AbeLab related presentations at Meteoroids 2019 International Conference
2 Orals+4 Posters+3 other Orals = 9 presentationsLunar impact flash observation of Geminids and application to lunar impact
monitoring from deep space
Shinsuke Abe, Ryota Fuse (Nihon University), Masahisa Yanagisawa (University of ElectroCommunications), Tetsuya Fukuhara (Rikkyo University), Ryuhei Yamada (University ofAizu), Keisuke Onodera, Satoshi Tanaka, Hajime Yano (ISAS/JAXA), Ryu Funase(University of Tokyo/ISAS)[Oral] Meteoroid Impact Physics
A Lunar Impact Flash (LIF) can be detected as a short duration luminous phenomenon in
VIS and NIR wavelength regions when a meteoroid impacts on the night side of the moon.
The LIF provides absolutely essential for understanding the Earth-Moon meteoroid
environment, especially centimeter to sub-meter sized impactors, which is as a bridge
between visual meteors and small asteroids. Here we report a tremendous impacting rateof Geminids, a dozen LIFs in 2-hours, which were observed on Dec 15 2018 from Nihon
University and the University of Electro-Communications simultaneously. Derived physicalparameters will be discussed. We will also introduce DELPHINUS (DEtection camera forLunar impact PHenomena IN 6U Spacecraft), one of the scientific instruments onboard theworld's smallest spacecraft EQUULEUS (EQUilibriUm Lunar-Earth point 6U Spacecraft) toexplore the Earth-Moon Lagrange point which will be launched by NASA/SLS in 2020.
Reentry physics and upper atmospheric sciences derived from artificial meteors
Shinsuke Abe (Nihon University), Hironori Sahara, Makoto Abo (Tokyo Metropolitan
University), Masa-yuki Yamamoto (Kochi University of Technology), Jun-ichi Watanabe(NAOJ), Toshinori Kuwahara (Tohoku University), Koh Kamachi, Adrien Lemal, Lena
Okajima (ALE Co., Ltd.)[Poster] Future Methods and Techniques
A meteoroid or reentry object interaction with the atmosphere described as a meteor
phenomenon is a complex physics depending on many variables such as entry velocity,
entry angle, composition, shape, density, atmospheric conditions and so on. Artificial
meteors are the best known way to test and calibrate theoretical models of meteoroid
ablation, and has capabilities to investigate upper atmospheric conditions. In 1960s, thefirst artificial meteor experiments were accomplished by using sounding rockets with entry
velocities from 8 to 16 km/s, which provided very important luminous efficiencies
parameters. In 2019, Astro Live Experiences (ALE Co., Ltd.), Tokyo-based startup
company, has developed a small-satellite "ALE-1" which was successfully launched by
JAXA's Epsilon-4 rocket in January. The ALE-1 started descending the orbit altitude from500 to 400 km until below the International Space Station using DOM (De-Orbit
Mechanism), and "a whole new level of entertainment" through the Sky Canvas project will
be held in Spring 2020 over Hiroshima area. We will discuss reentry physics and upper
atmospheric sciences which can be derived from ground-based observations of controlled
artificial shooting stars.

Spectroscopic Study of Luminous Efficiency using Hypervelocity Impact Experimenttoward understanding Lunar Impact Flash Phenomena
Ryota Fuse, Shinsuke Abe (Nihon University), Masahisa Yanagisawa (University of ElectroCommunications), and Sunao Hasegawa (ISAS/JAXA)[Oral] Meteoroid Impact Physics
When a meteoroid impacts on the Moon, a brief flash phenomenon, called as a lunar
impact flash, is observed by ground-based telescope. Its statistical detections canefficiently evaluate the meteoroid size frequency distribution in Cis-lunar space. Luminous
efficiency that is a ratio of impactor's kinetic energy to luminous energy is the mostimportant parameter for the precise meteoroid size estimation. Thus, it is necessary tounderstand the impact flash mechanism and luminous efficiency in various conditions. We
performed hypervelocity impact experiments at JAXA, and measured interactions between
luminous efficiency and ambient atmosphere in various vacuum level. Based on theobtained high-speed spectra (1Mfps: 1μs), it is found that the flash sources are blackbody
radiation from hot ejecta and molecular bands (and atomic lines) from vapor cloud. The
spectrum analysis results reveal that luminous efficiency of μs order depends on ambientpressure, whereas that of ms order does not.

Rotationally resolved visible spectroscopy of (3200) Phaethon and (155140) 2005 UD
Kohei Morita, Shinsuke Abe, Ryo Kato, Kyosuke Sawai (Nihon University), Nicholas
Moskovitz (Lowell Observatory), Fumi Yoshida, Tomoko Arai (PERC, Chiba Institute ofTechnology), Katsuhito Ohtsuka (Tokyo Meteor Network,), Takashi Ito (National
Astronomical Observatory of Japan), Daisuke Kinoshita, Wen-Ping Chen (NationalCentral University)[Poster] Meteoroid Sources(3200) Phaethon classified as B-type spectral taxonomy is known as a parent of Geminid
meteor shower and is thought to be a Comet-Asteroid Transition object (CAT). It is also
shown that (155140) 2005 UD has similar orbital evolution and same B-type spectral
taxonomy which suggests a break-up pair. To investigate surface heterogeneity caused bybreak-up process, rotationally resolved visible spectroscopic observations for Phaethon in2007 and that in 2017 were carried out using 1.0 m Cassegrain telescopes at Lulinobservatory in Taiwan and Kawabe Space Park in Japan, respectively. The samerotationally resolved observation of 2005 UD spectra were obtained by using 4.1 m SOAR
telescope at Chili in 2018. To conclude, Phaethon has C-like positive slope in the visible
wavelength range between 500 and 850 nm which can be seen around equator andsouthern hemisphere terrains. On the other, spectral heterogeneity was not identified for2005 UD which shows B-type negative slope. In this paper, we will discuss possible
hypothesis of break-up mechanism.

Meteor ablation experiments using arc-heated wind tunnel
Atsuki Miyashita, Shinsuke Abe, Homare Matsuyama, Kosuke Ohki, Takumi Ogawa (NihonUniversity), Hironori Sahara (Tokyo Metropolitan University), Lemal Adrien Lemal (ALE Co.,Ltd.), Takayuki Shimoda (JAXA)[Poster] Meteor Physics
The meteoroid ablation process is a complex phenomenon depending on many variables
such as entry velocity, entry angle, composition, shape, density and atmosphericconditions. Meteor ablation tests were carried out using JAXA's arc-heated wind tunnel withartificial samples. With changing distance from the nozzle, we demonstrated several
heating rates between 10.8 and 14.1 MW/m2. NUV-VIS video rate spectroscopy ranging
250 - 1000 nm and the ultra-high-speed imaging with 1µs exposure time. Theseexperiments gave results on time series of atomic emissions, gray body temperatures andluminous efficiencies of samples. In this paper, we will discuss meteor ablation processes
for low velocity meteors such as meteorite and ALE's artificial meteor ablations.

Spectroscopy of Geminid meteor shower
Takumi Ogawa, Shinsuke Abe (Nihon University), Koji Maeda (Miyazaki University/NMS)[Poster] Composition and Physical Properties
The Geminids is the most active annual meteor shower whose parent body is a near-Earthactive asteroid (3200) Phaethon. Since there still remains considerable controversy about
how to generate the Phaethon–Geminid complex, JAXA's flyby mission DESTINY+ isscheduled to be launch in 2022. The sodium depletion in Geminid meteoroids has been
identified which suggested smaller grains deplete sodium during their close encounter withthe Sun. In order to investigate variations of the amount of sodium in Geminids' spectra,
approximately 100 low-resolution spectroscopic observations were carried out using 4K
high-resolution high-sensitive color camera SONY α7s during 2016 - 2018 in Japan. We
will discuss Geminids' spectroscopy in a Mg-Na-Fe ternary graph.

Radar and optical simultaneous observations of faint meteors with MU radar andTomo-e Gozen
Ryou Ohsawa, Akira Hirota, Kohei Morita, Shinsuke Abe, Daniel Kastinen, Johan Kero,Yasunori Fujiwara, Takuji Nakamura, Koji Nishimura, Shigeyuki Sako, Yuto Kojima, Junichi Watanabe[Oral] Future Methods and Techniques
The Earth is surrounded by small dust grains produced by comets and asteroids, parts ofwhich plunge into into the Earth's atmosphere, causing meteor phenomena. A
simultaneous radar and optical observation is promising to constrain a meteor motion and ameteoroid mass at a time. We've started a project to observe faint meteors with Middle andUpper Atmosphere Radar (MU radar), which is operated by Kyoto University, and a widefield CMOS mosaic camera Tomo-e Gozen installed on the 105 cm Kiso Schmidt
telescope, which is in Kiso Observatory, the University of Tokyo. The observations werecarried out in 18--21, April, 2018. From tons of the detected meteors, the simultaneousdetections were extracted in terms of the times, loci, and velocities of the meteors. Finally,
we identified 894 meteor events simultaneously detected in the both sites. The opticalabsolute magnitudes of the simultaneous meteors ranged from about 3--11 mag in the Vband. We confirmed a clear correlation between the meteor brightnesses and the radarcross sections, and derived a conversion function from a radar cross section to an opticalbrightness. The mass and size distributions of meteors detected by MU radar arecompared to literature. The MU and Tomo-e Gozen collaboration will provide statisticalproperties of meteoroids in the range of 0.1--1 mg.

Low-dispersion spectra of lunar impact flashes in 2018 Geminids
Masahisa YANAGISAWA, Yuki UCHIDA, Seiya KURIHARA, Shinsuke ABE, Ryota FUSE,Keisuke ONODERA, Ryuhei YAMADA[Oral] Meteoroid Impact Physics
In the collisions in the solar system, there are many cases where the collisions occur atspeeds exceeding 10 km/s, which are difficult to reproduce in laboratory experiments. Insuch a collision, melting, evaporation, and ionization of silicate, iron, etc. which do notoccur at a speed lower than this occur. Understanding of high-speed collisions
accompanying such processes is an important issue for planetary sciences. However, it is
not clear yet what kind of phenomenon actually occurs. We can approach this problem fromthe observation of lunar impact flashes.
Several research results have been reported on the occurrence frequency andbrightness of lunar impact flashes. However, there are few reports on their spectra. As partof the SAKURA Japan-France joint observation project, that is, the joint observation ofmeteoroids' impacts as lunar seismic sources, we observed the flashes due to thecollisions of December Geminids' meteoroids by simple spectral cameras for visible

wavelength [1]. At the University of Electro-Communications (Chofu, Tokyo, Japan),observations were made with two spectral cameras attached to a Newtonian telescope withan aperture of 450 mm and a focal length of 2025 mm and a Schmidt-Cassegrain
telescope with an aperture of 280 mm and an effective focal length of 920 mm. At Nihon
University (Funabashi, Chiba Prefecture, Japan), observations were carried out mainly withan ordinary movie camera attached to a telescope with a 400 mm aperture.
Thirteen flashes were detected by the observations at the University of ElectroCommunications on 15th December 2018 [2, 3] and nine of them were detected
simultaneously at Nihon University. For those that were not detected at the same time, it isconceivable that there are differences in the sensitivity of the observation devices andtemporary interruptions of observation, but the examination in detail is a future task.
For the bright flashes, their spectra were obtained by comparing their spectral images
with those of comparison stars which were observed every 30 minutes. Our preliminary
results are as follows. Some of the flash spectra could be approximated by blackbody
radiation spectra of about 3000 K. They would be due to the blackbody radiations frommicro-droplets of melted rocks generated at the impacts. On the other hand, there are also
spectra that may be consistent with the higher temperature black bodies, e.g. 6000 K.
There is a possibility that they may be reflections of sunlight by space debris.
It should be noted however that it is not easy to derive reliable spectra because of
atmospheric scintillations and the non-uniform spectral sensitivity over a frame obtained by
the simple spectral movie cameras. Final results will be presented at the Meteoroids 2019
meeting.
References (in Japanese): [1] Kakinuma, F., A spectral camera for observing lunar impactflashes, Master thesis, the University of Electro-Communications, 2016,
http://id.nii.ac.jp/1438/00008427/. [2] Uchida, Y., Low-dispersion spectra of lunar impact
flashes I, Master thesis, the University of Electro-Communications, 2018,
http://id.nii.ac.jp/1438/00008961/. [3] Kurihara, S., Low-dispersion spectra of lunar impact
flashes II, Master thesis, the University of Electro-Communications, 2018,
http://id.nii.ac.jp/1438/00008962/.

Observation of Impact flash at the wavelength of 10 µm using Thermal infrared
cameraTetsuya Fukuhara, Shinsuke Abe, Masahisa Yanagisawa, Ryota Fuse[Oral] Meteoroid Impact Physics
Since Apollo's mission, lunar inner structure models at the depth of <~1000 km have been
proposed based on the observation of seismic signals caused by meteorite impacts.
Accuracy of the model depends on the accuracy of location and epoch of the seismic
source identified by the observation. Ground based observations of impact flash with visible
wavelength recently become valuable to identify its location and epoch precisely. However,the visible observation cannot detect the direct flash except for the event occurring at thenight side. Meanwhile, thermal infrared observation, which detects thermal infraredemission from the target, can observe the impact not only at the nightside but also at thedayside, by which coverage can be expanded. The thermal observation also would detect
residual hot spot caused by the impact. When the temperature variation is derived from thecontinuous observation of the residual hot spot, thermal inertia, from which an energy
budget correlated with size of the crater, would be obtained. Epoch of the impact may beestimated from the thermal relaxation profile even if the impact could not be directlydetected. We propose a thermal infrared camera to be mounted to a future explorer todetect lunar impact flash. The uncooled microbolometer array (UMBA) detecting thethermal infrared wavelengths at 10 µm (8 -14 µm) is a potential thermal detector, whichenable the lightweight and small camera without a cryogenic system. The UMBA for theground telescope with high spatial resolution is applied to a pilot study, which will be carriedout next year at the observatory located at the dry region to avoid the thermal infraredemission being disturbed by the water vapor. A laboratory experiment for the artificial
impact has been carried out in the vacuum environment, and the temperature variation at
the crater has been obtained from the continuous measurement. Thermal inertia
preliminary obtained from the experiment contributes to the insight discussion of the groundobservation.