Yukihiro Takahashi - Academia.edu (original) (raw)

Papers by Yukihiro Takahashi

Research paper thumbnail of Pre-Flight Analysis, Test Evaluation and Flight Verification of the Thermal System of Tohoku University SPRITE-SAT

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN, 2010

The microsatellite SPRITE-SAT developed by Tohoku University was launched in January 2009. Regard... more The microsatellite SPRITE-SAT developed by Tohoku University was launched in January 2009. Regarding the thermal system of SPRITE-SAT, the mathematical model, the parameter determination for the heat transfer coefficients, and the comparison between the estimate and real temperature in flight mode are shown in this paper. The precision of thermal analysis using the simple 7-node model was solved. The estimate error of temperature in orbit is less than 5 degrees Celsius in panels with most of instruments.

Research paper thumbnail of The Evaluation Tests of the Attitude Control System of the 50-kg Micro Satellite RISING-2

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN, 2012

The 50-kg class micro satellite RISING-2 is now under development by Tohoku University and Hokkai... more The 50-kg class micro satellite RISING-2 is now under development by Tohoku University and Hokkaido University. The development is at Flight Model phase and some components are tested to evaluate its specifications. In this paper, the endurance tests using vacuum chamber and thermal test chamber in Tohoku University are described. There was no problem in those tests. In addition, the attitude control accuracy of the RISING-2 was analyzed in the simulation. This simulation based on component specifications and also included noise data. The results show the pointing error angle was less than required error angle.

Research paper thumbnail of Development of a Multi-Spectrum Imager for the S-520 Sounding Rocket

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, SPACE TECHNOLOGY JAPAN, 2009

An S-520 sounding rocket was launched in the summer of 2007 in order to observe magneto electric ... more An S-520 sounding rocket was launched in the summer of 2007 in order to observe magneto electric phenomena in high sky and to verify a new spectroscopic observation method. A Multi-Spectrum Imager (MSI) was developed for the latter aim. The observation device is equipped a spectroscopic camera with a liquid crystal tunable filter and a pointing system to control the pointing direction to take spectroscopic images of a target against the spin of the rocket body. With the successful flight of the sounding rocket, the MSI succeeded in taking and sending approximately 30 pictures and the house keeping data.

Research paper thumbnail of Constellation of Earth Observation Micro-satellites with Multi-spectral High-resolution Telescopes

Tohoku University and Hokkaido University have been developing a series of 50kg-class scientific ... more Tohoku University and Hokkaido University have been developing a series of 50kg-class scientific microsatellites for years. The first micro-satellite was the SPRITE-SAT successfully launched in January 2009 by Japanese H-IIA launcher, which had a mass of about 44 kg and was designed to observe Transient Luminous Events (TLE) in Earth upper atmosphere. SPRITE-SAT was given an operational name of RISING-1 after the launch. Following this satellite, two successor 50kg-class micro-satellites for constellational Earth observation with different types of observation instruments including 5m GSD multi-spectral High-Precision Telescopes (HPT) were initiated. These micro-satellites are namely RISING-2 and RISESAT. The flight model of the RISING-2 is ready for the launch planned in late 2013, and the development of RISESAT will be completed for the launch by the end of Japanese fiscal year of 2013. Both orbits are planned to be sun-synchronous Low Earth Orbit. These micro-satellites will be utilized for constellational Earth observation for planned mission life time of more than two years.

Research paper thumbnail of ISUAL multi-band observations of elves

2011 XXXth URSI General Assembly and Scientific Symposium, 2011

Research paper thumbnail of Energy estimation of electrons producing sprite halos using array photometer data

Journal of Atmospheric and Solar-Terrestrial Physics, 2003

... Rina Miyasato E-mail The Corresponding Author , a , Hiroshi Fukunishi Corresponding Author Co... more ... Rina Miyasato E-mail The Corresponding Author , a , Hiroshi Fukunishi Corresponding Author Contact Information , E-mail The Corresponding Author , a , Yukihiro ... On the other hand, the sprite halos are diffuse glows, which occur at altitudes from 70 to 85 km, following the ...

Research paper thumbnail of Present Status and Scope of TLE and TGF Studies

IEEJ Transactions on Fundamentals and Materials, 2009

Lightning is discharge phenomenon between thunderclouds and the ground, or inside/between thunder... more Lightning is discharge phenomenon between thunderclouds and the ground, or inside/between thunderclouds. However, a new type of atmospheric discharge was found in 1989 by chance: a discharge between thundercloud and ionosphere, named "sprites". After this discovery, similar types of transient luminous events in the middle and upper atmosphere, called TLEs, have been reported. On the other hand, gamma-ray flash radiated from the thundercloud, called TGF, was found in 1994 by satellite observation. Detail characteristics, mechanisms and effects on the atmosphere are not well understood both for TLE and TGF, although the extensive investigations have been carried out experimentally and theoretically for more than a decade. Here we review these phenomena and introduce the latest projects to solve the fundamental scientific problems.

Research paper thumbnail of (1) Sprites are a spectacular type of transient luminous events which occur above thunderstorms immediately after lightning. They have shapes of giant jellyfish, carrots, or columns and last tens of milliseconds. In Earth's atmosphere, sprites mostly emit in

Journal of Geophysical Research, 2009

Research paper thumbnail of On the Global Occurrence and Impacts of Transient Luminous Events (TLEs)

AIP Conference Proceedings, 2009

Based on the first four years of the ISUAL (Imager of Sprites and Upper Atmospheric Lightning) ex... more Based on the first four years of the ISUAL (Imager of Sprites and Upper Atmospheric Lightning) experiment onboard the FORMOSAT-2 satellite, ELVEs are found to be the most abundant type (~80%) of TLEs (transient luminous events), whereas sprites and halos only combine to account for ~20%. The distribution of sprites and halos closely resemble that of the cloud-to-ground lightning. However, nearly 60% of ELVEs occurred over the ocean, a feature indicating that the high peak current lightning is more abundant over the ocean. The global TLE occurrence rates are inferred to be 72, 3.7, and ~1 events/minute, respectively, for ELVEs, halos, and sprites. Comparing with the results from the first three years of the ISUAL experiment reported by Chen et al. (2008) [1], the global occurrence rates for ELVEs and halos are higher due to the adoption of different correction factors. Using these updated TLE rates, the free electron content over an ELVE hot zone is estimated to be elevated by more than 10%. From analyzing ISUAL TLE events without lightning emission contaminations, the average deposited energy in the upper atmosphere by sprites, halos, and ELVEs was found to be 22, 14, and 19 MJ per event, respectively. After factoring in the occurrence rates, in each minute sprites, halos and ELVEs deliver 22, 52 and 1370 MJs of troposphere energy to the upper atmosphere, which are also higher than those reported in Kuo et al. (2008) [2]. However, the global occurrence and energy rates for ELVEs are likely the lower-bound values. A past observation [19] and our ensuing analyses both indicate that the ELVES occurrence rate and, thus, their energy deposition rate in the upper atmosphere should be higher.

Research paper thumbnail of Latitudinal dependence of the solar wind density derived from remote sensing measurements using interplanetary Lyman α emission from 1999 to 2002

Earth, Planets and Space, 2009

The interplanetary Lyman α backscattered emission is an effective tool for remote sensing of the ... more The interplanetary Lyman α 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 α 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 growth 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 2001, 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 ...

Research paper thumbnail of Lightning climatology around Jakarta, Indonesia, based on 13-years SYNOP observation and GSMaP rainfall data

Operational observation in Indonesia, where has much amount of active convections under the tropi... more Operational observation in Indonesia, where has much amount of active convections under the tropical maritime climate with high atmospheric and sea surface temperatures and abundant water vapor supply, showed more than 100-200 days of lightning a year and more than 10 times/km2/year of lightning density. Developed convective systems with lightning (thunderstorms) often generates severe mesoscale phenomena of heavy rainfall, gusty wind, and tornados, as well as lightning strikes at the ground. Indeed, much amount and kinds of serious damages caused by thunderstorms have been reported in Indonesia, e.g., massive blackout and serious damage on electrical devices in urban areas, and forest fires and burn-out of high voltage power lines in rural regions. Although Virts et al. (2013a, 2013b) clearly documented lightning climatology over Indonesia based on TRMM LIS and the World Wide Lightning Location Network (WWLLN) observations, temporal and spatial distributions of lightning activity a...

Research paper thumbnail of Exploration of Jupiter System and Trojan Asteroids

Research paper thumbnail of SPRITE-SAT: a Micro Satellite for Scientific Observation of Transient Luminous Events and Terrestrial Gamma-Ray Flashes

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN, 2010

SPRITE-SAT is a micro satellite in the size of 50 cm cube and weighing 45-kg, designed and develo... more SPRITE-SAT is a micro satellite in the size of 50 cm cube and weighing 45-kg, designed and developed by Tohoku University. Its mission objective is to conduct scientific observation of atmospheric luminous emissions called "sprites" and terrestrial Gamma-ray flushes. Both are recently discovered phenomena and their mechanisms are still under the veil. SPRITE-SAT was developed to achieve significant observations to determine clear models of these mysterious phenomena. On January 23rd, 2009, SPRITE-SAT was successfully launched by JAXA's H-IIA rocket as a piggyback payload of Greenhouse Gas Observation Satellite (GOSAT). The spacecraft is now in a sun-synchronous polar orbit with 670 km altitude from the Earth's surface. This paper describes a general overview of the spacecraft and its mission.

Research paper thumbnail of Highly Precise Pointing Control System on a Balloon-Borne Telescope for Optical Observations of Planets

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN, 2010

A balloon borne telescope is one of the space observation methods by carrying a telescope to the ... more 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.

Research paper thumbnail of The Jupiter Magnetospheric Orbiter and the Trojan Asteroid Explorer in EJSM (Europa Jupiter System Mission)

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN, 2012

EJSM (Europa Jupiter System Mission) is an international Jovian system mission with three spacecr... more EJSM (Europa Jupiter System Mission) is an international Jovian system mission with three spacecraft. Coordinated observation of Jovian magnetosphere is one of the important targets of the mission in addition to icy satellites, atmosphere, and the interior of Jupiter. JAXA will take a role on the magnetosphere spinner JMO (Jupiter Magnetospheric Orbiter), whereas ESA will launch JGO (Jupiter Ganymede Orbiter) and NASA will be responsible for JEO (Jupiter Europa Orbiter). One possibility is to combine JMO with a proposed solar sail mission of JAXA for Jupiter and one of Trojan asteroids. Since Trojan asteroids could be representing raw solid materials of Jupiter or at least outer solar system bodies, involvement of Trojan observation should enlarge the scope and enhance the quality of EJSM.

Research paper thumbnail of Return to Venus of AKATSUKI

Research paper thumbnail of Using Schumann Resonance Measurements for Constraining the Water Abundance on the Giant Planets—Implications for the Solar System's Formation

The Astrophysical Journal, 2012

The formation and evolution of the Solar System is closely related to the abundance of volatiles,... more The formation and evolution of the Solar System is closely related to the abundance of volatiles, namely water, ammonia, and methane in the protoplanetary disk. Accurate measurement of volatiles in the Solar System is therefore important to understand not only the nebular hypothesis and origin of life but also planetary cosmogony as a whole. In this work, we propose a new, remote sensing technique to infer the outer planets water content by measuring Tremendously and Extremely Low Frequency (TLF-ELF) electromagnetic wave characteristics (Schumann resonances) excited by lightning in their gaseous envelopes. Schumann resonance detection can be potentially used for constraining the uncertainty of volatiles of the giant planets, mainly Uranus and Neptune, because such TLF-ELF wave signatures are closely related to the electric conductivity profile and water content.

Research paper thumbnail of Planet-C: Venus Climate Orbiter mission of Japan

Planetary and Space Science, 2007

Earth and Venus • They have almost the same size, but surface environments are completely differe... more Earth and Venus • They have almost the same size, but surface environments are completely different. • What differentiated these planets? How does the climate system work under different conditions?

Research paper thumbnail of A study of the possibility of sprites in the atmospheres of other planets

Journal of Geophysical Research, 2009

Sprites are a spectacular type of transient luminous events which occur above thunderstorms immed... more Sprites are a spectacular type of transient luminous events which occur above thunderstorms immediately after lightning. They have shapes of giant jellyfish, carrots, or columns and last tens of milliseconds. In Earth's atmosphere, sprites mostly emit in red and blue wavelengths from excited N 2 and N 2 + and span a vertical range between 50 and 90 km above the surface. The emission spectra, morphology, and occurrence heights of sprites reflect the properties of the planetary atmosphere they inhabit and are related to the intensity of the initiating parent lightning. This paper presents results of theoretical calculations of the expected occurrence heights of sprites above lightning discharges in the CO 2 atmosphere of Venus, the N 2 atmosphere of Titan, and the H 2-He atmosphere of Jupiter. The expected emission features are presented, and the potential of detecting sprites in planetary atmospheres by orbiting spacecraft is discussed.

Research paper thumbnail of Simultaneous radio and satellite optical measurements of high-altitude sprite current and lightning continuing current

Journal of Geophysical Research, 2006

We report coordinated measurements of lightning and resulting sprites using ground-level magnetic... more We report coordinated measurements of lightning and resulting sprites using ground-level magnetic field sensors (<0.1 Hz to 30 kHz bandwidth) and the ISUAL instrument on the FORMOSAT-2 satellite. These measurements demonstrate two distinct elements of the connection between the radio and optical emissions. First, the quasi-static magnetic field signature is tightly correlated with the low-altitude optical emissions from the lightning flash, indicating that this radio signature is produced by continuing lightning current. Second, in two events with strong postreturn stroke extremely low frequency (ELF) magnetic pulses, the optical emissions demonstrate that there are no observable intensifications of low-altitude optical emissions associated with those pulses. If they were produced by a lightning process, such as an M-component, the connection between optical emissions and current seen in the return stroke and the continuing current suggests they should be visible. However, as has been observed previously, the bright, high-altitude optical emissions associated with the sprite are simultaneous with the ELF pulse. This is strong evidence that these ELF pulses originate in high-altitude electric current in the sprite itself and are not produced by a low-altitude lightning process.

Research paper thumbnail of Pre-Flight Analysis, Test Evaluation and Flight Verification of the Thermal System of Tohoku University SPRITE-SAT

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN, 2010

The microsatellite SPRITE-SAT developed by Tohoku University was launched in January 2009. Regard... more The microsatellite SPRITE-SAT developed by Tohoku University was launched in January 2009. Regarding the thermal system of SPRITE-SAT, the mathematical model, the parameter determination for the heat transfer coefficients, and the comparison between the estimate and real temperature in flight mode are shown in this paper. The precision of thermal analysis using the simple 7-node model was solved. The estimate error of temperature in orbit is less than 5 degrees Celsius in panels with most of instruments.

Research paper thumbnail of The Evaluation Tests of the Attitude Control System of the 50-kg Micro Satellite RISING-2

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN, 2012

The 50-kg class micro satellite RISING-2 is now under development by Tohoku University and Hokkai... more The 50-kg class micro satellite RISING-2 is now under development by Tohoku University and Hokkaido University. The development is at Flight Model phase and some components are tested to evaluate its specifications. In this paper, the endurance tests using vacuum chamber and thermal test chamber in Tohoku University are described. There was no problem in those tests. In addition, the attitude control accuracy of the RISING-2 was analyzed in the simulation. This simulation based on component specifications and also included noise data. The results show the pointing error angle was less than required error angle.

Research paper thumbnail of Development of a Multi-Spectrum Imager for the S-520 Sounding Rocket

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, SPACE TECHNOLOGY JAPAN, 2009

An S-520 sounding rocket was launched in the summer of 2007 in order to observe magneto electric ... more An S-520 sounding rocket was launched in the summer of 2007 in order to observe magneto electric phenomena in high sky and to verify a new spectroscopic observation method. A Multi-Spectrum Imager (MSI) was developed for the latter aim. The observation device is equipped a spectroscopic camera with a liquid crystal tunable filter and a pointing system to control the pointing direction to take spectroscopic images of a target against the spin of the rocket body. With the successful flight of the sounding rocket, the MSI succeeded in taking and sending approximately 30 pictures and the house keeping data.

Research paper thumbnail of Constellation of Earth Observation Micro-satellites with Multi-spectral High-resolution Telescopes

Tohoku University and Hokkaido University have been developing a series of 50kg-class scientific ... more Tohoku University and Hokkaido University have been developing a series of 50kg-class scientific microsatellites for years. The first micro-satellite was the SPRITE-SAT successfully launched in January 2009 by Japanese H-IIA launcher, which had a mass of about 44 kg and was designed to observe Transient Luminous Events (TLE) in Earth upper atmosphere. SPRITE-SAT was given an operational name of RISING-1 after the launch. Following this satellite, two successor 50kg-class micro-satellites for constellational Earth observation with different types of observation instruments including 5m GSD multi-spectral High-Precision Telescopes (HPT) were initiated. These micro-satellites are namely RISING-2 and RISESAT. The flight model of the RISING-2 is ready for the launch planned in late 2013, and the development of RISESAT will be completed for the launch by the end of Japanese fiscal year of 2013. Both orbits are planned to be sun-synchronous Low Earth Orbit. These micro-satellites will be utilized for constellational Earth observation for planned mission life time of more than two years.

Research paper thumbnail of ISUAL multi-band observations of elves

2011 XXXth URSI General Assembly and Scientific Symposium, 2011

Research paper thumbnail of Energy estimation of electrons producing sprite halos using array photometer data

Journal of Atmospheric and Solar-Terrestrial Physics, 2003

... Rina Miyasato E-mail The Corresponding Author , a , Hiroshi Fukunishi Corresponding Author Co... more ... Rina Miyasato E-mail The Corresponding Author , a , Hiroshi Fukunishi Corresponding Author Contact Information , E-mail The Corresponding Author , a , Yukihiro ... On the other hand, the sprite halos are diffuse glows, which occur at altitudes from 70 to 85 km, following the ...

Research paper thumbnail of Present Status and Scope of TLE and TGF Studies

IEEJ Transactions on Fundamentals and Materials, 2009

Lightning is discharge phenomenon between thunderclouds and the ground, or inside/between thunder... more Lightning is discharge phenomenon between thunderclouds and the ground, or inside/between thunderclouds. However, a new type of atmospheric discharge was found in 1989 by chance: a discharge between thundercloud and ionosphere, named "sprites". After this discovery, similar types of transient luminous events in the middle and upper atmosphere, called TLEs, have been reported. On the other hand, gamma-ray flash radiated from the thundercloud, called TGF, was found in 1994 by satellite observation. Detail characteristics, mechanisms and effects on the atmosphere are not well understood both for TLE and TGF, although the extensive investigations have been carried out experimentally and theoretically for more than a decade. Here we review these phenomena and introduce the latest projects to solve the fundamental scientific problems.

Research paper thumbnail of (1) Sprites are a spectacular type of transient luminous events which occur above thunderstorms immediately after lightning. They have shapes of giant jellyfish, carrots, or columns and last tens of milliseconds. In Earth's atmosphere, sprites mostly emit in

Journal of Geophysical Research, 2009

Research paper thumbnail of On the Global Occurrence and Impacts of Transient Luminous Events (TLEs)

AIP Conference Proceedings, 2009

Based on the first four years of the ISUAL (Imager of Sprites and Upper Atmospheric Lightning) ex... more Based on the first four years of the ISUAL (Imager of Sprites and Upper Atmospheric Lightning) experiment onboard the FORMOSAT-2 satellite, ELVEs are found to be the most abundant type (~80%) of TLEs (transient luminous events), whereas sprites and halos only combine to account for ~20%. The distribution of sprites and halos closely resemble that of the cloud-to-ground lightning. However, nearly 60% of ELVEs occurred over the ocean, a feature indicating that the high peak current lightning is more abundant over the ocean. The global TLE occurrence rates are inferred to be 72, 3.7, and ~1 events/minute, respectively, for ELVEs, halos, and sprites. Comparing with the results from the first three years of the ISUAL experiment reported by Chen et al. (2008) [1], the global occurrence rates for ELVEs and halos are higher due to the adoption of different correction factors. Using these updated TLE rates, the free electron content over an ELVE hot zone is estimated to be elevated by more than 10%. From analyzing ISUAL TLE events without lightning emission contaminations, the average deposited energy in the upper atmosphere by sprites, halos, and ELVEs was found to be 22, 14, and 19 MJ per event, respectively. After factoring in the occurrence rates, in each minute sprites, halos and ELVEs deliver 22, 52 and 1370 MJs of troposphere energy to the upper atmosphere, which are also higher than those reported in Kuo et al. (2008) [2]. However, the global occurrence and energy rates for ELVEs are likely the lower-bound values. A past observation [19] and our ensuing analyses both indicate that the ELVES occurrence rate and, thus, their energy deposition rate in the upper atmosphere should be higher.

Research paper thumbnail of Latitudinal dependence of the solar wind density derived from remote sensing measurements using interplanetary Lyman α emission from 1999 to 2002

Earth, Planets and Space, 2009

The interplanetary Lyman α backscattered emission is an effective tool for remote sensing of the ... more The interplanetary Lyman α 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 α 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 growth 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 2001, 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 ...

Research paper thumbnail of Lightning climatology around Jakarta, Indonesia, based on 13-years SYNOP observation and GSMaP rainfall data

Operational observation in Indonesia, where has much amount of active convections under the tropi... more Operational observation in Indonesia, where has much amount of active convections under the tropical maritime climate with high atmospheric and sea surface temperatures and abundant water vapor supply, showed more than 100-200 days of lightning a year and more than 10 times/km2/year of lightning density. Developed convective systems with lightning (thunderstorms) often generates severe mesoscale phenomena of heavy rainfall, gusty wind, and tornados, as well as lightning strikes at the ground. Indeed, much amount and kinds of serious damages caused by thunderstorms have been reported in Indonesia, e.g., massive blackout and serious damage on electrical devices in urban areas, and forest fires and burn-out of high voltage power lines in rural regions. Although Virts et al. (2013a, 2013b) clearly documented lightning climatology over Indonesia based on TRMM LIS and the World Wide Lightning Location Network (WWLLN) observations, temporal and spatial distributions of lightning activity a...

Research paper thumbnail of Exploration of Jupiter System and Trojan Asteroids

Research paper thumbnail of SPRITE-SAT: a Micro Satellite for Scientific Observation of Transient Luminous Events and Terrestrial Gamma-Ray Flashes

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN, 2010

SPRITE-SAT is a micro satellite in the size of 50 cm cube and weighing 45-kg, designed and develo... more SPRITE-SAT is a micro satellite in the size of 50 cm cube and weighing 45-kg, designed and developed by Tohoku University. Its mission objective is to conduct scientific observation of atmospheric luminous emissions called "sprites" and terrestrial Gamma-ray flushes. Both are recently discovered phenomena and their mechanisms are still under the veil. SPRITE-SAT was developed to achieve significant observations to determine clear models of these mysterious phenomena. On January 23rd, 2009, SPRITE-SAT was successfully launched by JAXA's H-IIA rocket as a piggyback payload of Greenhouse Gas Observation Satellite (GOSAT). The spacecraft is now in a sun-synchronous polar orbit with 670 km altitude from the Earth's surface. This paper describes a general overview of the spacecraft and its mission.

Research paper thumbnail of Highly Precise Pointing Control System on a Balloon-Borne Telescope for Optical Observations of Planets

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN, 2010

A balloon borne telescope is one of the space observation methods by carrying a telescope to the ... more 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.

Research paper thumbnail of The Jupiter Magnetospheric Orbiter and the Trojan Asteroid Explorer in EJSM (Europa Jupiter System Mission)

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN, 2012

EJSM (Europa Jupiter System Mission) is an international Jovian system mission with three spacecr... more EJSM (Europa Jupiter System Mission) is an international Jovian system mission with three spacecraft. Coordinated observation of Jovian magnetosphere is one of the important targets of the mission in addition to icy satellites, atmosphere, and the interior of Jupiter. JAXA will take a role on the magnetosphere spinner JMO (Jupiter Magnetospheric Orbiter), whereas ESA will launch JGO (Jupiter Ganymede Orbiter) and NASA will be responsible for JEO (Jupiter Europa Orbiter). One possibility is to combine JMO with a proposed solar sail mission of JAXA for Jupiter and one of Trojan asteroids. Since Trojan asteroids could be representing raw solid materials of Jupiter or at least outer solar system bodies, involvement of Trojan observation should enlarge the scope and enhance the quality of EJSM.

Research paper thumbnail of Return to Venus of AKATSUKI

Research paper thumbnail of Using Schumann Resonance Measurements for Constraining the Water Abundance on the Giant Planets—Implications for the Solar System's Formation

The Astrophysical Journal, 2012

The formation and evolution of the Solar System is closely related to the abundance of volatiles,... more The formation and evolution of the Solar System is closely related to the abundance of volatiles, namely water, ammonia, and methane in the protoplanetary disk. Accurate measurement of volatiles in the Solar System is therefore important to understand not only the nebular hypothesis and origin of life but also planetary cosmogony as a whole. In this work, we propose a new, remote sensing technique to infer the outer planets water content by measuring Tremendously and Extremely Low Frequency (TLF-ELF) electromagnetic wave characteristics (Schumann resonances) excited by lightning in their gaseous envelopes. Schumann resonance detection can be potentially used for constraining the uncertainty of volatiles of the giant planets, mainly Uranus and Neptune, because such TLF-ELF wave signatures are closely related to the electric conductivity profile and water content.

Research paper thumbnail of Planet-C: Venus Climate Orbiter mission of Japan

Planetary and Space Science, 2007

Earth and Venus • They have almost the same size, but surface environments are completely differe... more Earth and Venus • They have almost the same size, but surface environments are completely different. • What differentiated these planets? How does the climate system work under different conditions?

Research paper thumbnail of A study of the possibility of sprites in the atmospheres of other planets

Journal of Geophysical Research, 2009

Sprites are a spectacular type of transient luminous events which occur above thunderstorms immed... more Sprites are a spectacular type of transient luminous events which occur above thunderstorms immediately after lightning. They have shapes of giant jellyfish, carrots, or columns and last tens of milliseconds. In Earth's atmosphere, sprites mostly emit in red and blue wavelengths from excited N 2 and N 2 + and span a vertical range between 50 and 90 km above the surface. The emission spectra, morphology, and occurrence heights of sprites reflect the properties of the planetary atmosphere they inhabit and are related to the intensity of the initiating parent lightning. This paper presents results of theoretical calculations of the expected occurrence heights of sprites above lightning discharges in the CO 2 atmosphere of Venus, the N 2 atmosphere of Titan, and the H 2-He atmosphere of Jupiter. The expected emission features are presented, and the potential of detecting sprites in planetary atmospheres by orbiting spacecraft is discussed.

Research paper thumbnail of Simultaneous radio and satellite optical measurements of high-altitude sprite current and lightning continuing current

Journal of Geophysical Research, 2006

We report coordinated measurements of lightning and resulting sprites using ground-level magnetic... more We report coordinated measurements of lightning and resulting sprites using ground-level magnetic field sensors (<0.1 Hz to 30 kHz bandwidth) and the ISUAL instrument on the FORMOSAT-2 satellite. These measurements demonstrate two distinct elements of the connection between the radio and optical emissions. First, the quasi-static magnetic field signature is tightly correlated with the low-altitude optical emissions from the lightning flash, indicating that this radio signature is produced by continuing lightning current. Second, in two events with strong postreturn stroke extremely low frequency (ELF) magnetic pulses, the optical emissions demonstrate that there are no observable intensifications of low-altitude optical emissions associated with those pulses. If they were produced by a lightning process, such as an M-component, the connection between optical emissions and current seen in the return stroke and the continuing current suggests they should be visible. However, as has been observed previously, the bright, high-altitude optical emissions associated with the sprite are simultaneous with the ELF pulse. This is strong evidence that these ELF pulses originate in high-altitude electric current in the sprite itself and are not produced by a low-altitude lightning process.