宇宙科学談話会

ISAS Space Science Colloquium & Space Science Seminar

FY2019

ENGLISH

Europa Clipper Mission and Trajectory Design

Stefano Campagnola(ステファノ カンパニョーラ)
NASA Jet Propulsion Laboratory

Europa is one of the most scientifically interesting targets of the solar system, as it may possess what are thought to be the three necessary ingredients for life: an extensive ocean of liquid water, an energy source, and a suite of biogenic elements. To explore the habitability of Europa, NASA is developing the Europa Clipper mission, currently scheduled to be launched in 2023. Europa resides deep inside the gravity well of Jupiter, in a region of the magnetosphere with many trapped ionized particles that when accelerated to near relativistic speeds result in a radiation environment detrimental to spacecraft electronics; a Europa orbiter mission that would continuously reside in the same radiation environment as Europa would require a large amount of ΔV for an orbit insertion maneuver, and would only return limited science data before being critically exposed to radiation. To mitigate these issues, Europa Clipper will instead use a high number of Europa flybys, connected by resonant and non-resonant transfers. Science data are collected during high-radiation Europa flybys, and returned to Earth during the rest of the highly elliptical Jovian orbits, at a much lower radiation dose exposure. This talk will present an overview of the Europa Clipper Mission, and discuss some of the tour techniques developed to meet the hundreds of science requirements levied on trajectory design.

Place: Bldg. A 4F Conf. room(1432)/ A棟 4F 会議室(1432室)
※通常と時間及び曜日が異なりますので、ご注意下さい。

ENGLISH

Deep and Shallow Learning Models for Autonomous Space Exploration

Roberto Furfaro(ロベルト フルファロ)
University of Arizona

Autonomous and unconstrained exploration of small and large bodies of the solar system requires the development of a new class of intelligent systems capable of integrating in real-time stream of sensor data and autonomously take optimal decisions, i.e. decide the best course of action. For example, future missions to asteroids and comets will require that the spacecraft be able to autonomously navigate in uncertain dynamical environments by executing a precise sequence of maneuvers (e.g. hovering, landing, touch-and-go) based on processed information collected during the close-proximity operations phase. Currently, optimal trajectories are determined by solving optimal guidance problems for a variety of scenarios, generally yielding open-loop trajectories that must be tracked by the guidance system. Although deeply rooted in the powerful tools from optimal control theory, such trajectories are computationally expensive and must be determined off-line, thus hindering the ability to optimally adapt and respond in real-time to 1) uncertainties in the unknown dynamical environment; 2) detected hazards; and 3) science value analysis.
Over the past few years, there has been an explosion of machine learning techniques involving the use of shallow and deep neural networks to solve a variety of problems spanning from object detection to image recognition to natural language processing and sentiment analysis. The recent success of deep learning is due to concurrent advancement of the fundamental understanding on how to train deep architecture, the availability of large amount of data and critical advancements in computing power (e.g. extensive use of GPUs). One can naturally ask the following: how can such techniques help the development of the next generation of robust and adaptive algorithms that may enable autonomous space exploration? In this talk, I will address this problem by presenting a variety of methods and techniques that have been recently developed by my research team in the context of autonomous planetary landing and close proximity operations around small bodies. The methodologies span from supervised learning to deep reinforcement learning and demonstrate that such approaches may be implemented to enable intelligent autonomous systems for both guidance, control and real-time decision-making during the robotic exploration of the solar system."

Place: Bldg. A 1F Nyusatsu Conf. room(1134)/ A棟1F入札・会議室(1134室)

ENGLISH

Active combustion control in a hybrid rocket engine: performance gain from a case study and practical application needs

Carmine Carmicino(カルミネ カルミチーノ)
ISAS/JAXA 宇宙飛翔工学研究系

Hybrid rocket engines are chemical propulsion systems which, in the most common configuration, employ a liquid oxidizer and a solid fuel. Yet essentially preserving performance comparable to the most complicated liquid rocket engines, their typical arrangement involves a series of benefits that can lead to extensive employment as game changing technology in the current space industry. Because of the separation of propellants, throttling can be easily achieved to meet the thrust profile required by the specific mission by controlling the oxidizer mass flow rate; but, to maintain the operation at the optimum mixture ratio (maximum specific impulse), apart from the main oxidizer flow rate, an additional oxidizer stream must be controlled as, for instance, in the configuration of an A-SOFT hybrid rocket. The latter is analyzed from a performance gain perspective compared to a classical hybrid rocket concept, and the requirements of the fuel regression rate measurement sensors needed for a practical implementation are presented.

Place: New Bldg. A 2F Conf. room A (1257) / 新A棟2階会議室A (1257号室)

ENGLISH

Future Planetary Atmospheric, Surface, and Interior Science Using Radio and Laser Links

Sami Asmar
NASA's Jet Propulsion Laboratory, California Institute of Technology

Radio links are used to communicate with spacecraft and also to examine important properties of planetary atmospheres, surfaces, and interior structures by carefully studying small changes in the radio signal's parameters caused by geophysical phenomena. Improving the radio system on the spacecraft and ground stations can lead to additional scientific discoveries. There is a trend to plan for small spacecraft to explore the Solar System in future. Sami Asmar is an experienced radio scientist and leads JPL research initiatives in the science and technology of radio and laser link utilization for planetary exploration.

Place: Bldg. A 2F conf. room(1257) / 新研究管理棟2階会議室A(1257号室)

ENGLISH

The eROSITA View of Stellar Endpoints

佐々木 愛美(Manami SASAKI)
Dr. Karl Remeis Observatory, Bamberg, Friedrich-Alexander-University Erlangen-Nürnberg

eROSITA (extended ROentgen survey with an Imaging Telescope Array) is an X-ray telescope onboard the Russian Spektrum-RG satellite, which will carry out the first imaging all-sky survey in the X-ray band of 0.2 - 10.0 keV. It will thus bridge the gap between the soft X-ray survey, performed with the German Röntgen Satellite (ROSAT, 0.1-2.4keV), and the hard X-ray to gamma-ray surveys of the Rossi X-ray Timing Explorer Mission (3-20 keV), International Gamma-Ray Astrophysics Laboratory (17-60 keV), or Fermi Gamma-ray Space Telescope (1 GeV). In the soft X-ray band (0.5-2 keV), eRASS will be 20-30 times more sensitive than the ROSAT all-sky survey. I will give an overview of the mission and discuss science objectives of eRASS, in particular focussing on the study of galactic X-ray sources.

Place: Bldg.A 1F Nyusatsu Conf.room(1134)/ A棟1F入札・会議室(1134室)

ENGLISH

The first imaging of a black hole shadow with the Event Horizon Telescope(イベントホライズンテレスコープにて撮影された巨大ブラックホールの影)

本間 希樹 (Mareki HONMA)
NAOJ MIZUSAWA

In April 2019, the Event Horizon Telescope (EHT) collaboration has released the first-ever image of a shadow of a super-massive black hole, which is located at the center of M87. The image clearly detected a ring-like structure corresponding to photon sphere surrounding a black hole with central depression of emission, which is the shadow of a black hole.
In this talk, I will briefly introduce the EHT project and then describe the details of observations and results, and will also discuss the future of super-massive black hole study with event-horizon-scale imaging.

Place: A 2F Conf. room(1236) / A棟2階会議場(1236号室)

ENGLISH

Status of LIGO: Past, Present and Future(LIGOの現状と将来像)

山本 博章(Hiroaki YAMAMOTO)
California Institute of Technology LIGO laboratory

After one hundred years since the prediction of the gravitational wave in the theory of general relativity by A. Einstein, the tiny ripple of the space was finally detected by LIGO, Laser Interferometer Gravitational-Wave Observatory, in US, on September 14, 2015, which was radiated by a merger of black holes. The GW signal from a merger of binary neutron starts was detected on August 17, 2017, together with very interesting EM signals by many EM observatories.
After spending a year and half to improve the sensitivity, a new observation run started on April 1, 2019. With the improved sensitivity, GW signals are detected almost one per week, and one signal candidate from a neutron star merger and one from a neutron start - black hole merger have been detected in two months' run.
This talk will cover continuous effects toward the discovery of the GW signals in LIGO and a future plan to make GW signals by ground-based interferometers to probe the astronomy and cosmology.

Place: A 2F Conf. room(1236) / A棟2階会議場(1236号室)
※通常と曜日が異なりますのでご注意ください。

ENGLISH

The Effect of Microlensing On the Observed X-ray Energy Spectra of Gravitationally Lensed Quasars

Henric Krawczynski
Washington University. in St. Louis

The Effect of Microlensing On the Observed X-ray Energy Spectra of Gravitationally Lensed Quasars The Chandra observations of several gravitationally lensed quasars show evidence for Fe K-α fluorescence line emission with time variable line centroid energies.

The time variability may result from the gravitational microlensing of the accretion disk emission, selectively amplifying the X-ray line emission from certain regions very close to the event horizon of the central supermassive black hole.

In this talk, I will present the latest observational results and will discuss the results from modeling the data with a general relativistic ray tracing code and microlensing magnification maps derived from inverse ray shooting calculations.

The simulations cannot fully reproduce the distribution of the detected line energies indicating that some of the assumptions underlying the simulations are not correct, or that the simulations are missing some important physics. I will conclude with a discussion of alternative explanations of the observational results.

Place: A 2F Conf. room(1236) / A棟2階会議場(1236号室)

日本語

国際協力で推進する核融合エネルギー研究開発の新展開

栗原 研一(Kenichi KURIHARA)
国立研究開発法人 量子科学技術研究開発機構 核融合エネルギー研究開発部門 那珂核融合研究所

核融合反応は、太陽などの恒星の中で起こっている反応です。同様の反応を地上で実現する核融合エネルギーは、容易に反応を止められるので安全性に優れている、燃料が枯渇することのない重水素である等の特長を備えており、未来を切り拓くエネルギー源といえます。研究開始は古く、1950年代以降、世界中で様々な核融合の実現方法が考案され、特に原子核がむき出しになる状態-「プラズマ」-を高温にして閉じ込める装置が、試されては消えて行きました。半世紀近くプラズマと格闘した結果、プラズマを磁場で閉じ込める「トカマク方式」が、核融合発電への最有力候補との共通認識が出来上がりました。しかしその装置建設には高度な製造技術と巨額の経費が必要になるため、世界の主要国(日本、欧州、アメリカ、ロシア、中国、韓国、インド)が協力して「国際熱核融合実験炉ITER (発音は「イーター」)」を作ることで合意し、2007年から、南仏で建設を開始しています。目指すは、50万キロワットの核融合エネルギーの発生を世界で初めて実証することです。2025年の運転開始が近づき、構成機器類が着々と出来上がって来ていて、直径30m高さ30mの巨大な本体の組み立ても間近となっている中で、この装置製作と建設が大きく進展しています。一方、このITER計画と並行して、魅力的な核融合発電の早期実現に必要不可欠な技術を開発するため、日欧だけの協力プロジェクトを2007年より推進しています。その一つは直径20m高さ15m超伝導トカマクJT-60SAの建設プロジェクトです。その組立ては順調に進み、いよいよ来年2020年3月に装置が完成、半年の調整後に運転に移行する予定です。完成まで残り1年を切った今、装置の組立ては最終段階に入りました。

講演では、核融合研究の歴史から始まり、エネルギー実現に向けて様々な困難を克服してきたことにも触れます。上記2つの巨大プロジェクト等が大きく進む中、核融合発電実現へ向けた研究開発戦略を紹介します。

Place: A 2F Conf. room(1236) / A棟2階会議場(1236号室)

ENGLISH

The Search for Life in the Galaxy

Paul Hertz
NASA

Humans have always wondered,"Are we alone?"For the first time in history, we have the capability to answer the question scientifically. NASA is engaged in a long term program to first discover, then study, planets orbiting stars beyond our Solar System. Dr. Hertz will explain the scientific search for life in the galaxy, and how NASA's current and future space telescopes will help us find the answer.

Place: A 2F Conf. room(1236) / A棟2階会議場(1236号室)
※通常と曜日が異なりますので、ご注意ください。

ENGLISH

Radio interferometer observations of the nearest high-mass young stellar object in the Orion Nebula

廣田 朋也(Tomoya HIROTA)
国立天文台水沢VLBI観測所

The Orion Nebula is known as the nearest (420 pc from the Sun) site of active high-mass star-formation. In particular, a bright infrared nebula called Kleinmann-Low object located at its central region has been extensively observed as the best laboratory for high-mass star-formation studies at the highest spatial resolution achievable with various astronomical instruments. Here we report recent observational results for one of the high-mass young stellar objects (HM-YSOs), radio source I, by using VERA (VLBI Exploration of Radio Astrometry) and ALMA (Atacama Large Millimeter/Submillimeter Array). We will discuss formation processes of this HM-YSO through dynamical properties of circumstellar disk and outflow driven by the magneto-centrifugal disk wind traced by centimeter/millimeter/submillimeter H2O and SiO maser lines.

Place: A 2F Conf. room(1236) / A棟2階会議場(1236号室)

日本語

「あかり」近赤外線分光観測による小惑星の含水鉱物探査

臼井 文彦(Fumihiko USUI)
神戸大学大学院理学研究科 惑星科学研究センター

小惑星における含水鉱物の存在を調べることは、太陽系の成り立ち、特に熱的な変遷を知る上で重要である。含水鉱物は液体の水と無水鉱物が反応して生成されるが、水の昇華温度以上でも比較的安定であるため、水の存在を示す重要なトレーサーである。含水鉱物は近赤外線の波長2.7 um付近に吸収フィーチャーを持つことが知られているが、この波長域は地球大気の吸収のために、地上望遠鏡では観測できていなかった。我々は赤外線天文衛星「あかり」を用いて、地球大気に影響されることなく小惑星の近赤外線分光観測を行い、小惑星66天体のスペクトルを得ることに成功した。その結果、多くのC型小惑星には含水鉱物に起因する顕著な吸収が見られること、一方ほとんどのS型小惑星にはそのような吸収が見られないことがわかった。本講演では、「あかり」による小惑星の近赤外線分光観測の概要とその結果から考えられる小惑星の形成進化過程について紹介し、さらに天文観測と小惑星探査の関係性について議論する。

Place: A 2F Conf. room(1236) / A棟2階会議場(1236号室)

ENGLISH

Laboratory astrophysics with electron beam ion traps

J. R. Crespo López-Urrutia
Max-Planck-Instutite fuer Kernphysik

At very high temperatures, atomic physics becomes the physics of highly charged ions (HCI). The presence of a few, still bound, electrons makes HCI from'metals'efficient absorbers and emitters of X rays, EUV, VUV and optical photons. Clear spectroscopic signatures from HCI are identifiably even at locations where the dominant light chemical elements are fully stripped, such as in AGN. Within the radiative zones of stars, HCI have a dominant contribution to the opacity. Future X-ray missions will provide unprecedented amounts of high-resolution spectral data. This will challenge our current atomic physics modelling of HCI, which is still limited by theoretical uncertainties and a lack of laboratory benchmarks for spectral models. Presently, existing laboratory data show clear disagreements with widely used astrophysical codes, call-ing for updating models. At the same time, the further development of atomic structure theory needed to generate data on collisional excitation and recombination, as well as photon-driven processes in astrophysical plasmas benefits from laboratory studies of HCI. Improving such benchmark measurements is an important task, ahead of the upcoming XRISM Resolve, Athena and Arcus missions. Electron beam ion traps (EBITs) are compact devices that produce, trap and excite HCI from N3+ (N IV) to U91+ (U XLII) under well-defined, steady-state conditions of charge state as well as excitation by a monoenergetic electron beam. They are sources for high-resolution spec-troscopy in all photon energy ranges. Dielectronic recombination, electron-impact excitation, and charge exchange are studied in detail using them.
Together with free-electron lasers and synchrotron radiation sources, EBITs have enabled soft X-ray laser spectroscopy, reaching by now up to the K-shell transitions of heavy elements.

4/9 14:00-17:00: Tutorial(1)
4/10 9:30-12:30: Tutorial(2)
4/10 14:00-16:00: Free discussion
(Room: Research and Administration Building , 6F, 1639)

 

実験室宇宙物理学の世界的拠点であるマックスプランク核物理学研究所において研究グループを率いるJose Crespo López-Urrutia氏より、電子ビームイオントラップ(EBIT)を用いたプラズマ実験の最先端を紹介いただきます。 また来所に合わせて2日間に渡るレクチャーを以下のスケジュールで行います。 ご都合のつく方はこちらも合わせてご参加ください。

4/9 14:00-17:00: Tutorial(1)
4/10 9:30-12:30: Tutorial(2)
4/10 14:00-16:00: Free discussion
(Room: Research and Administration Building , 6F, 1639)

Place: Shin-A 2F Conf. room A (1257) / 新A棟2階会議室A(1257号室)