Publishing type：Research paper (scientific journal)  

We have carried out ground-based NIRAS (Near-InfraRed Aurora and airglow Spectrograph) observations at Syowa station, Antarctic (69. 0 S , 39. 6 E) and Kiruna (67. 8 N , 20. 4 E), Sweden for continuous measurements of hydroxyl (OH) rotational temperatures and a precise evaluation of auroral contaminations to OH Meinel (3,1) band. A total of 368-nights observations succeeded for 2 winter seasons, and 3 cases in which N2+ Meinel (1,2) band around 1.5μm was significant were identified. Focusing on two specific cases, detailed spectral characteristics with high temporal resolutions of 30 s are presented. Intensities of N2+ band were estimated to be 228 kR and 217 kR just at the moment of the aurora breakup and arc intensification during pseudo breakup, respectively. At a wavelength of P (2) line (∼1523nm), N2+ emissions were almost equal to or greater than the OH line intensity. On the other hand, at a wavelength of P (4) line (∼1542nm), the OH line was not seriously contaminated and still dominant to N2+ emissions. Furthermore, we evaluated N2+ (1,2) band effects on OH rotational temperature estimations quantitatively for the first time. Auroral contaminations from N2+ (1,2) band basically lead negative bias in OH rotational temperature estimated by line-pair-ratio method with P (2) and P (4) lines in OH (3,1) band. They possibly cause underestimations of OH rotational temperatures up to 40 K. In addition, N2+ (1,2) band contaminations were temporally limited to a moment around the aurora breakup. This is consistent with proceeding studies reporting that enhancements of N2+ (1,2) band were observed associated with International Brightness Coefficient 2–3 auroras. It is also suggested that the contaminations would be neglected in the polar cap and the sub-auroral zone, where strong aurora intensification is less observed. Further spectroscopic investigations at these wavelengths are needed especially for more precise evaluations of N2+ (1,2) band contaminations. For example, simultaneous 2-D imaging observation and spectroscopic measurement with high spectral resolutions for airglow in OH (3,1) band will make great advances in more robust temperature estimations in the auroral zone.[Figure not available: see fulltext.]. ∘ ∘ ∘ ∘ 1 1 1 1

DOI： 10.1186/s40623-021-01360-0

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

The brightness temperature of the Venus disk obtained by Longwave Infrared Camera (LIR) on board Akatsuki shows clear limb darkening at low and middle latitudes. The profile of limb brightness reflects the vertical distributions of atmospheric temperature and the optical thickness of the cloud particles. Horizontal distributions of brightness temperature obtained by LIR during ∼5.8 Venusian years were analyzed to investigate the vertical structure of the brightness temperature distribution above the cloud tops based on the emission angle dependence of the sensing altitude. Emission angles were converted to sensing altitudes by a radiative transfer calculation with nominal temperature and cloud particle distributions based on past observations. We show a local time-altitude cross section of the brightness temperature deviation above the cloud tops for three latitudinal zones. The derived vertical amplitude distribution of the diurnal and semidiurnal tides above ∼68 km is mostly explained by the classical theory of thermal tides. A semidiurnal tide in which the phase shifts upstream with altitude is clearly seen in the equatorial region. By applying the dispersion relation of the internal gravity wave to the observed wave structure, it was found that the zonally averaged zonal wind velocity at altitudes of 66–71 km was approximately the same as the known superrotation velocity. By comparing the observed and simulated vertical phase structures, it is suggested that the tidal wave structure seen in the equatorial cloud tops is an aspect of upward propagation of a gravity wave generated in the upper cloud layer by solar heating.

DOI： 10.1029/2020JE006808

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Publishing type：Research paper (scientific journal)  

Although Venus is a terrestrial planet similar to Earth, its atmospheric circulation is much different and poorly characterized1. Winds at the cloud top have been measured predominantly on the dayside. Prominent poleward drifts have been observed with dayside cloud tracking and interpreted to be caused by thermal tides and a Hadley circulation2–4; however, the lack of nightside measurements over broad latitudes has prevented the unambiguous characterization of these components. Here we obtain cloud-tracked winds at all local times using thermal infrared images taken by the Venus orbiter Akatsuki, which is sensitive to an altitude of about 65 kilometres5. Prominent equatorward flows are found on the nightside, resulting in null meridional velocities when these are zonally averaged. The velocity structure of the thermal tides was determined without the influence of the Hadley circulation. The semidiurnal tide was found to have an amplitude large enough to contribute to the maintenance of the atmospheric superrotation. The weakness of the mean meridional flow at the cloud top implies that the poleward branch of the Hadley circulation exists above the cloud top and that the equatorward branch exists in the clouds. Our results should shed light on atmospheric superrotation in other celestial bodies.

DOI： 10.1038/s41586-021-03636-7

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Planetesimals—the initial stage of the planetary formation process—are considered to be initially very porous aggregates of dusts<SUP>1,2</SUP>, and subsequent thermal and compaction processes reduce their porosity<SUP>3</SUP>. The Hayabusa2 spacecraft found that boulders on the surface of asteroid (162173) Ryugu have an average porosity of 30-50% (refs. <SUP>4-6</SUP>), higher than meteorites but lower than cometary nuclei<SUP>7</SUP>, which are considered to be remnants of the original planetesimals<SUP>8</SUP>. Here, using high-resolution thermal and optical imaging of Ryugu's surface, we discovered, on the floor of fresh small craters (&lt;20 m in diameter), boulders with reflectance (~0.015) lower than the Ryugu average<SUP>6</SUP> and porosity &gt;70%, which is as high as in cometary bodies. The artificial crater formed by Hayabusa2's impact experiment<SUP>9</SUP> is similar to these craters in size but does not have such high-porosity boulders. Thus, we argue that the observed high porosity is intrinsic and not created by subsequent impact comminution and/or cracking. We propose that these boulders are the least processed material on Ryugu and represent remnants of porous planetesimals that did not undergo a high degree of heating and compaction<SUP>3</SUP>. Our multi-instrumental analysis suggests that fragments of the highly porous boulders are mixed within the surface regolith globally, implying that they might be captured within collected samples by touch-down operations<SUP>10,11</SUP>....

DOI： 10.1038/s41550-021-01371-7

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Other Link： https://www.nature.com/articles/s41550-021-01371-7

Publishing type：Research paper (scientific journal)   Publisher：Japan Society for Aeronautical and Space Sciences  

DOI： 10.2322/tastj.19.654

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.icarus.2020.113835

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Association for the Advancement of Science (AAAS)  

DOI： 10.1126/science.aaz4439

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Carbonaceous (C-type) asteroids(1) are relics of the early Solar System that have preserved primitive materials since their formation approximately 4.6 billion years ago. They are probably analogues of carbonaceous chondrites(2,3) and are essential for understanding planetary formation processes. However, their physical properties remain poorly known because carbonaceous chondrite meteoroids tend not to survive entry to Earth's atmosphere. Here we report on global one-rotation thermographic images of the C-type asteroid 162173 Ryugu, taken by the thermal infrared imager (TIR)(4) onboard the spacecraft Hayabusa2(5), indicating that the asteroid's boulders and their surroundings have similar temperatures, with a derived thermal inertia of about 300 J m(-2) s(-0.5) K-1 (300 tiu). Contrary to predictions that the surface consists of regolith and dense boulders, this low thermal inertia suggests that the boulders are more porous than typical carbonaceous chondrites(6) and that their surroundings are covered with porous fragments more than 10 centimetres in diameter. Close-up thermal images confirm the presence of such porous fragments and the flat diurnal temperature profiles suggest a strong surface roughness effect(7,8). We also observed in the close-up thermal images boulders that are colder during the day, with thermal inertia exceeding 600 tiu, corresponding to dense boulders similar to typical carbonaceous chondrites(6). These results constrain the formation history of Ryugu: the asteroid must be a rubble pile formed from impact fragments of a parent body with microporosity(9) of approximately 30 to 50 per cent that experienced a low degree of consolidation. The dense boulders might have originated from the consolidated innermost region or they may have an exogenic origin. This high-porosity asteroid may link cosmic fluffy dust to dense celestial bodies(10).Thermal imaging data obtained from the spacecraft Hayabusa2 reveal that the carbonaceous asteroid 162173 Ryugu is an object of unusually high porosity.

DOI： 10.1038/s41586-020-2102-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

The reason for stationary gravity waves at Venus’ cloud top to appear mostly at low latitudes in the afternoon is not understood. Since a neutral layer exists in the lower part of the cloud layer, the waves should be affected by the neutral layer before reaching the cloud top. To what extent gravity waves can propagate vertically through the neutral layer has been unclear. To examine the possibility that the variation of the neutral layer thickness is responsible for the dependence of the gravity wave activity on the latitude and the local time, we investigated the sensitivity of the vertical propagation of gravity waves on the neutral layer thickness using a numerical model. The results showed that stationary gravity waves with zonal wavelengths longer than 1000 km can propagate to the cloud-top level without notable attenuation in the neutral layer with realistic thicknesses of 5–15 km. This suggests that the observed latitudinal and local time variation of the gravity wave activity should be attributed to processes below the cloud. An analytical approach also showed that gravity waves with horizontal wavelengths shorter than tens of kilometers would be strongly attenuated in the neutral layer; such waves should originate in the altitude region above the neutral layer.

DOI： 10.1186/s40623-019-1106-7

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Other Link： http://link.springer.com/article/10.1186/s40623-019-1106-7/fulltext.html

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union ({AGU})  

DOI： 10.1029/2019GL083820

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Language：English   Publishing type：Research paper (bulletin of university, research institution)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union ({AGU})  

DOI： 10.1029/2018JE005842

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1126/science.aaw0422

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Lunar and Planetary Institute  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：International Astronautical Federation, IAF  

SIHLA is a small satellite mission proposed as a Mission of Opportunity to NASA for flight on the same launch opportunity as the NASA IMAP mission. SIHLA is a free-flyer that is carried into a transfer orbit on the ESPA-Grande ring. The SIHLA spacecraft flies independently to the L1 point where it will orbit and perform its science mission. From there, SIHLA will map the distribution of H in the heliosphere. From the L1 point, outside of the Earth's atmosphere and H exosphere, SIHLA is able to map the sky without the absorption of the terrestrial H. SIHLA takes an existing scanning imaging spectrograph (SIS) and adds a Hydrogen Absorption Cell (HAC). The SIS produces spectral images from 115nm to 180 nm - including the H Lyman a line (at 121.6nm)- at all points in the sky. SIHLA uses the HAC, and our observing geometry, to sample, over time, the entire H Lyman a lineshape. The line-of-sight integrated lineshape contains, within it, information on the density, temperature and velocity of Heliospheric H. Remote sensing measurements from SIHLA, and the contributions of our international team, ensure the continuation of the legacy of the SOHO/SWAN mission into the next solar cycle. SIHLA's enhanced capabilities will provide new insights into the Heliospheric boundary and the processes that shape the distribution of H within the heliosphere. These new and unique observations from SIHLA, together with observations from IMAP and Voyager 2, will lead to a revolution in our understanding of the ISM-Heliosphere interaction.

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Publishing type：Research paper (scientific journal)   Publisher：Japan Society for Aeronautical and Space Sciences  

DOI： 10.2322/tastj.17.51

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

Thermal Infrared Imager TIR on Hayabusa2 has proven its in-flight performance to detect celestial bodies during the cruise phase, especially by the observations of the Earth and the Moon before and after the Earth swing-by on 3rd of December 2015. The result indicates that the target C-type asteroid 162173 Ryugu will be detected from the distance of 3000 km at the beginning of the approach phase, and that a C-type small moon larger than 1 m will be detected from the home position, 20 km from the asteroid, if it orbits around the asteroid.

DOI： 10.1016/j.pss.2018.05.007

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Institute of Physics Inc.  

Newly designed Lyman-alpha absorption cells for imaging hydrogen planetary corona were characterized using an ultra high resolution Fourier transform spectrometer installed on the DESIRS (Dichroïsme Et Spectroscopie par Interaction avec le Rayonnement Synchrotron) beamline of Synchrotron SOLEIL in France. The early absorption cell installed in the Japanese Mars orbiter NOZOMI launched in 1998 had not been sufficiently optimized due to its short development time. The new absorption cells are equipped with the ability to change various parameters, such as filament shape, applied power, H2 gas pressure, and geometrical configuration. We found that the optical thickness of the new absorption cell was ∼4 times higher than the earlier one at the center wavelength of Lyman-alpha absorption, by optimizing the condition to promote thermal dissociation of H2 molecules into two H atoms on a hot tungsten filament. The Doppler temperature of planetary coronas could be determined with an accuracy better than 100 K with the performance of the newly developed absorption cell.

DOI： 10.1063/1.5007812

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DOI： 10.1186/s40623-018-0789-5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Blackwell Publishing Ltd  

The existence of large stationary gravity waves was discovered during Akatsuki's first observation sequence in 2015. In this study, the further detection of large stationary gravity waves in brightness temperature images over a 1.5 year period is reported. The waves periodically appeared mostly above four specific highland regions in the low latitudes when these regions were in the local afternoon. The wave amplitudes attenuated after the wave locations passed beyond the evening terminator, and the locations of the waves tended to slowly drift eastward over their lifetimes. The appearances of stationary waves depend not only on surface topography but also on latitude and local time, suggesting that solar heating during the daytime and atmospheric structure affected by solar heating may control the excitation and propagation of stationary waves.

DOI： 10.1002/2017GL075792

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

© 2017, The Author(s). We provide an overview of data products from observations by the Japanese Venus Climate Orbiter, Akatsuki, and describe the definition and content of each data-processing level. Levels 1 and 2 consist of non-calibrated and calibrated radiance (or brightness temperature), respectively, as well as geometry information (e.g., illumination angles). Level 3 data are global-grid data in the regular longitude–latitude coordinate system, produced from the contents of Level 2. Non-negligible errors in navigational data and instrumental alignment can result in serious errors in the geometry calculations. Such errors cause mismapping of the data and lead to inconsistencies between radiances and illumination angles, along with errors in cloud-motion vectors. Thus, we carefully correct the boresight pointing of each camera by fitting an ellipse to the observed Venusian limb to provide improved longitude–latitude maps for Level 3 products, if possible. The accuracy of the pointing correction is also estimated statistically by simulating observed limb distributions. The results show that our algorithm successfully corrects instrumental pointing and will enable a variety of studies on the Venusian atmosphere using Akatsuki data.

DOI： 10.1186/s40623-017-0749-5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

The hydrogen exosphere constitutes the uppermost atmospheric layer of the Earth, and its shape may reflect the last stage of the atmospheric escape process. The distribution of hydrogen in the outer exosphere remains unobserved because outer geocoronal emissions are difficult to observe from within the exosphere. In this study, we used the Lyman Alpha Imaging Camera on board the Proximate Object Close Flyby with Optical Navigation spacecraft, located outside the exosphere, to obtain the first image of the entire geocorona that extends to more than 38 Earth radii. The observed emission intensity distribution can be reproduced using our analytical model that has three parameters: exobase temperature, exobase density, and solar radiation pressure, which implies that hot hydrogen production in the magnetized plasmasphere is not the dominant process shaping the outer hydrogen exosphere. However, the role of the magnetic effect in determining the total escape flux cannot be ruled out.

DOI： 10.1002/2017GL075915

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

The Venus Climate Orbiter Akatsuki arrived at Venus in December 2015, and the Longwave Infrared Camera (LIR) onboard the spacecraft started making observations. LIR has acquired more than 8000 images during the first two Venusian years since orbit insertion without any serious faults. However, brightness temperature derived from LIR images contained an unexpected bias that related not to natural phenomena but to a thermal condition of the instrument. The bias could be partially eliminated by keeping the power supply unit for LIR always active, while the residual bias was simply correlated with the baffle temperature. Therefore, deep-space images were acquired at different baffle temperatures on orbit, and a reference table for eliminating the bias from images was prepared. In the corrected images, the brightness temperature was similar to 230 K at the center of the Venus disk, where the effect of limb darkening is negligible. The result is independent of the baffle temperature and consistent with the results of previous studies. Later, a laboratory experiment with the proto model of LIR showed that when the germanium (Ge) lens was heated, its actual temperature was slightly higher than the temperature measured by a thermal sensor attached to the lens holder. The experiment confirmed that transitory baffle heating accounted for the background bias found in the brightness temperature observed by LIR.

DOI： 10.1186/s40623-017-0727-y

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Language：English  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

The water production rate of a comet is one of the. fundamental parameters necessary. to understand cometary activity when a comet approaches the Sun within 2.5 au, because water is the most abundant icy material in the cometary nucleus. Wide-field imaging observations of the hydrogen Ly alpha emission in comet 67P/Churyumov-Gerasimenko were performed by the Lyman Alpha Imaging Camera (LAICA) on. board the 50 kg class micro spacecraft, the Proximate Object Close Flyby with Optical Navigation (PROCYON), on UT 2015 September 7.40, 12.37, and 13.17 (corresponding to 25.31, 30.28, and 31.08 days after the perihelion passage of the comet, respectively). We derive the water production rates, QH(2)O, of the comet from Lya images of the comet by using a 2D axi-symmetric Direct Simulation Monte-Carlo model of the atomic hydrogen coma; (1.46. +/- 0.47) x 10(28), (1.24. +/- 0.40) x10(28), and (1.30. +/- 0.42) x 10(28) molecules s(-1) on 7.40, 12.37, and 13.17 September, respectively. These values are comparable to the values from in situ measurements by the Rosetta instruments in the 2015 apparition and the ground-based and space observations during the past apparitions. The comet did not show significant secular change in average water production rates just after the perihelion passage for the apparitions from 1982 to 2015. We emphasize that the measurements of absolute QH(2)O based on the wide field of view (e. g., by the LAICA/PROCYON) are so important to judge the soundness of the coma models used to infer QH(2)O based on in situ measurements by spacecraft, like the Rosetta.

DOI： 10.3847/1538-3881/153/2/76

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

The planet Venus is covered by thick clouds of sulfuric acid that move westwards because the entire upper atmosphere rotates much faster than the planet itself. At the cloud tops, about 65 km in altitude, small-scale features are predominantly carried by the background wind at speeds of approximately 100 ms(-1). In contrast, planetary-scale atmospheric features have been observed to move slightly faster or slower than the background wind, a phenomenon that has been interpreted to reflect the propagation of planetary-scale waves. Here we report the detection of an interhemispheric bow-shaped structure stretching 10,000 km across at the cloud-top level of Venus in middle infrared and ultraviolet images from the Japanese orbiter Akatsuki. Over several days of observation, the bow-shaped structure remained relatively fixed in position above the highland on the slowly rotating surface, despite the background atmospheric super rotation. We suggest that the bow-shaped structure is the result of an atmospheric gravity wave generated in the lower atmosphere by mountain topography that then propagated upwards. Numerical simulations provide preliminary support for this interpretation, but the formation and propagation of a mountain gravity wave remain difficult to reconcile with assumed near-surface conditions on Venus. We suggest that winds in the deep atmosphere may be spatially or temporally more variable than previously thought.

DOI： 10.1038/NGEO2873

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DOI： 10.1007/s11214-016-0286-8

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

A new Mid-Infrared Laser Heterodyne Instrument (MILAHI) with &gt; 10(6) resolving power at 7-12 mu m was developed for continuous monitoring of planetary atmospheres by using dedicated ground-based telescopes for planetary science at Mt. Haleakala, Hawaii. Room-temperature-type quantum cascade lasers (QCLs) that cover wavelength ranges of 7.69-7.73, 9.54-9.59, and 10.28-10.33 mu m have been newly installed as local oscillators to allow observation of CO2, CH4, H2O2, H2O, and HDO. Modeling and predictions by radiative transfer code gave the following scientific capabilities and measurement sensitivities of the MILAHI. (1) Temperature profiles are achieved at altitudes of 65-90 km on Venus, and the ground surface to 30 km on Mars. (2) New wind profiles are provided at altitudes of 75-90 km on Venus, and 5-25 km on Mars. (3) Direct measurements of the mesospheric wind and temperature are obtained from the Doppler-shifted emission line at altitudes of 110 km on Venus and 75 km on Mars. (4) Detections of trace gases and isotopic ratios are performed without any ambiguity of the reproducing the terrestrial atmospheric absorptions in the observed wavelength range. A HDO measurement of twice the Vienna Standard Mean Ocean Water (VSMOW) can be obtained by 15-min integration, while H2O of 75 ppm is provided by 3.62-h integration. The detectability of the 100 ppb-CH4 on Mars corresponds to an integration time of 32 h. (C) 2016 Elsevier Ltd All rights reserved.

DOI： 10.1016/j.pss.2016.04.002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

AKATSUKI is the Japanese Venus Climate Orbiter that was designed to investigate the climate system of Venus. The orbiter was launched on May 21, 2010, and it reached Venus on December 7, 2010. Thrust was applied by the orbital maneuver engine in an attempt to put AKATSUKI into a westward equatorial orbit around Venus with a 30-h orbital period. However, this operation failed because of a malfunction in the propulsion system. After this failure, the spacecraft orbited the Sun for 5 years. On December 7, 2015, AKATSUKI once again approached Venus and the Venus orbit insertion was successful, whereby a westward equatorial orbit with apoapsis of similar to 440,000 km and orbital period of 14 days was initiated. Now that AKATSUKI's long journey to Venus has ended, it will provide scientific data on the Venusian climate system for two or more years. For the purpose of both decreasing the apoapsis altitude and avoiding a long eclipse during the orbit, a trim maneuver was performed at the first periapsis. The apoapsis altitude is now similar to 360,000 km with a periapsis altitude of 1000-8000 km, and the period is 10 days and 12 h. In this paper, we describe the details of the Venus orbit insertion-revenge 1 (VOI-R1) and the new orbit, the expected scientific information to be obtained at this orbit, and the Venus images captured by the onboard 1-mu m infrared camera, ultraviolet imager, and long-wave infrared camera 2 h after the successful initiation of the VOI-R1.

DOI： 10.1186/s40623-016-0457-6

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Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved. Japan&#039;s Venus Climate Orbiter Akatsuki was proposed to ISAS (Institute of Space and Astronautical Science) in 2001 as an interplanetary mission. We made 5 cameras with narrow-band filters to image Venus at different wavelengths to track the cloud and minor components distribution at different heights to study the Venusian atmospheric dynamics in 3 dimension. It was launched on May 21st, 2010 and reached Venus on December 7th, 2010. With the thrust by the orbital maneuver engine, Akatsuki tried to go into the westward equatorial orbit around Venus with the 30 hours&#039; orbital period, however it failed by the malfunction of the propulsion system. Later the spacecraft has been orbiting the sun for 5 years. On December 7th, 2015 Akatsuki met Venus again after the orbit control and Akatsuki was put into the westward equatorial orbit whose apoapsis is about 0.44 million km and orbital period of 14 days. Its main target is to shed light on the mechanism of the fast atmospheric circulation of Venus. The systematic imaging sequence by Akatsuki is advantageous for detecting meteorological phenomena with various temporal and spatial scales. We have five photometric sensors as mission instruments for imaging, which are 1 m-infrared camera (IR1), 2 m-infrared camera (IR2), ultra-violet imager (UVI), long-wave infrared camera (LIR), and lightning and airglow camera (LAC). These photometers except LIR have changeable filters in the optics to image in certain wavelengths. Akatsuki&#039;s long elliptical orbit around Venus is suitable for obtaining cloud-tracked wind vectors over a wide area continuously from high altitudes. With the observation, the characterizations of the meridional circulation, mid-latitude jets, and various wave activities are anticipated. The technical issues of Venus orbit insertion in 2015 and the scientific new results will be given in this paper.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

Color images of six low-latitude auroral events observed using color digital cameras at Nayoro (142.5 degrees E, 44.4 degrees N), Hokkaido, Japan, from 2001 to 2004, were analyzed to determine the events' locations and times of occurrence. Geographical azimuthal and elevation angles of the images' pixels were determined precisely by using the positions of the stars captured in the images. Horizontal regions covered by these auroral events were directly indicated by mapping the color images onto geographical maps and assuming that the emission layer's altitude is the lowest or highest value of a visible-level red aurora, as determined by the OI 630.0nm emission. The estimated geomagnetic latitudes and L values of these low-latitude auroral events were in the 39-50 degrees range and below L < 2.5, respectively. This investigation indicates that four of the six auroral events were the same as those that were reported previously based on high-sensitivity optical observations at other sites on Hokkaido (Rikubetsu and Moshiri). Although the previous study is lacking information about the maximal brightness level of the red auroral events, the present investigation suggests that these four low-latitude auroral events reached the visible level. In addition, two new events were reported in this study. The present work provides essential information such as the morphology and appearance of visible auroras, which are extremely rare in mid- or low-latitude regions.

DOI： 10.1186/s40623-015-0278-z

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Publishing type：Research paper (international conference proceedings)  

This study objectives are to devise orbit design methods and propose orbits fulfilling orbit constraints. The orbits were designed as follows: The orbiter's longitude of ascending node and argument of periapsis, in a Mars-Sun fixed coordinate system, are taken as design variables and the orbit constraint, proposed by a science group, is used as an evaluation function. A curved line that expresses a change history of orbiter's elements is draw in the plane. As a result, it is possible to find out rough initial values of longitude of ascending node and argument of periapsis suitable for the mission visually by moving the curved line, and also rough values of periapsis altitude, apoapsis altitude and inclination by choosing a form of orbit profile matching to the evaluation function.

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Language：English   Publisher：EDP SCIENCES S A  

DOI： 10.1051/0004-6361/20079241e

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Language：Japanese   Publishing type：Research paper (other academic)  

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Language：Japanese   Publishing type：Research paper (other academic)  

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Language：English   Publishing type：Research paper (scientific journal)  

Japanese Venus Climate Orbiter/AKATSUKI was proposed in 2001 with strong support by international Venus science community and approved as an ISAS (The Institute of Space and Astronautical Science) mission soon after the proposal. The mission life we expected was more than two Earth years in Venus orbit. AKATSUKI was successfully launched at 06:58:22JST on May 21, 2010, by H-IIA F17. After the separation from H-IIA, the telemetry from AKATSUKI was normally detected by DSN Goldstone station (10:00JST) and the solar cell paddles' deployment was confirmed. After a successful cruise, the malfunction happened on the propulsion system during the Venus orbit insertion (VOI) on Dec. 7, 2010. The engine shut down before the planned reduction in speed to achieve. The spacecraft did not enter the Venus orbit but entered an orbit around the Sun with a period of 203 days. Most of the fuel still had remained, but the orbital maneuvering engine was found to be broken and unusable. However, we have found an alternate way of achieving orbit by using only the reaction control system (RSC). We had adopted the alternate way for orbital maneuver and three minor maneuvers in Nov. 2011 were successfully done so that AKATSUKI would meet Venus in 2015. We are considering several scenarios for VOI using only RCS. © 2013 IAA.

DOI： 10.1016/j.actaastro.2013.07.027

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

A fireball meteor with a visual magnitude over -6 followed by a persistent train was observed by two all-sky cameras for detecting the aurora and sodium airglow at Syowa Station (69.0 degrees S, 39.5 degrees E), Antarctica, on 7 June 2008. The orbit and other parameters of the fireball were estimated with an all-sky television camera for detecting the aurora. After the passage of this fireball, a circular train in the Na airglow was observed. This train expanded to a diameter of about 50 km in 9 min. Assuming that the fireball contained and emitted Na, we found this ring to span the altitudes of z = 76 to 87 km. The ring's mean motion was most likely caused by a large-scale, inertia-gravity wave with a vertical wavelength of similar to 16 km and an amplitude of similar to 30 m/s in the mesopause region.

DOI： 10.1002/jgrd.50228

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Language：English   Publishing type：Research paper (scientific journal)  

The Telescope of Extreme Ultraviolet (TEX) onboard Japan's lunar orbiter KAGUYA provided the first sequential images of the Earth's plasmasphere from the "side" (meridian) view. The TEX instrument obtained the global distribution of the terrestrial helium ions (He+) by detecting resonantly scattered emission at 30.4 nm. One of the most striking features of the plasmasphere found by TEX is an arc-shaped structure of enhanced brightness, which we call a "plasmaspheric filament". In the TEX image on 2 June 2008, the filament structure was clearly aligned to the dipole magnetic field line of L = 3.7 at 7.3 magnetic local time. Our analysis suggests that the filament represents an isolated flux tube filled with four times higher He + density than its neighbors. We found four events of plasmaspheric filament in the images obtained between March and June 2008, and in all four events, the geomagnetic activity was quite low. The plasmaspheric filament in the TEX image is the first evidence that a "finger" structure seen in the IMAGE-EUV image is the projection of an isolated flux tube. © 2013. American Geophysical Union. All Rights Reserved.

DOI： 10.1002/grl.50124

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Language：Japanese   Publishing type：Research paper (other academic)  

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Language：Japanese   Publishing type：Research paper (other academic)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：UNIVELT INC  

The balloon-borne telescope is a planetary observation method launching a telescope to the altitude of more than 30 km by a stratospheric balloon. To conduct the long duration observation, the flight gondola has to equip with a pointing control system in order to catch and keep the target star in the field of view of the telescope during the flight. This research aims to develop the high accuracy pointing control system and conduct the technology demonstration flight. The goal of the pointing control is set as 0.1 arcsec. This paper introduces the results of the ground test and simulation study to evaluate the performance of the pointing control system.

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

CiNii Article

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

Poleward-moving auroral forms (PMAF), the ionospheric signatures of flux transfer events (FTEs), are intermittent phenomena observed in the cusp during negative interplanetary magnetic field intervals. Previous meridian scanning photometer-based observations showed that the distribution of the separation time between successive PMAFs is maximum at similar to 3.5 min. In this paper we present initial results from a new high-sensitivity all-sky imager, which was set up at Longyearbyen, Svalbard, Norway in October 2011. The 630.0-nm all-sky images taken with a time resolution of 4 s reveal that one of the PMAFs that occurred with such typical separation times on 29 December 2011 comprises two consecutive auroral bursts-the first occurring in the PMAF immediately after it was seen and the second, similar to 2 min later, following almost the same route. This observation provides evidence that one PMAF could reflect double FTEs-there is not always a one-to-one correspondence between FTEs and PMAFs. Reconnection on the dayside magnetopause would be modulated with a period of similar to 2 min during the course of transient reconnection. Citation: Taguchi, S., K. Hosokawa, Y. Ogawa, T. Aoki, and M. Taguchi (2012), Double bursts inside a poleward-moving auroral form in the cusp, J. Geophys. Res., 117, A12301, doi:10.1029/2012JA018150.

DOI： 10.1029/2012JA018150

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE  

Mid-infrared images of almost the entire Venus nightside hemisphere obtained by the Longwave Infrared Camera (LIR) onboard Akatsuki on December 9 and 10, 2010 reveal that the brightness temperature of the cloud-top ranges from 237 K in the cold polar collars to 243 K in the equatorial region, significantly higher than the values obtained by Venera 15. Other characteristic features of the temperature distributions observed are zonal belt structures seen in the middle and low latitudes and patchy temperature structures or quasi-periodic streaks extending in a north-south direction in the northern middle latitudes and southern low latitudes. (c) 2012 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.icarus.2012.01.024

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Publishing type：Research paper (international conference proceedings)  

Japanese Venus Climate Orbiter/AKATSUKI was proposed in 2001 with strong support by international Venus science community and approved as an ISAS (Institute of Space and Astronautical Science) mission soon after the proposal. The mission life we expected was more than two Earth years in Venus orbit. AKATSUKI was successfully launched at 06:58:22JST on May 21, 2010, by H-IIA F17. After the separation from H-IIA, the telemetry from AKATSUKI was normally detected by DSN Goldstone station (10:00JST) and the solar cell paddles' expansion was confirmed. The malfunction happened on the propulsion system during the Venus orbit insertion (VOI) on Dec 7, 2010. We failed to make the spacecraft become a Venus orbiter, and the spacecraft entered an orbit around the Sun with a period of 203 days. Most of the fuel still had remained, but the orbital maneuvering engine was found to be broken. We decided to use only the reaction control system (RCS) for orbital maneuver and three minor maneuvers in Nov 2011 were successfully done so that AKATSUKI will meet Venus in 2015. We are considering several scenarios for VOI using only RCS. Copyright © (2012) by the International Astronautical Federation.

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J-GLOBAL

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DOI： 10.1109/SII.2012.6427318

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Aerospace Exploration Agency  

Variations of electron density in the ionosphere accompanied by traveling ionospheric disturbances and plasma bubbles have been observed using ground-based airglow imaging and total electron content (TEC) measurements by a GPS network. However, these ground-based observations can detect only a portion of such wide-area phenomena, because the field-ofview from a ground station is limited. On the other hand, the intensity of the OI 135.6 nm night airglow emitted by radiative recombination processes is proportional to the square of the electron density in the F-region. Imaging the OI 135.6 nm emission using a geostationary satellite can reveal the entire distribution of these ionospheric phenomena. To detect variations in the weak OI 135.6 nm emission (~10 R) in middle and high latitudes with a spatial resolution of 100 km and a signal count of 1000 for an exposure time of 20 min, a sensitivity of 0.075 cts/s/R/pixel is required for a satellite-borne far ultraviolet (FUV) imager. For this reason, we adopted fast Schmidt optics for the FUV imager. The most technically challenging aspect of the design of such optics is the fabrication of an aspheric corrector using a vacuum ultraviolet transparent crystalline material such as MgF_2. In the present study, two different machining processes, magneto-rheological finishing and highaccuracy grinding, were compared for fine finishing the aspheric surfaces of the MgF_2 plates. The quality of the finished surfaces was evaluated by optical interferometry, and it was confirmed that a surface accuracy of 0.5λ PV (peak-to-valley) @ 135.6 nm was achieved with both processes. Since high-accuracy grinding was found to be more appropriate with regard to machining time, an aspheric surface with a 60% diameter (= 60 mm) and a maximum gradient and sag identical to those for the flight model corrector was manufactured using this process. The accuracy of the finished surface was evaluated to be 0.53λ PV. Simulations were then carried out to determine the overall optical performance of a corrector fabricated in this manner, and it was concluded that Schmidt optics using such a corrector can achieve the spatial resolution required for the FUV imager

CiNii Article

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

In this study, we determined the characteristics of mesospheric wave structures over South Pole Station (90 degrees S) derived from sodium airglow imaging observations. During the winter months of 2003 to 2005 (105 nights), we extracted a total of 768 wave events and separated them into two types (band-type gravity waves and ripples) according to their horizontal wavelengths. The distributions of the observed wave parameters, except for the horizontal propagation directions, were similar to those obtained by imaging observations at other latitudes. The observed gravity waves showed a preference for propagation toward 30-60 degrees E and 210-240 degrees E, whereas the ripples showed a preference for motion toward 90-120 degrees E and 300-330 degrees E. The gravity waves had a weak tendency of being observed in 0100-0700 UT, although the ripples did not show such a time dependence. We also investigated the characteristics of atmospheric instabilities from the alignment of the phase fronts of the observed ripples.

DOI： 10.1029/2011JD015882

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Language：Japanese   Publishing type：Research paper (other academic)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

We have succeeded in imaging of the terrestrial plasmasphere by the Telescope of Extreme Ultraviolet (TEX) aboard Japan's lunar orbiter KAGUYA. The view afforded by the KAGUYA orbit encompasses the plasma distribution in a single exposure, enabling us to examine for the first time the globally-averaged properties of the plasmasphere from the "side" (meridian) perspective. This is the world first image of the plasmasphere from the moon.

DOI： 10.2322/tastj.8.Tn_23

CiNii Article

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

The Longwave Infrared Camera (LIR) is one of a suite of cameras onboard the Venus orbiter Akatsuki. It will take images of thermal radiation in the wavelength range of 8-12 mu m emitted by the Venus cloud tops. The use of an uncooled micro-bolometer array as an infrared image sensor makes LIR a lightweight, small and low-power consumption instrument with a required noise equivalent temperature difference of 0.3 K. Temperature and horizontal wind fields at the cloud-top will be retrieved for both dayside and nightside with equal quality. This will provide key observations to understand the mechanism of super rotation and the thermal budget of the planet. LIR will also monitor variations of the polar dipole and collar which are characteristic thermal features in the Venusian atmosphere. Mechanisms of the upper-cloud formation will be investigated using sequences of close-up images. The morphology of the nightside upper cloud will be studied in detail for the first time.

DOI： 10.5047/eps.2011.06.019

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

The Akatsuki spacecraft of Japan was launched on May 21, 2010. The spacecraft planned to enter a Venus-encircling near-equatorial orbit in December 7, 2010; however, the Venus orbit insertion maneuver has failed, and at present the spacecraft is orbiting the Sun. There is a possibility of conducting an orbit insertion maneuver again several years later. The main goal of the mission is to understand the Venusian atmospheric dynamics and cloud physics, with the explorations of the ground surface and the interplanetary dust also being the themes. The angular motion of the spacecraft is roughly synchronized with the zonal flow near the cloud base for roughly 20 hours centered at the apoapsis. Seen from this portion of the orbit, cloud features below the spacecraft continue to be observed over 20 hours, and thus the precise determination of atmospheric motions is possible. The onboard science instruments sense multiple height levels of the atmosphere to model the three-dimensional structure and dynamics. The lower clouds, the lower atmosphere and the surface are imaged by utilizing near-infrared windows. The cloud top structure is mapped by using scattered ultraviolet radiation and thermal infrared radiation. Lightning discharge is searched for by high speed sampling of lightning flashes. Night airglow is observed at visible wavelengths. Radio occultation complements the imaging observations principally by determining the vertical temperature structure.

DOI： 10.5047/eps.2011.02.009

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Resonant scattering of the lunar sodium exosphere was measured from the lunar orbiter SELENE (Kaguya) from December 2008 to June 2009. Variations in line-of-sight integrated intensity measured on the night-side hemisphere of the Moon could be described as a spherical symmetric distribution of the sodium exosphere with a temperature of 2400-6000 K. Average surface density of sodium atoms in February is well above that in the other months by about 30%. A clear variation in surface density related to the Moon&apos;s passage across the Earth&apos;s magnetotail could not be seen, although sodium density gradually decreased (by 20 +/- 8%) during periods from the first through the last quarter of two lunar cycles. These results suggest that the supra-thermal components of the sodium exosphere are not mainly produced by classical sputtering of solar wind. The variation in sodium density (which depends on lunar-phase angle) is possibly explained by the presence of an inhomogeneous source distribution of photon-stimulated desorption (PSD) on the surface. (c) 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.pss.2010.07.025

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

The Telescope of Extreme Ultraviolet (TEX) aboard Japan's lunar orbiter Kaguya has succeeded in imaging of the plasmaspheric helium ions by detecting resonantly scattered emission at 30.4 nm. After the initial instrumental check was completed, TEX has been operated routinely, and EUV images from TEX have become available from the perspective of the lunar orbit. The view afforded by the Kaguya orbit encompasses the plasma (He+) distribution in a single exposure, enabling us to examine for the first time the globally averaged properties of the terrestrial plasmasphere from the "side" (meridian) perspective. In this paper we report the inward motion of the nightside plasmapause on 2 May 2008 as seen from this remote meridian view of the Earth. The southward turning of the IMF initiated the inward motion of the plasmapause, and the nightside plasmasphere shrunk at a rate of 0.2 Re/h. Simultaneous solar wind velocity measurements provide a possible explanation for the total radial displacement of the plasmasphere observed in the EUV images.

DOI： 10.1029/2009JA014978

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DOI： 10.2322/tstj.7.Tk_27

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DOI： 10.1142/9789812838162_0009

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Language：Japanese   Publishing type：Research paper (other academic)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

Our team is carrying out the project of Planet observation with high precision using balloon-borne telescope. The first model, BBT-1 was equipped with a three stage pointing system and an optical system to observe the detailed structure of the atmospheric motion of Venus. The first flight test was conducted in 2009, and the performance of the system was verified. However, because of a trouble of onboard computer, the flight operation could not been finished as planned. The second model "BBT-2" is now being developed and the next flight test is planned in 2011.The BBT-2 has a bus system including FPGAs and CPU,and it is expected to be more stable than the BBT-1. ©2010 IEEE.

DOI： 10.1109/SII.2010.5708331

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

A balloon borne telescope is one of the space observation methods by carrying a telescope to the stratosphere with a huge balloon in order to be free from the atmospheric influences on observations. The authors have been developing a balloon borne telescope system for optical observations of other planets in the solar system. The observation aimed to achieve finer images of the planets than those taken by ground telescopes, which required the balloon borne telescope to hold the target star with subarcsec precision during the exposure of the camera. To meet the requirement, the system is equipped three stage pointing system. This article introduces the overview of the flight campaign and the flight system, and reports the pointing performance verified in ground experiments.

DOI： 10.2322/tastj.8.Pm_15

CiNii Article

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

A grating spectrometer for hydroxyl (OH) airglow installed at Syowa Station (69 degrees S, 39.6 degrees E) by the 49th Japanese Antarctic Research Expedition (JARE49) has been in operation since late February, 2008. A dataset of 153 nights was acquired at this location in the austral winter season of 2008. This dataset shows variations in the rotational temperature over a range of temporal scales. The rotational temperature around the polar mesopause region is high in winter and decreases toward summer, which is a pattern similar to that observed at Davis Station, located at almost the same latitude as Syowa Station. A large temperature variation with a period of several days was observed in early May, 2008. Based on a comparison with a simultaneous dataset obtained by the SABER instrument onboard the TIMED satellite, it is inferred that this rotational temperature variation was due to the modulation of vertical motions around the mesopause.

DOI： 10.5047/eps.2010.07.010

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TERRA SCIENTIFIC PUBL CO  

Our understanding of plasmaspheric dynamics has increased in recent years largely due to the information generated during the IMAGE-EUV mission. Even though this successful mission has ended, we have succeeded in imaging the terrestrial helium ions (He(+)) by the Telescope of Extreme Ultraviolet (TEX) aboard the Japanese lunar orbiter KAGUYA by detecting resonantly scattered emission at 30.4 nm. The view afforded by the KAGUYA orbit encompasses the plasma (He(+)) distribution in a single exposure, enabling us to examine for the first time the globally averaged properties of the plasmasphere from the "side" (meridian) perspective. The TEX instrument observed a medium-scale density structure in the dawnside plasmasphere during a quiet period (1-2 June 2008). The meridian shape of the structure clearly agreed with the dipole magnetic field line. The TEX instrument also observed the structure in the plasmasphere co-rotating with a duration of 26 h, which is consistent with results from a number of recent studies derived from the IMAGE-EUV mission. These results confirm that the TEX instrument successfully obtained the spatial distribution and temporal variation of the plasmasphere.

DOI： 10.5047/eps.2010.02.006

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：COPERNICUS GESELLSCHAFT MBH  

OH rotational temperatures have been observed at the Syowa Station, Antarctica (69 degrees S, 39 degrees E), which is located in the middle of the auroral zone and has a high-sensitivity spectrometer for the spectral region of the OH 8-4 band. A dataset of 153 nights was acquired during the 2008 austral winter season. Of the 153 nights, the weather and aurora conditions were only suitable on 6 nights to study the relationship between auroral activity and OH airglow variation. Of these 6 nights, a significant increase in the rotational temperature and a decrease in the intensity related to an aurora activity were identified on the night of 27/28 March 2008, but no such variations were seen during the other nights. The horizontal magnetic field disturbance on the night of 27/28 March was the largest of that winter, while the cosmic radio noise absorption was also very strong. These facts indicate that, compared with the other nights, a large flux of high-energy auroral particles precipitated during the night. It is suggested that the observed variations in the OH rotational temperature and airglow intensity were caused by a lowering of the average airglow height as a result of OH depletion in the upper part of the layer where high-energy auroral particles can reach.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We measured the 220 GHz atmospheric-transparency at the Dome Fuji station in Antarctica from 18 December 2006 to 14 January 2007 using a tipping radiometer. The mean optical depth at zenith was 0.045 +/- 0.007, and during 98% of this period we measured an optical depth of less than 0.06. These data indicate that the atmospheric-transparency in summer at Dome Fuji is comparable to that of well-known submillimeter astronomical sites such as the Atacama desert in Chile in their best seasons. (C) 2009 Elsevier B.V. and NIPR. All rights reserved.

DOI： 10.1016/j.polar.2009.08.001

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Observations acquired from three-wavelength (427.8, 557.7 and 630.0 nm) all-sky imagers (ASIs) at Yellow River Station (YRS) in Ny-Alesund, Svalbard, are used to examine the synoptic distribution of dayside aurora. The results demonstrate that the maximum emission regions (MERs) at each wavelength are all located in the postnoon sector, but have rather different magnetic local time (MLT) distributions from each other. The so-called 15 MLT "hot spot" is the overlapping region of the MERs at three wavelengths, and the prenoon "warm spot" is characterized uniquely by an increase of emissions at the 557.7 nm wavelength. The detailed dayside auroral spectra and morphology as a function of MLT are discussed. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jastp.2009.02.010

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (other academic)  

筆頭

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

The interplanetary Lyman a backscattered emission is an effective tool for remote sensing of the global structure of the solar wind proton flux. This paper reports an attempt to derive the latitudinal dependence of the solar wind density by combining the interplanetary Lyman alpha measurements of the Nozomi spacecraft for the period 1999-2002 with the solar wind speed data derived from interplanetary scintillation measurements, This approach successfully revealed the slow and dense solar wind over the poles during the period of the solar maximum. Data on the. polar solar wind density indicate a significant gyowth from the middle of 2000, and the polar values of solar wind density are close to those of the equatorial values as a result of the disappearance of the coronal hole. A marked density depletion occurred in the middle of 200 1, which can be ascribed to the development of fast winds from the polar coronal hole. To evaluate the remote sensing method, we considered solar wind density data from in Situ measurements obtained by the Ulysses spacecraft. We conclude that our method basically agrees with in situ measurements, although we found a significant (a factor of 2) difference between these in the middle of 2001.

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Language：English   Publishing type：Research paper (scientific journal)  

CiNii Article

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TERRA SCIENTIFIC PUBL CO  

The first successful observations of resonant scattering emission from the lunar sodium exosphere were made from the lunar orbiter SELENE (Kaguya) using TVIS instruments during the period 17-19 December, 2008. The emission intensity of the NaD-line decreased by 12 +/- 6%, with an average value of 5.4 kR (kilorayleighs) in this period, which was preceded, by I day, by enhancement of the solar proton flux associated with a corotating interaction region. The results suggest that solar wind particles foster the diffusion of sodium atoms or ions in the lunar regolith up to the surface and that the time scale of the diffusion is a few tens of hours. The declining activity of the Geminid meteor shower is also one possible explanation for the decreasing sodium exosphere.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：TERRA SCIENTIFIC PUBL CO  

The Upper Atmosphere and Plasma Imager (UPI) was placed in a lunar orbit in order to Study both the Moon and Earth. The UPI consists of two telescopes: a Telescope of Extreme Ultraviolet (TEX) and a Telescope of Visible Light (TVIS), which are both mounted on a two-axis gimbals system. The TVIS is equipped with fast catadioptric optics and a high-sensitivity CCD to image swift aurora and dark airglow ill the terrestrial upper atmosphere. TVIS has a field-of-view equivalent to the Earth&apos;s disk as seen from the Moon. The spatial resolution is about 30 km x 70 km on the Earth&apos;s surface at auroral latitudes. The observation wavelengths can be changed by selecting different bandpass filters. Using the images of the northern and Southern auroral ovals taken by TVIS, the intensities and shapes of the conjugate auroras will be quantitatively compared. Using the an-low imaging, medium- and large-scale ionospheric disturbances will be Studied. In this paper, the instrumental design and performance of TVIS are presented.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：EDP SCIENCES S A  

Aims. Following recent reports on spectroscopic observations by SWAN/SOHO suggesting that the flows of neutral interstellar helium and hydrogen in the inner heliosphere are slightly divergent, we tried to verify them on the basis of simultaneous photometric observations of heliospheric hydrogen and helium glows performed by a spacecraft located on an orbit between the Earth and Mars (which differs from the orbit of SWAN/SOHO). The observations were interpreted with the use of various independent models of interstellar hydrogen and helium in the inner heliosphere, evaluated over a mesh of parameters.
Methods. The data might suggest that the upwind and downwind directions of interstellar H may differ by less than 180 degrees, which we interpret as due to a side shift of the secondary population of interstellar hydrogen, which might be due to a deformation of the outer heliosheath e.g. because of the action of interstellar magnetic field. The simulations we performed do not support the idea that the secondary population is significantly shifted to the side.
Results. The upwind/downwind direction of interstellar hydrogen as derived from our observations agrees within the error bars with the upwind/downwind direction of interstellar helium and the error bars include both the upwind direction of interstellar helium, derived from in-situ observations of GAS/Ulysses, and the upwind direction of interstellar hydrogen, derived from observations of SWAN/SOHO.

DOI： 10.1051/0004-6361:20079241

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

The Longwave Infrared Camera (LIR), which mounts an uncooled micro-bolometer array (UMBA), is under development for the Japanese Venus orbiter mission, PLANET-C. LIR detects thermal emission from the top of the sulfur dioxide cloud in a wavelength region 8-12 mu m to map the cloud-top temperature which is typically as low as 230 K. The requirement for the noise equivalent temperature difference (NETD) is 0.3 K. Images of blackbody targets in room temperature (similar to 300 K) and low temperature (similar to 230 K) have been acquired in a vacuum environment using a prototype model of LIR, showing that the NETD of 0.2 K and 0.8 K are achieved in similar to 300 K and -230 K, respectively. We expect that the requirement of NETD &lt; 0.3 K for similar to 230 K targets will be achieved by averaging several tens of images which are acquired within a few minutes. The vibration test for the UMBA was also carried out and the result showed the UMBA survived without any pixel defects or malfunctions. The tolerance to high-energy protons was tested and verified using a commercial camera in which a same type of UMBA is mounted. Based on these results, a flight model is now being manufactured with minor modifications from the prototype.

DOI： 10.1117/12.784932

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Language：Japanese   Publishing type：Research paper (other academic)  

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Language：Japanese   Publishing type：Research paper (other academic)  

筆頭

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DOI： 10.1016/j.polar.2007.12.002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TERRA SCIENTIFIC PUBL CO  

The Upper Atmosphere and Plasma Imager (UPI) is to be launched in 2007 and sent to the Moon. From the lunar orbit, two telescopes are to be directed towards the Earth. The Moon has no atmosphere, which results in there being no active emission near the spacecraft; consequently, we will have a high-quality image of the near-Earth environment. As the Moon orbits the Earth once a month, the Earth will also be observed from many different directions. This is called a "science from the Moon". The two telescopes are mounted on a two-axis gimbal system, the Telescope of Extreme ultraviolet (TEX) and Telescope of Visible light (TVIS). TEX detects the O II (83.4 nm) and He II (30.4 nm) emissions scattered by ionized oxygen and helium, respectively. The targets of extreme-ultraviolet (EUV) imaging are the polar ionosphere, the polar wind, and the plasmasphere and inner magnetosphere. The maximum spatial and time resolutions are 0.09 Re and 1 min, respectively.

DOI： 10.1186/BF03352805

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

Tohoku University and Rikkyo University are carrying out the project of Venus observation with high precision using a balloon-borne telescope. In this paper, the outline of Balloon-Borne Telescope for the optical remote sensing of Venus is introduced, and the simulation model of three-stage control method is constructed. For this observation, the pointing technology with high precision to restrain the slight moving of image is necessary. The target precision is only 0.1 arc seconds. The dynamics and control model is defined firstly, and the model parameters are determined by the experimental verification. By developing the numerical simulation tool, the motion can be estimated in the simulator, and the control strategy can be more easily optimized compared to the gain adjustment only based on experiments.

DOI： 10.2322/tstj.7.Pd_23

CiNii Article

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

We present quasi-stationary auroral patches (QSAPs) observed by an all-sky imager at the South Pole Station (-74.3 degrees CGLAT) on the dayside between similar to 0900 and similar to 1400 MLT. QSAPs appeared in a closed field line region where I(557.7 nm) &gt;&gt; I(630.0 nm) and each patch tends to preserve its form, luminosity, and location for up to several hours. The quasi-stationary nature of the QSAPs cannot be explained by the traditional role of the corotation electric field because the South Pole is located on the axis of Earth&apos;s rotation. The most plausible scenario is that a corotation electric potential, which dominates the convection potential, results in a trapping region of the magnetospheric cold plasmas. On the analogy of the formation of the plasmasphere, the trapping region would capture cold plasmas originated from the ionosphere and result in a locally enhanced plasma density (miniplasmasphere) that may lead to electron scattering through cyclotron wave-particle interactions. This circumstance may occur when the South Pole is located on a closed field line and the local electric potential is dominated by the corotation potential. QSAPs were also accompanied with periodic fluctuations in the Pc 5 range, which coincide closely with ground magnetic fluctuations. Assuming that the pulsation is associated with field line resonances, we could estimate the equatorial mass density of thermal plasmas, which gradually increased from 0.13 to 0.44 amu cm(-3). The increase in the thermal plasma density would support the hypothesis that a miniplasmasphere exists, though further investigation is necessary to confirm it.

DOI： 10.1029/2006JA012087

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CiNii Article

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The Longwave Infrared Camera (LIR) onboard the first Japanese Venus mission, PLANET-C, or the Venus Climate Orbiter, operates in the middle infrared region with a single bandpass filter of 8-12 mu m, measuring thermal radiation emitted from the cloud tops of the Venusian atmosphere. A horizontal wind vector field at the cloud-top height will be retrieved by means of a cloud tracking method. In addition, absolute temperature will be determined with an accuracy of 3 K. Since solar irradiation scattered by the atmosphere is much weaker than the atmospheric thermal radiation, LIR can continuously monitor a hemispheric wind field independent of the local time of the apocenter throughout the mission life. Wind and temperature fields obtained by LIR will provide key parameters to solve climatological issues related to the Venusian atmosphere. The use of an uncooled micro-bolometer array (UMBA), which requires no cryogenic apparatus, as an image sensor contributes to the reduction of power consumption and the weight of the LIR imager. An instrumental field-of-view of 12 degrees is equal to the angle subtended by Venus when observed from a height of 9.5 Rv. The pixel field-of-view corresponds to a spatial resolution of 70 km viewed from the apocenter. A mechanical shutter functions not only as an optical shutter but also as a reference blackbody. The temperature stability of the sensor is especially important, because fluctuation of thermal radiation from the internal environment of the sensor itself causes background noise. Therefore, the temperature of the UMBA package is stabilized at 313 +/- 0.1 K with a feedback controlled Peltier cooler/heater, and a NETD of 0.3 K, which is required for this infrared imager, will be achieved. Flat field images are taken with the shutter closed several seconds before and after 1 s exposure for a Venus thermal image. After a Venus image is taken, the LIR imager takes a cold calibration image of deep space. This measurement sequence is repeated every two hours when the spacecraft is orbiting at apocenter. Image data are transmitted down to the Earth after onboard calibration and data compression by common digital electronics. (c) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.asr.2007.05.085

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TERRA SCIENTIFIC PUBL CO  

We have developed three airglow temperature photometers with cooled-CCD detectors. The photometers measure rotational temperatures using the airglow emissions of OH and 02 near the mesopause region (altitude: 80-100 km). The photometers also measure six other airglow and auroral lines at wavelengths of 55.7, 630.0, 777.4, 589.3, 427.8, and 486.1 nm. The CCD detectors are used to distinguish the emission lines in these airglow bands, similarly to those used by the Spectral Airglow Temperature Imagers (SATI). In this paper, we describe the configuration of the photometers, their calibration, the data processing to extract rotational temperatures and emission intensities from the measured airglow spectra, as well as the initial deployment at Platteville, Colorado (40.2 degrees N, 255 degrees E), when their observations were compared with the concurrent and nearly collocated observations by a sodium lidar. We obtain a good correlation and some systematic difference of temperatures from the photometers and the lidar, and discuss possible causes of the temperature difference.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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Other Link： http://orcid.org/0000-0003-1129-334X

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Blackwell Publishing Ltd  

Interplanetary hydrogen atoms that penetrate into the heliosphere are illuminated by enhanced hydrogen Lyman alpha emission from solar active regions. Using the data obtained by the Solar Wind Anisotropies (SWAN) instrument on board the Solar and Heliospheric Observatory (SOHO), Bertaux et al. (2000) proposed a new method for earlier detection and monitoring of solar active regions on the far-side hemisphere. However, a quantitative relationship between the sky map of interplanetary Lyman alpha intensity and the enhanced emission from a solar active region was not discussed. Here, we analyze the interplanetary Lyman alpha intensity data obtained by the Ultraviolet Imaging Spectrometer (UVS) on board the Nozomi spacecraft. We develop a method to map the distribution of interplanetary Lyman alpha intensity into the Carrington coordinate system by assuming an interplanetary hydrogen screen at the location of maximum volume emission rate. Analysis period is from January 2000 to March 2000 near solar maximum. The solar activity during this analysis period is much higher as compared with the case study by Bertaux et al. (2000). The sky map of the Lyman alpha emission obtained by the UVS is shown to exhibit a high correlation with the solar extreme ultraviolet (EUV) intensity map obtained by the EUV Imaging Telescope (EIT) on board the SOHO satellite. The highest value of two-dimensional correlation coefficient is 0.80. An observed change in the periodicity of interplanetary Lyman alpha intensity is in good agreement with the growth of an active region on the Sun. It has been also confirmed that the far-side observations of UVS detected the growth of an active region in advance. This case study demonstrates that the location and intensity variation of activity on the far side of the Sun can be detected by far-side measurements of interplanetary Lyman alpha emission intensity. It is thus concluded that the developed method contributes to space weather forecasting on a scale of 2 weeks. Copyright 2005 by the American Geophysical Union.

DOI： 10.1029/2004JA010828

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Language：English   Publishing type：Research paper (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Blackwell Publishing Ltd  

We have investigated the distributions of neutral interplanetary hydrogen Lyman a emission and their solar cycle dependence from observations with the ultraviolet imaging spectrometer (UVS) onboard the NOZOMI spacecraft and the solar wind anisotropy instrument (SWAN) onboard the solar and heliospheric observatory (SOHO) spacecraft. The SOHO/SWAN observation covers the period from the solar minimum in 1996 to the solar maximum in 2001, while the NOZOMI/UVS observation covers the period of 1999-2001 near the solar maximum. The most distinct feature of the full sky Lyman α intensity maps near the solar maximum in 2000 is a structure with a single bright region extending across the ecliptic plane on the upwind side of the interstellar wind. This structure is entirely different from the structure observed by SWAN at the solar minimum in 1996, which shows an intensity depression called a "groove" and bright lobes above and below the groove centered near the ecliptic plane. From the fitting of model calculations to the observational data, it is confirmed that the latitudinal distribution of the ionization rate of the interplanetary hydrogen due to the charge exchange with solar wind protons becomes isotropic toward the solar maximum. However, an important result is that the condition for producing anisotropic ionization rate due to the slow, high-density solar wind around the equator exists by October 1999, although the theoretical model predicts isotropic ionization rate throughout 1999. Copyright 2003 by the American Geophysical Union.

DOI： 10.1029/2003JA009882

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Language：English   Publishing type：Research paper (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：TERRA SCIENTIFIC PUBL CO  

The geometric albedo of the Moon at the wavelength of hydrogen Lyman alpha (HLy alpha 121.6 nm) was derived from an imaging observation by the ultraviolet imaging spectrometer (UVS) during the lunar encounter of the NOZOMI spacecraft. The solar HLy alpha irradiance data measured by the UARS/SOLSTICE at the time of UVS observation were adopted. We obtained an average geometric albedo of 5.2 +/- 0.9% for the sunlit region where the WS observed. Our result agrees with the geometric albedos obtained from the observations by Apollo 17 and Astro-2/HUT, though the observation geometry and area are completely different from each other. There exists a significant difference of the albedos from place to place in the observed lunar surface ranging from 2.3 +/- 1.1% to 6.0 +/- 1.0%. It is noted that the observed contrast at the FUV wavelength is positive to that seen in the visible region.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：TERRA SCIENTIFIC PUBL CO  

An ultraviolet imaging spectrometer (UVS) on board the PLANET-B (NOZOMI) spacecraft has been developed. The UVS instrument consists of a grating spectrometer (UVS-G), an absorption cell photometer (UVS-P) and an electronics unit (UVS-E). The UVS-G features a flat-field type spectrometer measuring emissions in the FUV and MUV range between 110 nm and 310 nm with a spectral resolution of 2-3 nm. The UVS-P is a photometer separately detecting hydrogen (H) and deuterium (D) Lyman alpha emissions by the absorption cell technique. They take images using the spin and orbital motion of the spacecraft. The major scientific objectives of the UVS experiment at Mars and the characteristics of the UVS are described. The MUV spectra of geocoronal and interplanetary Lyman alpha emissions and lunar images taken at wavelength of hydrogen Lyman alpha and the background at 170 nm are presented as representative examples of the UVS observations during the Earth orbiting phase and the Mars transfer phase.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON PRESS LTD  

This paper reports the development of coordinated observations carried out with the use of the MU radar (middle and upper atmosphere radar) and optical measurement: techniques in Shigaraki. Since the start of the MU radar operation, mesosphere wind and turbulence were studied using mesospheric turbulence echo in the daytime. More recently, meteor echoes have been used to observe wind and temperature around the mesopause, during day and night, Comparative observations with the MU radar meteor mode and sodium lidars were used to study gravity waves and variation of sodium layers. Airglow observations were also carried out as a campaign basis, with which small scale and large scale gravity waves have been studied. We have also developed two CCD imagers to observe airglow images at the MU radar site for long term observations with the radar. Now Skigaraki has become an integrated optical/radar site ready to contribute to the PSMOS (Planetary Scale Mesopause Observing System) project being carried out between 1998-2002, (C) 2000 COSPAR. Published by Elsevier Science Ltd.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON PRESS LTD  

An ultraviolet imaging spectrometer (UVS) has been developed for the PLANET-B spacecraft. The WS instrument is composed of a grating spectrometer (UVS-G) and a D/H absorption cell photometer (UVS-P). The UVS-G is a flat-field type spectrometer measuring optical emissions in the FUV and MUV range between 115 nm and 310 nm with a spectral resolution of 2 - 3 nm. The WS-P is a. photometer detecting hydrogen (H) and deuterium (D) Lyman alpha emissions separately by an absorption cell technique. Scientific targets of the UVS experiment are the investigation of (1) hydrogen and oxygen coronas around Mars, (2) the D/H ratio in the upper atmosphere, (3) dayglow, (4) aurora and nightglow, (5) dust, clouds and ozone, and (6) the surface composition of Phobos and Deimos. (C) 1999 COSPAR. Published by Elsevier Science Ltd.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON PRESS LTD  

An all-sky optical imager is in routine observation at the South Pole. Monochromatic images of aurora and air glow at N-2(+) 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. Super-DARN 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. (C) 1999 COSPAR. Published by Elsevier Science Ltd.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE - INT SOC OPTICAL ENGINEERING  

Using the third version of tunable diode laser heterodyne spectrometers developed by the Tohoku university optical group, infrared absorption spectra of atmospheric O-3, N2O, CH4 and HNO3 were observed at Syowa station (69.0 degrees 8, 39.6 degrees E) from August 1994 to January 1995. This portable spectrometer has an ultra high spectral resolution of 0.0013 cm(-1) and a signal-to-noise ratio of 500 for 10-min scan time. From ozone absorption spectra obtained in early spring, the height profiles of ozone concentration up to 30 km were retrieved at intervals of ten minutes. These profiles showed extremely low ozone concentration in the altitude range of 15-20 km, which is a typical feature of the antarctic ozone hole. Furthermore, these profiles demonstrated the existence of rapid variations of ozone concentration in the altitude range of 20-30 km. From the potential vorticity analysis using the objective analysis data provided by the Japanese meteorological agency, it was concluded that these variations were caused by a passage of westward traveling waves produced at the polar vortex boundary.

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Language：English   Publishing type：Thesis (other)  

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Language：English   Publishing type：Research paper (scientific journal)  

Height distributions of methane in the troposphere and stratosphere were derived from high resolution absorption spectra observed with a ground‐based tunable diode laser heterodyne spectrometer. The center wavenumber of the measured methane absorption line is 1223.1561 cm−1. In the retrieval of methane height profiles, a volume mixing ratio of methane was assumed to have a constant value in the troposphere and to decrease with a constant rate in the stratosphere. The tropospheric mixing ratio and the decreasing rate in stratosphere were derived to be 1.7±0.1 ppmv and −0.06 ppmv/km, respectively, for measurements at Tsukuba (36.0°N, 140.1°E) on December 17 and 20, 1991. © 1995 by the Chinese Geophysical Society

DOI： 10.1029/95GL00051

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

To evaluate the accuracy of the vertical profiles and total column densities obtained by a ground‐based laser heterodyne spectrometer, four ozonesonde measurements were performed at Sendai, Japan in November 28–December 2, 1989. The altitudes, widths and maximum values of the peaks in the ozone vertical distributions obtained by the laser heterodyne observations agreed well with those obtained by the ozonesondes, though the fine structures in the ozone distributions can not be resolved by this remote sensing method. The total column densities and their temporal variation obtained by the laser heterodyne observations were also consistent with the ozonesonde data and the Dobson spectrophotometer data at Sapporo and Tateno. Copyright 1990 by the American Geophysical Union.

DOI： 10.1029/GL017i013p02349

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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, 神奈川県資料番号: SA6000051002レポート番号: I-2

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Language：Japanese   Publisher：The Japanese Society for Planetary Sciences  

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Seeing is the most important condition for high spatial resolution optical imaging by a ground-based telescope. The stable wind and low atmospheric density in the stratosphere provide ideal environment for optical observations of celestial objects. Taking advantages of the stratospheric environment even a small telescope with a sub-meter diameter main mirror can realize high spatial resolution imaging comparable to those by huge ground-based telescopes with a several-meter diameter. The circumpolar balloon-borne telescope, FUJIN, is a telescope floating in the polar stratosphere for optical observations of planets. Since the FUJIN was proposed in 2002, the flight system has been developed. The first flight test was conducted in 2009 to be failed due to hung-up of the onboard CPU. Improvement and further development has been continued, and then the FUJIN-1 flight model was rolled out in 2013. Unfortunately the flight experiment in 2013 was canceled due to the bad wind condition and some troubles in the balloon control system, respectively. However the functions of the FUJIN-1 were evaluated in the ground tests, and the flight model stood by as`flight ready.&#039;In the tests the pointing control system of the telescope, which is the key mechanism for the FUJIN-1, was tested and evaluated to be capable of suppressing the pointing error within 0.4&quot;(σ) which is smaller than the diffraction limit of the FUJIN-1 main telescope. From these results it has been decided that the development of the FUJIN-1 has been completed, and the development of the FUJIN-2, the flight system for longer flight duration in the northern polar region has been started. In this article the outline of the FUJIN project, the FUJIN-1 flight system and the ground test results of the pointing control functionality are introduced.

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Language：Japanese   Publisher：日本惑星科学会  

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DOI： 10.5047/eps.2011.06.019

DOI： 10.1002/2017gl075792_references_DOI_AYHlNGHT3NTnYbsOiyHFMWiDlIi

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