• 한국광물학회지
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• 제24권1호
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• pp.31-36
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• 2011

운석은 모암인 소행성(asteroid)이나 미세소행성(planetesimal)에서 충돌에 의해 분리된 후, 태양계 내의 공간을 배회하다가 지구의 중력에 이끌려 지표에 떨어진 후 수집된 돌덩이다. 따라서 생성 초기의 지구를 포함하는 태양계 내 지구형 행성의 생성 초기와 진화과정을 규명하려면 원시 태양계의 정보를 간직하고 있는 운석의 물리/화학적 분석이 반드시 필요하다. 특히 열잔류자화(thermoremanent magnetization, TRM) 대비 포화등온잔류자화(saturation isothermal remanent magnetization, SIRM)의 비율과 자화를 유도하는 자기장 강도의 상관관계를 이용하면 운석이 함유하는 자성광물을 판별할 수 있다. TRM/SIRM 비를 이용하여 2종류의 미분화운석(H5 Richardton, LL6 St. Severin)과 2종류의 화성기원 분화운석(ALH84001, DaG476)에 대해 자성광물 판별을 시도하였다. 실험 결과 H5 Richardton, LL6 St. Severin, ALH84001, DaG476의 주 자성광물이 각각 카마사이트, 테트라테나이트, 자철석, 크롬티탄함유철석임을 판별하였다.

• 천문학회보
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• 제41권2호
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• pp.49.2-49.2
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• 2016

The number of discovery of asteroids with peculiar rotational states has recently increased, and hence a novel approach for lightcurve analysis is considered to be critical. In order to investigate objects such as Non-Principal Axis (NPA) rotator, we selected a NPA candidate, (5247) Kryolv as our target considering its Principal Axis Rotation (PAR) code and the visibility in early 2016. The observations of Krylov were made using Korea Microlensing Telescope Network (KMTNet) 1.6 m telescopes installed at the three southern sites with TO (Target of Opportunity) observation mode. We conducted R-band time-series photometry over a total of 51 nights from January to April 2016 with several exposures during each allocated run. The ensemble normalization photometry was employed using the AAVSO Photomtric All-Sky Survey (APASS) catalog for the standardization. We successfully confirmed its NPA spin state based on the deviation from the reduced lightcurve, and thus Krylov is recorded as the first NPA rotator of its kind in the main-belt, with its precession and rotation periods, $P{\varphi}=81.18h$ and $P_{\Psi}=67.17h$, respectively. In this paper, we present the spin direction, the 3D shape model and taxonomy of the newly confirmed NPA asteroid (5247) Krylov.

• 천문학회지
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• 제49권1호
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• pp.37-44
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• 2016

The Korea Microlensing Telescope Network (KMTNet) is a wide-field photometric system installed by the Korea Astronomy and Space Science Institute (KASI). Here, we present the overall technical specifications of the KMTNet observation system, test observation results, data transfer and image processing procedure, and finally, the KMTNet science programs. The system consists of three 1.6 m wide-field optical telescopes equipped with mosaic CCD cameras of 18k by 18k pixels. Each telescope provides a 2.0 by 2.0 square degree field of view. We have finished installing all three telescopes and cameras sequentially at the Cerro-Tololo Inter-American Observatory (CTIO) in Chile, the South African Astronomical Observatory (SAAO) in South Africa, and the Siding Spring Observatory (SSO) in Australia. This network of telescopes, which is spread over three different continents at a similar latitude of about -30 degrees, enables 24-hour continuous monitoring of targets observable in the Southern Hemisphere. The test observations showed good image quality that meets the seeing requirement of less than 1.0 arcsec in I-band. All of the observation data are transferred to the KMTNet data center at KASI via the international network communication and are processed with the KMTNet data pipeline. The primary scientific goal of the KMTNet is to discover numerous extrasolar planets toward the Galactic bulge by using the gravitational microlensing technique, especially earth-mass planets in the habitable zone. During the non-bulge season, the system is used for wide-field photometric survey science on supernovae, asteroids, and external galaxies.

• 천문학회보
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• 제42권2호
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• pp.50.1-50.1
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• 2017

The Non-Principal Axis (NPA) rotators can be clues to spin evolutionary processes of asteroids because their excited spin states evolve due to either internal or external forces. The NPA rotation of (5247) Krylov was confirmed by Lee et al. (2017) based on KMTNet photometric observations during the 2016 apparition. We conducted follow-up observations in 2017 apparition using the 0.6-2.1m telescopes in the northern hemisphere to determine the spin state and shape model of this asteroid. We found that it is rotating in the Short Axis Mode (SAM) based on the determined rotation period ($P_{\psi}=374.6hr$) and precession period ($P_{\phi}=67.48hr$). The greatest and intermediate principal inertia moments are nearly the same as $I_b/I_c=0.94$, but the smallest principal inertia moments are nearly half that of the others, $I_a/I_c=0.43$. This ratio of principal inertia moments suggests that dynamically equivalent shape of this asteroid is close to that of a prolate ellipsoid. In this presentation, we will provide the physical model of (5247) Krylov to discuss its possible spin evolutionary processes that acted on its spin.

• Journal of Astronomy and Space Sciences
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• 제5권2호
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• pp.129-141
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• 1988

제한 3체 문제의 수치해를 이용하여 태양-목성계와 지구-달계의 $L_5$점 근처에서 각각 490여개, 1,600여개의 주기 궤도를 구하였다. 태양-목성계의 경우에서는 주기의 증가에 따라 에너지와 주기 궤도 크기가 단조롭게 커졌다. 그러나 지구-달계에서의 주기 궤도 모양은 복잡하고 변곡점이 나타나며 서로 겹치는 경우도 있다. 또한, 지구-달계에서 단일주기에 3개의 에너지가 동시 대응하는 영역이 존재하며 이 영역에소는 주기와 에너지가 반비례하는 구역이 있다. 태양-목성계의 $L_5$ 점 근처에서 목성의 중력 섭동 외의 기타의 작은 섭동에 의해 불안정한 주기 궤도가 될 수 있는 영역이 존재 가능하다. 이 영역 중 $L_5$점(5.2AU)에 가장 가까운 지역들이 a~5.12AU와 a~5.29AU 근처인데, 이 곳에는 이심률과 궤도 경사각이 작은 Trojan 소행성들이 존재하기 어렵다고 할 수 있다.

• Animal Systematics, Evolution and Diversity
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• nspc5호
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• pp.47-60
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• 2005

2004년 6월 29일부터 7월 1일까지 이루어진 한국동물분류학회 창립 20주년 기념 합동채집회에서 벌포와 초평, 수품, 회동, 서망, 북위 $34^{\circ}11'N$과 동경 $126^{\circ}21'E$ 등, 진도의 6개 지역에서 채집되어 동정된 극피동물은 4강 10목 13과 20종으로서 바다나리가 1목 1과 1종, 불가사리류가 3목 4과 7종. 거미불가사리 류가 2목 3과 5종, 성게류가 1목 2과 4종, 해삼류가 3목 3과 3종이었다. 이들 중 바다니리류 1종, 가시예쁜갯고사리 (Antedon serrata)와 불가사리류 2종, 도우손햇님불가사리 (Solaster dawsoni)와 일본불가사리 (Distolasterias nipon), 그리고 거미불가사리류 1종, 나무거미불가사리 (Astrodendrum sagaminum)는 진도에서 처음 기록되는 종이며 1종의 한국 미기록 해삼류 (Pseudocnus sp.)가 포함된다. 과거기록을 포함하여 총 31종의 종 목록을 작성하였으며, 분포형과 종 출현양상을 근거로 진도 해역의 극피동물상을 논하였다.

• 천문학회보
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• 제43권2호
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• pp.44.4-45
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• 2018

(4179) Toutatis (Toutatis hereafter) is one of the Near-Earth Asteroids which has been studied most rigorously not only via ground-based photometric, spectroscopic, polarimetric, and radar observations, but also via the in-situ observation by the Chinese Chang'e-2 spacecraft. However, one of the most fundamental physical properties, the geometric albedo, is less determined. In order to derive the reliable geometric albedo and further study the physical condition on the surface, we made photometric observations of Toutatis near the opposition (i.e., the opposite direction from the Sun). We thus observed it for four days on 2018 April 7-13 using three 1.6-m telescopes, which consist of the Korean Microlensing Telescope Network (KMTNet). Since the asteroid has a long rotational period (5.38 and 7.40 days from Chang'e-2, Zhao et al., 2015), the continuous observations with KMTNet matches the purpose of our photometric study of the asteroid. The observed data cover the phase angle (Sun-asteroid-observer's angle) of 0.65-2.79 degree. As a result, we found that the observed data exhibited the magnitude changes with an amplitude of ~0.8 mag. We calculated the time-variable geometrical cross-section using the radar shape model (Hudson & Ostro 1995), and corrected the effect from the observed data to derive the geometric albedo. In this presentation, we will present our photometric results. In addition, we will discuss about the regolith particles size together with the polarimetric properties based on the laboratory measurements of albedo-polarization maximum.

• 한국지반공학회논문집
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• 제38권9호
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• pp.19-33
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• 2022

우주 행성 지반 탐사 미션은 1970년대에 활발하게 이루어졌으나 1990~2000년대에는 예산 문제로 쇠퇴기를 맞았다. 그러나 미래에 지구 자원 고갈에 대비하고 헬륨-3 및 희토류와 같이 우주에는 풍부하지만 지구에는 부족한 자원을 탐사하기 위해서는 우주 자원 탐사는 필수적이다. 또한, 우주 기술 발전은 미래 산업 발전의 원동력이 된다. 따라서 우주 자원 탐사 및 활용을 위해 최근 10년 동안 우주 행성 탐사를 위한 선진국 간의 기술 경쟁이 다시 가속화되고 있다. 이 우주 행성 자원 탐사/채굴 및 기지 건설 미션을 위해서는 지반 탐사가 필요하며 현재까지 달에 대한 탐사 미션으로는 Apollo 미션과 LUNA 미션, Chang'E 미션 등이 있고 해당 미션에서 유인 및 로버를 활용한 무인 시추 미션을 수행하였다. 화성 미션으로는 Viking, Spirit/Opportunity, Phoenix, Perseverance 미션, 소행성 탐사 미션은 하야 부사(Hyabusa) 미션이 있었다. 본 논문에서는 현재까지 수행된 우주 행성 광물 자원 탐사 기술에 대해 서술하고 향후 우리나라의 기술과제에 대하여 서술하였다.

• 천문학회보
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• 제46권1호
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• pp.44.2-45
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• 2021

As implied by the zodiacal light and spacecraft impact measurements, the space between large bodies in our Solar System is filled with interplanetary dust particles (IDPs). IDPs give us deeper insight into the composition and evolution of the Solar System, as well as being a crucial reference for extrasolar research. IDPs can be interpreted as bearers of carbon and organic materials, and thus, their interaction with Earth can be considered as important factors for the birth of terrestrial life. One of the key routes of IDPs entering Earth is via meteoroid streams (Love and Brownlee 1993). The Geminid meteoroid stream is a notable example. Together with its source asteroid (3200) Phaethon, the Phaethon-Geminid stream complex (PGC) (Whipple 1983; Gustafson 1989) can potentially provide information on the properties and evolution of IDPs in near-Earth space. DESTINY+* is a JAXA/ISAS spacecraft planned to launch in 2024 to explore the physical and chemical features of near-Earth IDPs and uncover the dust ejection mechanism of active near-Earth asteroids, especially Phaethon (Arai et al. 2018). Previous studies on the dust ejection mechanism of Phaethon have various degrees of success in explaining the ejection of submillimeter particles and try to recreate the dust replenishment rate of the Geminid stream. However, none of them are satisfactory for explaining the observed Geminid stream, especially for larger particles of a millimeter and centimeter scales. Inspired by the discovery of rotational mass shedding in the Main Belt region (Jewitt et al., 2014), we investigate a dust ejection scenario by rotational instability on Phaethon. Using the N-body integrator MERCURY6 (Chambers 1999; modified by Jeong 2014), we performed a long-term integration of dust particles of various sizes ejected at ~1 m/s. Through this process, we discuss the implications Phaethon's rotation may have on its ejection, the formation and evolution of IDP by this mechanism, and contribute to the DESTINY+ mission.

• 천문학회보
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• 제45권1호
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• pp.45.2-46
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• 2020

Various processes, such as space weathering and granular convection, are occurring on asteroids' surfaces. Estimation of the surface exposure timescale is essential for understanding these processes. The Hayabusa mission target asteroid, (25143) Itokawa (Sq-type) is the only asteroid whose age is estimated from remote sensing observations as well as sample analyses in laboratories. There is, however, an unignorable discrepancy between the timescale derived from these different techniques. The ages estimated based on the solar flare track density and the weathered rim thickness of regolith samples range between 102 and 104 years [1][2]. On the contrary, the ages estimated from the crater size distributions and the spectra cover from 106 to 107 years [3][4]. It is important to notice that there is a common drawback of both age estimation methods. Since the evidence of regolith migration is found on the surface of Itokawa [5], the surficial particles would be rejuvenated by granular convection. At the same time, it is expected that the erasure of craters by regolith migration would affect the crater size distribution. We propose a new technique to estimate surface exposure age, focusing on the bright mottles on the large boulders. Our technique is less prone to the granular convection. These mottles are expected to be formed by impacts of mm to cm-sized interplanetary particles. Together with the well-known flux model of interplanetary dust particles (e.g., Grün, 1985 [6]), we have investigated the timescale to form such mottles before they become dark materials again by the space weathering. In this work, we used three AMICA (Asteroid Multi-band Imaging Camera) v-band images. These images were taken on 2005 November 12 during the close approach to the asteroid. As a result, we found the surface exposure timescales of these boulders are an order of 106 years. In this meeting, we will introduce our data analysis technique and evaluate the consistency among previous research for a better understanding of the evolution of this near-Earth asteroid.