Curriculum Vitaes
Profile Information
- Affiliation
- Assistant Professor, Institute of Space and Astronautical Science, Department of Planetary Science, Japan Aerospace Exploration Agencyassistant professor, Department of Earth and Planetary Science, The University of Tokyo
- Degree
- Master of Science(Nagoya University)Doctor of Science(Nagoya University)
- Contact information
- hayakawa
planeta.sci.isas.jaxa.jp - J-GLOBAL ID
- 200901009402364446
- researchmap Member ID
- 1000363026
Research Interests
9Research Areas
2Research History
3Education
2Papers
62-
Advances in Space Research, May, 2024
-
Communications Earth & Environment, 4(1), Sep 27, 2023 Peer-reviewedAbstract Returned samples from Cb-type asteroid (162173) Ryugu exhibit very dark spectra in visible and near-infrared ranges, generally consistent with the Hayabusa2 observations. A critical difference is that a structural water absorption of hydrous silicates is around twice as deep in the returned samples compared with those of Ryugu’s surface, suggesting Ryugu surface is more dehydrated. Here we use laboratory experiments data to indicate the spectral differences between returned samples and asteroid surface are best explained if Ryugu surface has (1) higher porosity, (2) larger particle size, and (3) more space-weathered condition, with the last being the most effective. On Ryugu, space weathering by micrometeoroid bombardments promoting dehydration seem to be more effective than that by solar-wind implantation. Extremely homogeneous spectra of the Ryugu’s global surface is in contrast with the heterogeneous S-type asteroid (25143) Itokawa’s spectra, which suggests space weathering has proceeded more rapidly on Cb-type asteroids than S-type asteroids.
-
Earth, Planets and Space, 75(1), Aug 22, 2023 Peer-reviewedAbstract Zodiacal light (ZL) is sunlight scattered by interplanetary dust particles (IDPs) at optical wavelengths. The spatial distribution of IDPs in the Solar System may hold an important key to understanding the evolution of the Solar System and material transportation within it. The number density of IDPs can be expressed as $$n(r) \sim r^{-\alpha }$$, and the exponent $$\alpha \sim 1.3$$ was obtained by previous observations from interplanetary space by Helios 1/2 and Pioneer 10/11 in the 1970s and 1980s. However, no direct measurements of $$\alpha $$ based on ZL observations from interplanetary space outside Earth’s orbit have been performed since then. Here, we introduce initial results for the radial profile of the ZL at optical wavelengths observed over the range 0.76$$-$$1.06 au by ONC-T aboard the Hayabusa2# mission in 2021-2022. The ZL brightness we obtained is well reproduced by a model brightness, although there is a small excess of the observed ZL brightness over the model brightness at around 0.9 au. The radial power-law index we obtained is $$\alpha = 1.30 \pm 0.08$$, which is consistent with previous results based on ZL observations. The dominant source of uncertainty arises from the uncertainty in estimating the diffuse Galactic light (DGL). Graphical Abstract
-
Earth, Planets and Space, 75(1), Mar 13, 2023 Peer-reviewedAfter delivering its sample capsule to Earth, the Hayabusa2 spacecraft started its extended mission to perform a flyby of asteroid 2001 CC21 in 2026 and rendezvous with asteroid 1998 KY26 in 2031. During the extended mission, the optical navigation camera (ONC) of Hayabusa2 will play an important role in navigation and science observations, but it has suffered from optical deterioration after the spacecraft's surface contact with and sampling of asteroid Ryugu. Furthermore, the sensitivity of the telescopic camera (ONC-T) has continued to decrease for more than a year, posing a serious problem for the extended mission. These are problems that could potentially be encountered by other sample-return missions involving surface contact. In this study, we evaluated the long-term variation of ONC performance over the 6.5 years following the launch in 2014 to predict how it will perform during observations of the two target asteroids in its extended mission (6 and 11 years from the Earth return, respectively). Our results showed several important long-term trends in ONC performance, such as transmission, dark noise level, and hot pixels. During the long cruising period of the extended mission, we plan to observe both zodiacal light and exoplanet transits as additional science targets. The accuracy of these observations is sensitive to background noise level and stray-light contamination, so we conducted new test observations to search for the lowest stray light, which has been found to depend on spacecraft attitude. The results of these analyses and new test observations suggest that the Hayabusa2 ONC will be able to conduct cruising, flyby, and rendezvous observations of asteroids with sufficient accuracy.
-
Science, 379(6634), Feb 24, 2023 Peer-reviewedSamples of the carbonaceous asteroid (162173) Ryugu were collected and brought to Earth by the Hayabusa2 spacecraft. We investigated the macromolecular organic matter in Ryugu samples and found that it contains aromatic and aliphatic carbon, ketone, and carboxyl functional groups. The spectroscopic features of the organic matter are consistent with those in chemically primitive carbonaceous chondrite meteorites that experienced parent-body aqueous alteration (reactions with liquid water). The morphology of the organic carbon includes nanoglobules and diffuse carbon associated with phyllosilicate and carbonate minerals. Deuterium and/or nitrogen-15 enrichments indicate that the organic matter formed in a cold molecular cloud or the presolar nebula. The diversity of the organic matter indicates variable levels of aqueous alteration on Ryugu’s parent body.
Misc.
55-
日本惑星科学会秋季講演会予稿集(Web), 2020, 2020
-
衝撃波シンポジウム講演論文集(CD-ROM), 2019, 2020
-
日本地球惑星科学連合大会予稿集(Web), 2018, 2018
-
Aug, 201750th ISAS Lunar and Planetary Symposium (August 3-4, 2017. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan
-
遊・星・人: 日本惑星科学会誌, 22(3) 152-158, Sep, 2013 Peer-reviewedInvited
-
Abstracts Fall Meeting of the Japanese Society for Planetary Sciences, 2012 19-19, Oct 24, 2012
-
Lunar Planet. Sci., XXXII, 1571-1572, 2001
-
Lunar Planet. Sci., XXXII, 1497-1498, 2001
-
Lunar Planet. Sci., XXXII, 1495-1496, 2001
-
Lunar Planet. Sci., XXXII, 1497-1498, 2001
-
Lunar Planet. Sci., XXXII, 1495-1496, 2001
-
PROCEEDINGS OF THE FOURTH INTERNATIONAL CONFERENCE ON EXPLORATION AND UTILISATION OF THE MOON, 462 187-190, 2000We developed a numerical thermal model of the LUNAR-A penetrator. To make this model precise, we performed two types of experiments. One was to measure thermal conductivity (K) and the heat capacity (Cp) for each component of the penetrator. We successfully obtained these data within 10% in precision. The other was to perform a thermal response experiment for a fully integrated penetrator. With this experiment, we calibrated an initial thermal model which was constructed from the component level data. By inverting the data of the thermal response experiment, we could obtain a final thermal model which is consistent with the component level data and the thermal response experiment as a whole. Numerical simulations of the temperature Field around the penetrator in the lunar regolith indicate that the uncertainty of the thermal model leads to the error of estimating the original temperature gradient of the regolith within 6%.
-
PROCEEDINGS OF THE FOURTH INTERNATIONAL CONFERENCE ON EXPLORATION AND UTILISATION OF THE MOON, 462 107-114, 2000The Japanese lunar penetrator mission, LUNAR-A, is planned to be launched in February 2003. This mission aims to study the lunar interior by using seismometers and heat flow probes on board the lunar penetrators. Two penetrators will be deployed on the lunar surface; one on the nearside, and another on the farside. The seismic study will be made by observing various deep moonquakes at two widely different penetrator sites. fin particular, observations of the amplitudes and travel-times of nearside deep moonquake events at the farside station will reveal core size of the moon, if it exists. Heat flow experiments are also made at two sites in order to better constrain the average lunar heat flow. Obtaining the new data on the core size and the average lunar heat now are crucial to understand the bulk abundance of the siderophile and refractory elements, which in turn are essential to understand the origin of the moon.
-
Proceeding of International Workshop on Penetrometry in the Solar System, 125-136, 2000
-
The Institute of Space and Astronautical Science report, 677 1-21, 2000A hard landing probe "penetrator" has been thought to be a very useful tool for planetary exploration, because it provides cost-effective capability of deploying scientific instruments on planetary surface and subsurface. But development of the penetrator for planetary exploration requires better understanding penetration dynamics in geological materials. The present paper describes some experimental results on the penetrator dynamics obtained during the course of the development of the LUNAR-A penetrator. Special emphasis is placed on understanding the effect of the oblique incidence and the attack angle of the penetrator on penetration depth and a final attitude at the rest position. Many impact experiments into a simulated lunar surface material are made using penetrators 30 mm in diameter, and the penetration characteristics (penetration path length and inflection angle) are investigated as functions of impact velocity, penetrator shape, impact angle and attack angle. The results indicate that the torque applied to the penetrator in cases of the impact with a finite attack angle changes the penetration characteristics significantly. The experimental data also suggests that the impact angle does not have a substantial effect on penetration path length and that the truncation of the nose tip from a conical nose is efficient to stabilize the penetration orientation.
-
PROCEEDINGS OF THE FOURTH INTERNATIONAL CONFERENCE ON EXPLORATION AND UTILISATION OF THE MOON, 462 107-114, 2000The Japanese lunar penetrator mission, LUNAR-A, is planned to be launched in February 2003. This mission aims to study the lunar interior by using seismometers and heat flow probes on board the lunar penetrators. Two penetrators will be deployed on the lunar surface; one on the nearside, and another on the farside. The seismic study will be made by observing various deep moonquakes at two widely different penetrator sites. fin particular, observations of the amplitudes and travel-times of nearside deep moonquake events at the farside station will reveal core size of the moon, if it exists. Heat flow experiments are also made at two sites in order to better constrain the average lunar heat flow. Obtaining the new data on the core size and the average lunar heat now are crucial to understand the bulk abundance of the siderophile and refractory elements, which in turn are essential to understand the origin of the moon.
-
Proceeding of International Workshop on Penetrometry in the Solar System, 125-136, 2000
-
Inst. Space Astron. Sci. Rep. No.677, 677 1-21, 2000A hard landing probe "penetrator" has been thought to be a very useful tool for planetary exploration, because it provides cost-effective capability of deploying scientific instruments on planetary surface and subsurface. But development of the penetrator for planetary exploration requires better understanding penetration dynamics in geological materials. The present paper describes some experimental results on the penetrator dynamics obtained during the course of the development of the LUNAR-A penetrator. Special emphasis is placed on understanding the effect of the oblique incidence and the attack angle of the penetrator on penetration depth and a final attitude at the rest position. Many impact experiments into a simulated lunar surface material are made using penetrators 30 mm in diameter, and the penetration characteristics (penetration path length and inflection angle) are investigated as functions of impact velocity, penetrator shape, impact angle and attack angle. The results indicate that the torque applied to the penetrator in cases of the impact with a finite attack angle changes the penetration characteristics significantly. The experimental data also suggests that the impact angle does not have a substantial effect on penetration path length and that the truncation of the nose tip from a conical nose is efficient to stabilize the penetration orientation.
-
Abstracts Fall Meeting of the Japanese Society for Planetary Sciences, 1999 34-34, Nov 13, 1999
-
MOON AND MARS, 23(11) 1825-1828, 1999Lunar heat flow experiment is planned by using two LUNAR-A penetrators which will be deployed on the near-side and far-side of the lunar surface in 2000. Each penetrator has seven absolute and eleven relative temperature sensors. Impact experiments for real-size penetrator models onto a lunar-regolith analogue target confirmed that the sensors and electronics used in the Lunar-A Heat Flow Experiment can survive the shock loading expected during penetration of the penetrator in a lunar regolith. The calibration experiment demonstrates that the temperature sensors have a resolution of 0.01 degrees and that the thermal conductivity device have 10 % accuracy. In order to determine the heat flow value, we need a good thermal model and numerical simulation for the penetrator and the regolith which in turn requires accurate measurements of thermal properties of the penetrator's components. The current numerical models indicate that we will be able to obtain the lunar heat flow values within 20 to 30 percents in precision with this method. (C) 1999 COSPAR. Published by Elsevier Science Ltd.
-
MOON AND MARS, 23(11) 1825-1828, 1999Lunar heat flow experiment is planned by using two LUNAR-A penetrators which will be deployed on the near-side and far-side of the lunar surface in 2000. Each penetrator has seven absolute and eleven relative temperature sensors. Impact experiments for real-size penetrator models onto a lunar-regolith analogue target confirmed that the sensors and electronics used in the Lunar-A Heat Flow Experiment can survive the shock loading expected during penetration of the penetrator in a lunar regolith. The calibration experiment demonstrates that the temperature sensors have a resolution of 0.01 degrees and that the thermal conductivity device have 10 % accuracy. In order to determine the heat flow value, we need a good thermal model and numerical simulation for the penetrator and the regolith which in turn requires accurate measurements of thermal properties of the penetrator's components. The current numerical models indicate that we will be able to obtain the lunar heat flow values within 20 to 30 percents in precision with this method. (C) 1999 COSPAR. Published by Elsevier Science Ltd.
-
Abstracts Fall Meeting of the Japanese Society for Planetary Sciences, 1998 53-53, Oct 13, 1998
-
Journal of the Japan Society of Precision Engineering, 63(10) 1346-1350, 1997
-
Abstracts Fall Meeting of the Japanese Society for Planetary Sciences, 1996 58-58, Oct 2, 1996
-
Abstracts Fall Meeting of the Japanese Society for Planetary Sciences, 1996 59-59, Oct 2, 1996
-
日本惑星科学会秋季講演会予稿集, 1996 60, Oct, 1996
-
Abstracts Fall Meeting of the Japanese Society for Planetary Sciences, 1995 205-205, Nov 13, 1995The accelerometer onboard LUNAR-A penetrator is developed to estimate the depth of emplacement and information on the physical properties of the lunar regolith. The decceleration record is also indispensable to design the structure of the outer case of lunar penetrator and to investigate quantitatively the shock-resistant capacity for the payload instruments. Investigation of several kinds of sensors' performance and improvement of the data acquisition system are made in order to design the most suitable accelerometer and its electronics for LUNAR-A penetrator. Using the piezoelectric type sensor with annular shear mode, the acceleration profiles with the sufficient accuracy are obtained under the actual flight conditions.
-
JOURNAL OF PHYSICS OF THE EARTH, 41(5) 291-304, 1993In order to study the effectiveness of GPS (Global Positioning System) differential positioning for the deployed Antarctic penetrator, we made fall tests by changing the release altitude at 160, 330, 680, and 1,000 m above the ground. A two-blade helicopter equipped with a Trimble GPS Pathfinder was used in the experiment at the Aoyama Pasture, Hokkaido, in April 1991. As compared with the precise location (0.1 m accuracy) determined by the GPS doubly differenced phase analysis, post-processed 1 min (less than 60 data points during PDOP<10) average of the helicopter hovering GPS differential navigation data was accurate to 10 m for a horizontal location (hovering method). By knowing the release time to an accuracy of 1 s, the impact location can be predicted by tracing the falling trajectory (trajectory method). Thus estimated position was accurate to 30 m against the precise location. As for a height accuracy, there was an error of +/- 10 m in the hovering method. This error further degraded to +/- 20 m when the coordinates of the reference site were replaced by a time-average (1-2 h duration) of the point-positioning results. The above obtained positioning accuracies are enough for a long-range (300 km profile) seismic explosion experiments of each 5-10 km station separation, because the associated errors result only in 0.2% uncertainty on the estimate of P-wave velocity structures.
-
JOURNAL OF PHYSICS OF THE EARTH, 41(5) 291-304, 1993In order to study the effectiveness of GPS (Global Positioning System) differential positioning for the deployed Antarctic penetrator, we made fall tests by changing the release altitude at 160, 330, 680, and 1,000 m above the ground. A two-blade helicopter equipped with a Trimble GPS Pathfinder was used in the experiment at the Aoyama Pasture, Hokkaido, in April 1991. As compared with the precise location (0.1 m accuracy) determined by the GPS doubly differenced phase analysis, post-processed 1 min (less than 60 data points during PDOP<10) average of the helicopter hovering GPS differential navigation data was accurate to 10 m for a horizontal location (hovering method). By knowing the release time to an accuracy of 1 s, the impact location can be predicted by tracing the falling trajectory (trajectory method). Thus estimated position was accurate to 30 m against the precise location. As for a height accuracy, there was an error of +/- 10 m in the hovering method. This error further degraded to +/- 20 m when the coordinates of the reference site were replaced by a time-average (1-2 h duration) of the point-positioning results. The above obtained positioning accuracies are enough for a long-range (300 km profile) seismic explosion experiments of each 5-10 km station separation, because the associated errors result only in 0.2% uncertainty on the estimate of P-wave velocity structures.
Books and Other Publications
2-
Primitive Solar Nebula and Origin of the Planets(Terra Publication Press), 1993
-
Primitive Solar Nebula and Origin of the Planets(Terra Publication Press), 1993
Presentations
217-
55th LPSC, Mar 14, 2024
-
55th LPSC, Mar 12, 2024
Professional Memberships
3-
2009 - Present
-
1992 - Present
Works
6Research Projects
10-
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A), Japan Society for the Promotion of Science, Apr, 2015 - Mar, 2018
-
Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, 2000 - 2002
-
Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, 1997 - 1998
-
Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, 1992 - 1993
-
1984 - 1990
