Takumi ABE

第29回大気圏シンポジウム（2016年3月7日-8日. 宇宙航空研究開発機構宇宙科学研究所（JAXA)(ISAS)）, 相模原市, 神奈川県 29th Atmospheric Science Symposium (March 7-8, 2016. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan 資料番号: SA6000051049 レポート番号: VI-5

平成27年度宇宙科学に関する室内実験シンポジウム (2016年2月23日-24日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県 2016 Symposium on Laboratory Experiment for Space Science (July 23-24, 2016. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan 資料番号: SA6000055011

大気球シンポジウム 平成26年度（2014年11月6-7日. 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)）, 相模原市, 神奈川県 Balloon Symposium 2014 (November 6-7, 2014. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan 資料番号: SA6000021028 レポート番号: isas14-sbs-028

平成23年度スペースプラズマ研究会・講演集. 2012年2月27日～2012年2月28日. 宇宙航空研究開発機構宇宙科学研究所.

Lithium ejection system (LES) is one of the chemical payloads for the ionosphere observation. Lithium is selected as the chemical tracer to detect optically the neutral winds, and the thermite loaded in LES played a role of the heat sauce to vaporize the solid phase lithium. This device has been launched by the Japanese sounding rocket, S-520, from Uchinoura space center in 2007. Gaseous lithium was successfully injected into the space, and the red colored cloud was able to be observed from the ground. The concept was explained in early papers, and their design was shown that the thermite including lithium or sodium pellets was directly charged in the canister. Thermite is ignited by the pyrotechnics and generates the high temperature chemical products which give the vaporization energy of the released materials. The payload design was considered that the instruments on board which acts by the pyrotechnics need to be equipped with the safe and arm device (SAD) from the safety standard. The final design obtained the safety and the reliability of this device for storing and handling. Lithium in the canister is able to be removed with ease, and the tracer materials will be able to replace lithium to other one if necessary. 13 LES canisters were fabricated for ISAS-NASA international collaborative space science mission. This paper reports the results of the design study and the specification of LES.

The primary objectives of the sounding rocket experiment, S-520-25, are to deploy an electro-conductive bare tape tether in space and to study the electron current-collection by the tape tether when biased positively. Before the space experiment, we have carried out laboratory experiments on the plasma collection by the tape tether in a large space science chamber at ISAS/JAXA. This paper presents the major results on the currentvoltage characteristics of the tape tether in the plasma environment which simulates the ionospheric plasma It was found that the tether current approached to the prediction by the Orbit Motion Limit (OML) theory as the tether voltage was increased up to 500 V. In the high voltage region more than 200 V, we often observed the discharge at the surface of the tether that damaged the tether material.

Pressure measurements in scientifi c balloon and sounding rocket experiments in the upper atmosphere are technologically and scientifi cally important. An onboard small pressure gauge developed in this study is the quartz friction gauge, which is based on the principle that the resonance impedance of a quartz oscillator varies with the pressure of ambient gas. The gauge has a wide measuring range (10^5 - 10^<-2> Pa), which corresponds to the atmospheric pressure from the ground to an altitude of about 100 km. The sensor part and data processing part weigh 100 g and 200 g, respectively. In addition, power consumption of less than 1 W is achieved with this gauge. The gauge is suited for high altitude balloon experiments because the weight of their instruments is severely limited. A tuningfork-shaped quartz oscillator in the gauge is widely used for wrist watches and the structure has a high resistance to vibration and shock, and thus the gauge is applicable to sounding rocket experiments that require onboard instruments to have high environment resistance. In this paper, we report on a performance demonstration test of the newly developed quartz friction gauge using the BU30-5 balloon experiment.

The Venus Climate Orbiter mission (PLANET-C), one of the future planetary missions of Japan, aims at understanding the atmospheric circulation of Venus. Meteorological information will be obtained by globally mapping clouds and minor constituents successively with 4 cameras at ultraviolet and infrared wavelengths, detecting lightning with a high-speed imager, and observing the vertical structure of the atmosphere with radio science technique. The equatorial elongated orbit with westward revolution fits the observation of the movement and temporal variation of the atmosphere which rotates westward. The systematic, continuous imaging observations will provide us with an unprecedented large dataset of the Venusian atmospheric dynamics. Planet-C will be launched in 2010 and will reach Venus in 5 months. Nominal operation period is 2 earth years.

We present proposals for observing the plasma transportation and circulation processes and the dynamics of the thermal plasmas that are the important element on Venus ionosphere by instruments installed on Venus Climate Orbiter. Main purpose of the observation is to elucidate the following unresolved problems: 1) How the upper atmosphere interacts with the lower atmosphere. 2) How much the energy of the solar wind can enter to the Venus upper atmosphere. 3) How momentum and energy of particles are transported into the upper atmosphere from external regions through the coupling process. In the presentation, the observation target and strategy will be discussed in detail.

The dynamics of neutral atmosphere is closely coupled with the behavior of ionized gas and chemical process in the lower thermosphere-mesosphere region. The measurement of the neutral wind at the height region is important to study those processes. So far the neutral wind has been independently measured by a radar-tracking of foil chaffs: a micro rocket is needed for the wind measurement in addition to a main, big rocket which carries other scientific instruments. In order to conduct simultaneous wind and other measurements onboard a single rocket, we have developed two types of foil chaff ejection systems to be installed in a sounding rocket. We have tested two foil chaff ejection systems: 1) foil chaffs are accommodated in an airtight cylinder case whose sealing cap is removed with one atmospheric pressure, 2) foil chaffs are accommodated in the splitted cylinder, which is ejected by a spring. These two ejection systems were loaded on a sounding rocket S-310-29, which was launched on the 10th, January, 2000. About 20,000 pieces of foil chaff in total were successfully ejected during the downleg of the rocket, around the height of 100km, 341sec after the launch. The foil chaff were tracked in the height range of 95.0-88.5km by the primary radar and the velocity and direction of the neutral wind were obtained.

記事種別: 会議・学会報告・シンポジウム

Mid-lattitude sporadic E (Es) layers have been observed for a long time and the formation mechanism based on the wind shear theory is currently acceptd among the science community. However, no satisfactory theory which discusses the energetics of the Es layer exists because of the lack of the accurate electron temperature measurement. v-i characteristic curves were obtained by means of a glass-sealed Langmuir probe onboard the rocket S-310-27 which was launched on the 25th, January, 1998. Detail study of the v-i characteristic curves clearly shows the effect of the secondary electrons from the electrode surface, which should be taken into account to derive the accurate daytime electron density from the ion-current region of the v-i characteristic curve. The careful analysis of the ion current shows the wavy structure in the height profile, which is concluded to be produced by the internal gravity wave. The electron temperature in the Es peak which appeared at the height of 92-93km was about 500K higher than of the possible netral temperature (about 200K). In this report, we will discuss the reliability of these results and provide the basic informations to study the energetics of the Es in the future studies.

We already realized the transparent wave absorver using resistive-film at 60 GHz. The necessity of transparent wave absorber at X band for radars is increasing. In this paper, we try to realize the two-layered transparent wave absorber using resistive-film at X band. As a result, we can show the design charts as the function of dielectric constant and thickness of glass, and can confirm that the transparent wave absorber has the reflection loss of more than 17dB at 8.5〜11.5 [GHz].

We present a possible suggestion method to measure a permittivity of material without cutting a sample by means of the rectangular cavity resonator. A theoretical discussion on the possibility is given in this paper by studying the relationship between the material permittivity and a resonance frequency of the electromagnetic field inside cavity which is calculated by the FDTD method. We show the permittivity measurement chart by which the permittivity can be estimated from the measured resonant frequency. The permittivity estimated has a reasonable agreement with an empirical value within an error of several percents. The present result supports the validity of the present method.

In this paper, the author discusses the error due to deformation of sample on permittivity measurement by standing-wave method on rectangular waveguide using Finite Difference Time Domain. The analytical model is considered the samples of four different deformed cases; (1) undeformed and no-loss sample, (2) undeformed and lossy sample, (3) deformed and no-loss sample, and (4) deformed and lossy sample. <br>As a result, it is confirmed that a deformation of the sample has strong influence on an accuracy of complex permittivity measurement. Specifically, the auther presents an interesting relation between the measurement error and the degree of sample deformation, including quantitative value of the error as a function of geometrical relation of the sample deformation with respect to the electric field distribution.