• 제목/요약/키워드: Orbital Element

검색결과 40건 처리시간 0.026초

Spin-Orbit Density Functional Theory Calculations for TlAt with Relativistic Effective Core Potentials

  • Choi, Yoon-Jeong;Bae, Cheol-Beom;Lee, Yoon-Sup;Lee, Sang-San
    • Bulletin of the Korean Chemical Society
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    • 제24권6호
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    • pp.728-730
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    • 2003
  • Bond lengths, harmonic vibrational frequencies and dissociation energies of TlAt are calculated at ab initio molecular orbital and density functional theory using effective spin-orbit operator and relativistic effective core potentials. Spin-orbit effects estimated from density functional theory are in good agreement with those from ab initio calculations, implying that density functional theory with effective core potentials can be an efficient and reliable methods for spin-orbit interactions. The estimated $R_e$, $ω_e$ and $D_e$ values are 2.937 ${\AA}$, 120 $cm^{-1}$, 1.96 eV for TlAt. Spin-orbit effects generally cause the bond contraction in Group 13 elements and the bond elongation in the Group 17 elements, and spin-orbit effects on Re of TlAt are almost cancelled out. The spinorbit effects on $D_e$ of TlAt are roughly the sum of spin-orbit effects on $D_e$ of the corresponding element hydrides. Electron correlations and spin-orbit effects are almost additive in the TlAt molecule.

Formulas of Position and Velocity Perturbation for Hyperbolic Orbit and Its Application to Flyby Anomaly

  • Kim, Young-Kwang;Park, Sang-Young
    • 한국우주과학회:학술대회논문집(한국우주과학회보)
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    • 한국우주과학회 2011년도 한국우주과학회보 제20권1호
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    • pp.26.2-26.2
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    • 2011
  • Flyby anomaly (unexpected energy increase during Earth Gravity Assists) indicates existence of an unknown non-conservative perturbation which affects hyperbolic trajectories. This presentation focuses on first order position and velocity perturbation formulas derived in terms of classical orbital element variations for hyperbolic orbit. By using both the perturbation formulas and numerical approach, we analyze effects of hypothetical acceleration models proposed by Hasse (2009), Lewis (2009), Gerrad and Sumner (2008), and Busack (2007). Based on analysis of perturbation effect on low earth orbit, we find that typical position perturbation is about 10m which is much larger than current orbit determination accuracy. From this, we deduce that anomalous acceleration only affects hyperbolic orbit or behaves differently in bound orbit. On the other hand, based on analysis of perturbation effects on hyperbolic trajectories, we find that position and velocity perturbations are highly different from acceleration models, and all of proposed models fail to explain observed range and Doppler data. Thus, it can be concluded that not only energy variations but also kinematics gives us crucial clues on the flyby anomaly, and kinematical characteristic should be considered in modeling flyby anomaly.

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Physical properties of Maria asteroid family

  • 김명진;최영준;문홍규;;변용익
    • 천문학회보
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    • 제37권1호
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    • pp.101.2-101.2
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    • 2012
  • An asteroid family is a population of asteroids in the proper orbital element space (a, e, i), considered to have been produced by a disruption of a large parent body presumably through a catastrophic collision. Asteroid families offer unique opportunities to reconstruct and characterize the break-up history of airless bodies in the main-belt. The Maria family is a typical old population (~3${\pm}$1 Gyr) of asteroids that have undergone significant collisional and dynamical evolution in the history of the inner Solar System; it is also believed to be one of the candidate source regions for giant S-type near-earth asteroids (NEAs). However, to date, physical characteristics of this family members such as rotational periods have been known only for 61 of the larger asteroids among 3,230 objects, which accounts for less than 2 percent of the family. In this presentation, we provide some preliminary results of our recent study: out of more than dozen of the family members, lightcurves for eight objects have been obtained for the first time. We plan to increase the number of target objects, and investigate evidences for the Yarkovsky/YORP effect on Maria family based on our observations.

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보현산 천문대 소행성 관측 연구 (KEEP-North : Kirkwood Excitation and Exile Patrol of the Northern Sky)

  • Kim, Myung-Jin;Choi, Young-Jun;Moon, Hong-Kyu
    • 천문학회보
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    • 제41권1호
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    • pp.61.3-62
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    • 2016
  • An asteroid family is a group of asteroidal objects in the proper orbital element space (a, e, and i), considered to have been produced by a disruption of a large parent body through a catastrophic collision. Family members usually have similar surface properties such as spectral taxonomy types, colors, and visible geometric albedo with a same dynamical age. Therefore an asteroid family could be called as a natural Solar System laboratory and is also regarded as a powerful tool to investigate space weathering and non-gravitational phenomena such as the Yarkovsky/YORP effects. We carry out time series photometric observations for a number of asteroid families to obtain their physical properties, including sizes, shapes, rotational periods, spin axes, colors, and H-G parameters based on nearly round-the-clock observations, using several 0.5-2 meter class telescopes in the Northern hemisphere, including BOAO 1.8 m, LOAO 1.0 m, SOAO 0.6 m facilities in KASI, McDonald Observatory 2.1 m instrument, NARIT 2.4 m and TUG 1.0 m telescopes. This study is expected to find, for the first time, some important clues on the collisional history in our Solar System and the mechanisms where the family members are being transported from the resonance regions in the Main-belt to the near Earth space.

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스핀코팅법에 의해 제조되어진 Yttrium이 도핑된 ZnO 막의 특성 (Characterization of Yttrium Doped Zinc Oxide Thin Films Fabricated by Spin-coating Method)

  • 김현주;이동윤;송재성
    • 한국전기전자재료학회논문지
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    • 제19권5호
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    • pp.457-460
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    • 2006
  • Y doped zinc oxide (YZO) thin films were deposited on F doped $SnO_2$ (FTO) glass substrate by sol-gel method using the spin-coating system. A homogeneous and stable solution was prepared by dissolving acetate in the solution added diethanolamine as sol-gel stabilizer. YZO films were obtained after preheated on the hot-plate for 5minute before each coating; the number of coating was 3 times. After the coating of last step, annealing of YZO films performed at $450^{\circ}C$ for 30 minute. In order to confirming of a ultraviolet ray interruption and down-conversion effects, optical properties of YZO films, transmission spectrum and fluorescent spectrum were used. Also, for understanding the obtained results by experiment, the elestronic state of YZO was calculated using the density functional theory The results obtained by experiment were compared with calculated structure. The detail of electronic structure was obtained by the discrete variational Xa (DV-Xa) method, which is a sort of molecular orbital full potential method. The density of state and energy levels of dopant element were shown and discussed in association with optical properties.

Space Surveillance Radar Observation Analysis: One-Year Tracking and Orbit Determination Results of KITSAT-1, "우리별 1호"

  • Choi, Jin;Jo, Jung Hyun;Choi, Eun-Jung;Yu, Jiwoong;Choi, Byung-Kyu;Kim, Myung-Jin;Yim, Hong-Suh;Roh, Dong-Goo;Kim, Sooyoung;Park, Jang-Hyun;Cho, Sungki
    • Journal of Astronomy and Space Sciences
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    • 제37권2호
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    • pp.105-115
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    • 2020
  • The Korean Institute of Technology Satellite (KITSAT-1) is the first satellite developed by the Satellite Technology Research Center and the University of Surrey. KITSAT-1 is orbiting the Earth's orbit as space debris with a 1,320 km altitude after the planned mission. Due to its relatively small size and altitude, tracking the KITSAT-1 was a difficult task. In this research, we analyzed the tracking results of KITSAT-1 for one year using the Midland Space Radar (MSR) in Texas and the Poker Flat Incoherent Scatter Radar (PFISR) in Alaska operated by LeoLabs, Inc. The tracking results were analyzed on a weekly basis for MSR and PFISR. The observation was conducted by using both stations at an average frequency of 10 times per week. The overall corrected range measurements for MSR and PFISR by LeoLabs were under 50 m and 25 m, respectively. The ionospheric delay, the dominant error source, was confirmed with the International Reference of Ionosphere-16 model and Global Navigation Satellite System data. The weekly basis orbit determination results were compared with two-line element data. The comparison results were used to confirm the orbital consistency of the estimated orbits.

Optical Monitoring Strategy for Avoiding Collisions of GEO Satellites with Close Approaching IGSO Objects

  • Choi, Jin;Jo, Jung Hyun;Yim, Hong-Suh;Choi, Young-Jun;Park, Maru;Park, Sun-Youp;Bae, Young-Ho;Roh, Dong-Goo;Cho, Sungki;Park, Young-Sik;Jang, Hyun-Jung;Kim, Ji-Hye;Park, Jang-Hyun
    • Journal of Astronomy and Space Sciences
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    • 제32권4호
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    • pp.411-417
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    • 2015
  • Several optical monitoring strategies by a ground-based telescope to protect a Geostationary Earth Orbit (GEO) satellite from collisions with close approaching objects were investigated. Geostationary Transfer Orbit (GTO) objects, Inclined GeoSynchronous Orbit (IGSO) objects, and drifted GEO objects forced by natural perturbations are hazardous to operational GEO satellites regarding issues related to close approaches. The status of these objects was analyzed on the basis of their orbital characteristics in Two-Line Element (TLE) data from the Joint Space Operation Center (JSpOC). We confirmed the conjunction probability with all catalogued objects for the domestic operational GEO satellite, Communication, Ocean and Meteorological Satellite (COMS) using the Conjunction Analysis Tools by Analytical Graphics, Inc (AGI). The longitudinal drift rates of GeoSynchronous Orbit (GSO) objects were calculated, with an analytic method and they were confirmed using the Systems Tool Kit by AGI. The required monitoring area was determined from the expected drift duration and inclination of the simulated target. The optical monitoring strategy for the target area was analyzed through the orbit determination accuracy. For this purpose, the close approach of Russian satellite Raduga 1-7 to Korean COMS in 2011 was selected.

Operational Report of the Mission Analysis and Planning System for the KOMPSAT-I

  • Lee, Byoung-Sun;Lee, Jeong-Sook;Kim, Jae-Hoon;Lee, Seong-Pal;Kim, Hae-Dong;Kim, Eun-Kyou;Park, Hae-Jin
    • 한국우주과학회:학술대회논문집(한국우주과학회보)
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    • 한국우주과학회 2003년도 한국우주과학회보 제12권2호
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    • pp.46-46
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    • 2003
  • Since its launching on 21 December 1999, the KOrea Multi-Purpose SATellite-Ⅰ (KOMPSAT-Ⅰ) has been successfully operated by the Mission Control Element (MCE), which was developed by the Electronics and Telecommunications Research Institute (ETRI). Most of the major functions of the MCE have been successfully demonstrated and verified during the three years of the mission life of the satellite. The Mission Analysis and Planning Subsystem (MAPS), which is one of the four subsystems in the MCE, played a key role in the Launch and Early Orbit Phase (LEOP) operations as well as the on-orbit mission operations. This paper presents the operational performances of the various functions in MAPS. We show the performance and analysis of orbit determinations using ground-based tracking data and GPS navigation solutions. We present four instances of the orbit maneuvers that guided the spacecraft from injection orbit into the nominal on-orbit. We include the ground-based attitude determination using telemetry data and the attitude maneuvers for imaging mission. The event prediction, mission scheduling, and command planning functions in MAPS subsequently generate the spacecraft mission operations and command plan. The fuel accounting and the realtime ground track display also support the spacecraft mission operations. We also present the orbital evolutions during the three years of the mission life of the KOMPSAT-Ⅰ.

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우주파편 충돌분석을 위한 CSM 궤도데이터 분석 (An Analysis of CSM orbit for Conjunction Assessment of Space Debris)

  • 최수진;김해동;정옥철
    • 한국항공우주학회지
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    • 제41권2호
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    • pp.164-171
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    • 2013
  • 우주파편은 1957년 인류가 우주에 위성을 보내기 시작하면서 그 숫자가 급격하게 증가하고 있으며, 현재 미합동우주전략사령부(JSpOC, Joint Space Operations Center)에 의하면 지름 10cm 이상의 우주파편이 22,000개 이상이라고 알려지고 있다. 최근에는 중국이 자국의 위성을 미사일로 요격시킨 사건과 Iridium 33 및 Cosmos 2251 위성이 우주상공에서 서로 충돌한 사건이 발생함에 따라 아리랑 2호가 운영 중인 저궤도의 우주환경이 급격히 악화되고 있다. 미합동우주전략사령부는 15,000개 이상의 우주파편의 궤도정보를 이용하여 운영위성과의 충돌분석을 수행하고 있으며, 충돌 위험이 발생할 경우 해당 위성의 운영자에게 CSM(Conjunction Summary Message)이란 형식의 메시지를 제공하여 충돌분석 시 활용할 수 있도록 지원하고 있다. 본 논문은 JSpOC에서 제공하는 CSM의 아리랑2호 궤도데이터와 항우연이 관리하는 아리랑 2호의 정밀궤도 데이터와 비교하였으며, 아리랑 2호와 우주파편과의 충돌분석 결과를 도시하였다.

Pd(111) 박막의 자성: 제일원리계산 (Magnetism of Pd(111) Thin Films: A First-principles Calculation)

  • 홍순철
    • 한국자기학회지
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    • 제26권1호
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    • pp.1-6
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    • 2016
  • Pd은 단일 원소 금속 중에서 자기 감수율이 가장 크고 외부 환경에 따라 강자성 특성을 보이기도 한다. 본 논문은 자성 연구에 가장 적합한 FLAPW 방법을 사용하여 5-ML과 9-ML Pd(111) 박막의 자성을 계산하였다. 전자간 교환-상관 상호작용을 고려하기 위해 LDA와 GGA를 도입하여 두 계산 결과를 비교하였다. LDA 계산은 덩치 Pd이 상자성 상태가 바닥 상태임을 예측하여 실험과 일치하는 반면, GGA 계산은 덩치 Pd이 강자성을 갖는 것으로 잘못 예측하여 Pd 자성에 대해서는 LDA 계산이 더 신뢰할 수 있음을 알았다. 5-ML Pd(111) 박막에 대한 LDA 계산 결과에 의하면 상자성 상태가 바닥인 덩치 Pd과는 다르게 강자성 상태가 더 안정적이었다. 박막의 중앙에 위치한 Pd이 가장 큰 자기모멘트($0.273{\mu}_B$)를 가지며 중앙 Pd 층의 |m| = 1 상태가 덩치의 그것과 큰 차이가 있어 5-ML Pd(111) 박막의 강자성을 유발하는 데 주요 역할을 함을 알 수 있었다. 9-ML Pd(111) 박막은 상자성 상태가 강자성 상태에 비해 안정하였으나 두 상태 사이의 총에너지 차이가 거의 없고 유한한 자기모멘트를 안정적으로 가지는 것으로 계산되어 강자성 상태가 준 안정적임을 보였다.