A5015516568- Planetary Science and Exploration
- Astro and Planetary Science
- Solar and Space Plasma Dynamics
- Space Exploration and Technology
- Space Science and Extraterrestrial Life
- Ionosphere and magnetosphere dynamics
- Space exploration and regulation
- Geology and Paleoclimatology Research
- Geophysics and Gravity Measurements
- SARS-CoV-2 detection and testing
- Spacecraft Design and Technology
- Spaceflight effects on biology
- Meteorological Phenomena and Simulations
- Radio Astronomy Observations and Technology
- Satellite Communication Systems
- SARS-CoV-2 and COVID-19 Research
- GNSS positioning and interference
- Atmospheric and Environmental Gas Dynamics
- Geomagnetism and Paleomagnetism Studies
- Space Satellite Systems and Control
- Scientific Research and Discoveries
- Atmospheric aerosols and clouds
- Atmospheric Ozone and Climate
- Stellar, planetary, and galactic studies
- COVID-19 diagnosis using AI
Hokkaido University
2017-2025
University of Arizona
2024-2025
Kyoto Sangyo University
2016-2024
Ohta Nishinouchi Hospital
2022
Japan Aerospace Exploration Agency
2013-2016
Institute of Space and Astronautical Science
2013-2016
The University of Tokyo
2010-2012
Tokyo University of Science
2012
Chiba University
2006
AKATSUKI is the Japanese Venus Climate Orbiter that was designed to investigate climate system of Venus. The orbiter launched on May 21, 2010, and it reached December 7, 2010. Thrust applied by orbital maneuver engine in an attempt put into a westward equatorial orbit around with 30-h period. However, this operation failed because malfunction propulsion system. After failure, spacecraft orbited Sun for 5 years. On 2015, once again approached insertion successful, whereby apoapsis ~440,000 km...
After the arrival of Akatsuki spacecraft Japan Aerospace Exploration Agency at Venus in December 2015, radio occultation experiment, termed RS (Radio Science), obtained 19 vertical profiles Venusian atmosphere by April 2017. An onboard ultra-stable oscillator is used to generate stable X-band downlink signals needed for experiment. The quantities be retrieved are atmospheric pressure, temperature, sulfuric acid vapor mixing ratio, and electron density. Temperature were successfully down ~ 38...
Abstract The existence of large stationary gravity waves was discovered during Akatsuki's first observation sequence in 2015. In this study, the further detection brightness temperature images over a 1.5 year period is reported. periodically appeared mostly above four specific highland regions low latitudes when these were local afternoon. wave amplitudes attenuated after locations passed beyond evening terminator, and tended to slowly drift eastward their lifetimes. appearances depend not...
Abstract Thermal tides in the Venus atmosphere are investigated by using a GCM named as AFES‐Venus. The three‐dimensional structures of wind and temperature associated with thermal obtained our model fully examined compared observations. result shows that distributions depend complexly on latitude altitude cloud layer, mainly because they consist vertically propagating trapped modes zonal wave numbers 1–4, each which predominates different latitudes altitudes under influence mid‐...
Abstract We present distributions of the zonal-mean temperature and static stability in Venusian atmosphere obtained from Venus Express Akatsuki radio occultation profiles penetrating down to an altitude 40 km. At latitudes equatorward 75°, derived observed is consistent with previous in-situ measurements that there a low-stability layer at altitudes 50–58 km highly moderately stratified layers above 58 below 50 km, respectively. Meanwhile, poleward extends 42 which has been unreported...
The ultraviolet imager (UVI) has been developed for the Akatsuki spacecraft (Venus Climate Orbiter mission). UVI takes (UV) images of solar radiation reflected by Venusian clouds with narrow bandpass filters centered at 283 and 365 nm wavelengths. There are absorption bands SO2 unknown absorbers in these wavelength regions. UV provide spatial distribution absorber around cloud top altitudes. also allow us to understand morphologies haze properties. Nominal sequential 2-h intervals used...
Abstract The 4‐day and 5‐day waves observed at the cloud top in Venus atmosphere are expected to play important roles maintenance of general circulation. However, they have not been reproduced circulation models (GCMs) so far, their structures excitation mechanisms remain poorly understood. Using an improved GCM, we succeeded reproducing planetary‐scale 3.3‐day 5.8‐day waves, which considered correspond respectively. We also obtained 4.8‐day wave, whose structure is similar that wave....
Wastewater-based epidemiology is expected to be able identify SARS-CoV-2 variants at an early stage via next-generation sequencing. In the present study, we developed a highly sensitive amplicon sequencing method targeting spike gene of SARS-CoV-2, which allows for viral genomes from wastewater containing low amount virus. Primers were designed amplify relatively long region (599 bp) around receptor-binding domain in gene, could distinguish initial major concern. To validate methodology,...
International mass gathering events, such as the Olympic and Paralympic Games, face risk of cross-border transmission infectious diseases. We previously reported that wastewater-based epidemiology (WBE), which has attracted attention a COVID-19 surveillance tool, was implemented in Tokyo 2020 Village to gain comprehensive understanding incidence village. In present study, we explored quantitative association wastewater viral load clinically confirmed cases various areas From July 14 through...
The M-MATISSE mission, currently in its Phase A study by the European Space Agency (ESA), is a Medium-class (M7) candidate that aims to explore complex interactions between Mars' magnetosphere, ionosphere, and thermosphere (MIT coupling). This two-spacecraft comprising identical payloads on board "Henry" "Marguerite", will investigate how these are influenced space weather lower atmosphere. spacecraft follow different orbits with apocenters at 3,000 km 10,000 altitude, respectively,...
The Longwave Infrared Camera (LIR) is one of a suite cameras onboard the Venus orbiter Akatsuki. It will take images thermal radiation in wavelength range 8–12 µm emitted by cloud tops. use an uncooled micro-bolometer array as infrared image sensor makes LIR lightweight, small and low-power consumption instrument with required noise equivalent temperature difference 0.3 K. Temperature horizontal wind fields at cloud-top be retrieved for both dayside nightside equal quality. This provide key...
Radial variations of the amplitude and energy flux compressive waves in solar corona were explored for first time using a spacecraft radio occultation technique. By applying wavelet analysis to frequency series taken at heliocentric distances 1.5–20.5 RS (solar radii), quasi-periodic density disturbances detected almost all distances. The period ranges from 100 2000 s. fractional fluctuation increases with distance reaches ∼30% around 5 RS, implying that nonlinearity wave field is...
Radio scintillation observations have been unable to probe flow speeds in the low corona where scattering of radio waves is exceedingly strong. Here we estimate outflow continuously from vicinity Sun outer (heliocentric distances 1.5–20.5 solar radii) by applying strong theory scintillations for first time, using Akatsuki spacecraft as source. Small, nonzero were observed over a wide latitudinal range quiet-Sun corona, suggesting that supply plasma closed loops wind occurs an extended area....
Abstract Unlike the polar vortices observed in Earth, Mars and Titan atmospheres, Venus vortex is warmer than midlatitudes at cloud-top levels (∼65 km). This warm zonally surrounded by a cold latitude band located ∼60° latitude, which unique feature called ‘cold collar’ atmosphere. Although these structures have been numerous previous observations, formation mechanism still unknown. Here we perform numerical simulations of atmospheric circulation using general model, succeed reproducing...
Since insertion into orbit on December 7, 2015, the Akatsuki orbiter has returned global images of Venus from its four imaging cameras at eleven discrete wavelengths ultraviolet (283 and 365 nm) near infrared (0.9–2.3 µm), to thermal (8–12 µm) a near-equatorial orbit. The Express Pioneer Orbiter missions have also monitored planet for long periods but polar or near-polar orbits. wavelength coverage views differ all three missions. In reflected light, reveal features seen cloud tops (~ 70 km...
Abstract By using the vertical temperature profiles obtained by radio occultation measurements on European Space Agency (ESA)’s Venus Express, wavenumber spectra of small-scale fluctuations that are thought to be manifestations gravity waves studied. Wavenumber covering wavelengths 1.4–7.5 km were for two altitude regions (65–80 and 75–90 km) seven latitude bands. The show a power-law dependence high-wavenumber side with logarithmic spectral slope ranging from −3 −4, which is similar...
Abstract Vertical wavenumber spectra of Martian gravity waves were obtained for the altitude range 3–32 km from temperature profiles acquired by Mars Global Surveyor (MGS) radio occultation experiments. The spectra, which cover vertical wavelengths 2.5 to 15 km, generally show a decline spectral density with similar those in terrestrial stratosphere and mesosphere. power-law index is typically around −3 except near low-wavenumber end, frequently lie along theoretical spectrum saturated...
The first year (December 2015 to November 2016) of IR2 after Akatsuki's successful insertion an elongated elliptical orbit around Venus is reported with performance evaluation and results data acquisition. single-stage Stirling-cycle cryo-cooler has been operated various driving voltages achieve the best possible cooling under given thermal environment. A total 3091 images (1420 dayside at 2.02 μm 1671 night-side 1.735, 2.26, 2.32 μm) were acquired in this period. Additionally, 159 images,...
Abstract Temperature profiles of the Venus atmosphere obtained by Akatsuki radio occultation measurements showed a prominent local time dependence above 65‐km altitude at low latitudes equatorward 35°. A zonal wavenumber 2 component is predominant in temperature field, and its phase (i.e., isothermal) surfaces descend with time, suggesting downward propagation. general circulation model (GCM) for atmosphere, AFES‐Venus, reproduced time‐dependent thermal structure qualitatively consistent...
The electron density distribution in the vicinity of lunar surface was explored with radio occultation technique using a subsatellite on SELENE mission. Although measurements suffer from contamination by terrestrial ionosphere and interplanetary plasma, an analysis more than 300 provides adequate statistics reveals general trend. result suggests that dense covering whole sunlit side, as suggested Soviet Luna 19 22 missions, does not exist. However, weak signatures enhancement densities order...
The Radio Science experiment (RS) in the Akatsuki mission of JAXA aims to determine vertical structure Venus atmosphere, thereby complementing imaging observations by onboard instruments. physical quantities be retrieved are distributions atmospheric temperature, electron density, H2SO4 vapor and small-scale density fluctuations. uniqueness RS as compared previous radio occultation experiments at is that low latitudes can probed many times thanks near-equatorial orbit. Systematic sampling...