o-2, 2004 [1]] is a satellite which is made of several “functional panels”. Each panel has a special dedicated function and various combinations of different kinds of functional panels enable PETSAT to deal with various mission requirement. Development of PETSAT requires four interface requirements. These are mechanical interface, thermal interface, electrical interface and information interface. In this paper, mechanical interface and thermal interface of PETSAT are especially focused on and introduced. In the development of PETSAT issues about mechanical interface corresponds to panel structure and deployment mechanism. The structure of PETSAT is designed so as to have light weigh, enough space for devices and high stiffness. And deployment system has simple mechanism to avoid vacuum metalizing and improve reliability. On the other hand, approaches for thermal interface [K. Higashi, S. Nakasuka, Y. Sugawara, H. Sahara, K. Koyama, C. Kobayashi, T. Okada, Thermal control of panel extension satellite (PETSAT), in: 25th International Symposium on Space Technology and Science, 2006-j-02, 2006 [2]] are homogenization of temperature within panel and between panels. Homogenization of temperature within panels can be realized by heat lane plate, and that between panels is realized by magnetic fluid loop with magnetic heat pump. These approaches for mechanical and thermal interface are demonstrated in SOHLA-2 [Y. Sugawara, S. Nakasuka, T. Eishima, H. Sahara, Y. Nakamura, K. Koyama, C. Kobayashi, T. Okada, Elemental technologies for realization of panel extension satellite (PETSAT), in: 25th International Symposium on Space Technology and Science, 2006-J-01, 2006 [3]] that is satellite of technology demonstration for PETSAT.     

Laboratory calibration measurements of a piezoelectric lead zirconate titanate cosmic dust detector at low velocities

A cosmic dust monitor for use onboard a spacecraft is currently being developed using a piezoelectric lead zirconate titanate element (PZT). Its characteristics of the PZT sensor is studied by ground-based laboratory impact experiments using hypervelocity particles supplied by a Van de Graaff accelerator. The output signals obtained from the sensor just after the impact appeared to have a waveform that was explicitly related to the particle’s impact velocity. For velocities less than ∼6 km/s, the signal showed an oscillation pattern and the amplitude was proportional to the momentum of the impacting particle. For higher velocities, the signal gradually changed to a single waveform. The rise time of this single waveform was proportional to the particle’s velocity for velocities above ∼6 km/s. The present paper reports on results for the low velocity case and especially discusses the effect of an outer coating of the sensor with a paint, which is used to reduce heating by solar radiation.     

Japanese research project on Arctic and Antarctic observations of the middle atmosphere

An all-sky optical imager is in routine observation at the South Pole. Monochromatic images of aurora and air glow at N₂⁺ 427.8nm, OI 557.7nm, OI 630nm and OH 730nm are supplying significant information on the magnetospheric process in the polar cap and cusp/cleft region along with atmospheric wave signature at this particular point. SuperDARN radars in Antarctica make observations over the South Pole.

At Syowa Station, Antarctica, a multi-instrumental observation project is now being implemented for the study of the polar upper atmosphere from the mesosphere to the thermosphere, where complex physical and chemical processes take place making the region very attractive for scientific research. Two HF radars, which are part of SuperDARN radars, have been already installed and started observations. By the end of 1999, all-sky imagers, photo meters, a Na temperature Lidar, an MF radar and a Fabry-Perot interferometer will be introduced and start collecting various physical parameters on a routine basis.

In the Arctic region, we are planning to deploy coordinated ground-based observations with optical, radio and radar sensing of the polar middle and upper atmosphere in conjunction with EISCAT radars. Scientific goals are versatile to shed light on the tangled coupling processes in response to magnetospheric disturbances from above and bi-lateral interactions with high-density lower atmospheric layers. These are outlined in this paper.     

A balloon-borne very long baseline interferometry experiment in the stratosphere: Systems design and developments

The balloon-borne very long baseline interferometry (VLBI) experiment is a technical feasibility study for performing radio interferometry in the stratosphere. The flight model has been developed. A balloon-borne VLBI station will be launched to establish interferometric fringes with ground-based VLBI stations distributed over the Japanese islands at an observing frequency of approximately 20?GHz as the first step. This paper describes the system design and development of a series of observing instruments and bus systems. In addition to the advantages of avoiding the atmospheric effects of absorption and fluctuation in high frequency radio observation, the mobility of a station can improve the sampling coverage (“uv-coverage”) by increasing the number of baselines by the number of ground-based counterparts for each observation day. This benefit cannot be obtained with conventional arrays that solely comprise ground-based stations. The balloon-borne VLBI can contribute to a future progress of research fields such as black holes by direct imaging.     

Characteristics of piezoelectric lead zirconate titanate multilayered detector bombarded with hypervelocity iron particles

A cosmic dust detector is currently being developed using a piezoelectric lead zirconate titanate (PZT) element. The characteristics of the multilayered detector (MD), which was composed of one hundred PZT disks, were investigated by bombarding it with hypervelocity iron particles supplied by a Van de Graaff accelerator. It was confirmed that there was a linear relationship between the signal amplitude observed from MD and the momentum of the particles. As compared with the single-layered detector (SD) that was composed of one PZT disk, it was found that the sensitivity of MD was ∼3 times higher than that of SD within the limits of the experimental conditions.     

Possible Suzaku detection of non-thermal X-ray signals from a rotating magnetized white dwarf

Although rotating neutron stars (NSs) have been regarded as being textbook examples of astrophysical particle acceleration sites for decades, details of the acceleration mechanism remain a mystery; for example, we cannot yet observationally distinguish “polar cap” models from “outer gap” models. To solve the model degeneracy, it is useful to study similar systems with much different physical parameters. Strongly magnetized white dwarfs (WDs) are ideal for this purpose, because they have essentially the same system geometry as NSs, but differ largely from NSs in the system parameters, including the size, magnetic field, and the rotation velocity, with the induced electric field expected to reach 10¹³–10¹⁴ eV. Based on this idea, the best candidate among WDs, AE Aquarii, was observed with the fifth Japaneses X-ray satellite, Suzaku. The hard X-ray detector (HXD) on-board Suzaku has the highest sensitivity in the hard X-ray band over 10 keV. A marginal detection in the hard X-ray band was achieved with the HXD, and was separated from the thermal emission. The flux corresponds to about 0.02% of its spin-down energy. If the signal is real, this observation must be a first case of the detection of non-thermal emission from WDs.     

Sensitivity Reduction by Double Perfect Model Following

We propose a double perfect model following (DPMF) system which uses two models: one is used to define the desirable response and the other is used to reduce sensitivity to parameter perturbation. The concept is shown and methods of model selection and controller synthesis are discussed, followed by numerical examples and an aircraft control example which demonstrate performance of the DPMF concept. It is shown that the DPMF system can be less sensitive than a nominally equivalent single perfect model following (SPMF) system and that sensitivity reduction is enhanced by proper selection of the model. It is also shown that the sensitivity of multiinput systems can be reduced componentwise or blockwise by using a decoupled type model.     

Microbial survival: the paleome: a sedimentary genetic record of past microbial communities

Molecular genetic methods were used to analyze the remnants of microbial ecosystems contained within an ancient oceanic microbial habitat that was recovered from a continental drilled core of black shale approximately 100 million years in age. Bacterial ribosomal RNA genes were vertically amplified from the six different depths of a black shale core associated with a phosphate-rich stratum, defined as one of the mid-Cretaceous oceanic anoxic events (OAEs). Although the black shale core was recovered from a terrestrial coring effort, the recovered 16S rRNA gene sequences showed affinity to microbial communities previously seen in deep-sea sedimentary environments (i.e., the microbial assemblage was easily recognizable as a marine community). In particular, a number of 16S rRNA gene clones of oceanic sulfate-reducing bacteria within the delta-Proteobacteria predominated at the OAE layer. The recovered bacterial DNA signatures are consistent with the interpretation that the sequences are derived from the past microbial communities buried in either sea-bottom or subseafloor environments during the sedimentation process and, after ceasing growth, preserved until the present.