• 한국항공운항학회지
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• 제15권1호
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• pp.11-17
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• 2007

One of the key elements for developing GNSS (Global Navigation Satellite Systems) is the comprehensive analysis of GNSS satellite orbit including the capabilities to generate precision navigation message. The orbit characteristics of Japan's own GNSS system, called QZSS (Quasi Zenith Satellite System) is analyzed and its navigation message, which includes orbit elements and correction terms, is investigated. QZSS-type orbit simulations were performed using a precision orbit integrator in order to analyze the effect of perturbation forces, e.g. gravity, Moon, Sun, etc., on the orbit variation. A preliminary algorithm for creating orbit element corrections was developed and its accuracy is evaluated with the simulation data.

• 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.

• Journal of Astronomy and Space Sciences
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• 제4권1호
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• pp.25-33
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• 1987

For a geostationary satellite north-south keeping maneuver must control the inclination elements. The effects on the orbit plane of maneuvers and natural perturbations may be represented by a plane plot of Wc versus, Ws, since these inclination elements represent the projection of the major axis and the inclination elements are obtained.

• Journal of Astronomy and Space Sciences
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• 제3권2호
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• pp.93-102
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• 1986

정지통신위성을 동서방향으로 궤도 조정을 하기 위해서는 평균경도와 궤도의 이심률에 관해서 동시에 조정하여야 한다. 궤도이심률의 효과는 궤도중심방향의 $e_{c}$ 과 $e_{s}$의 위상면상에서 표시되어야 한다. 평균경도와 궤도이심률에 대한 진화도 얻었다.

• 한국항행학회논문지
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• 제27권4호
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• pp.337-345
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• 2023

본 연구는 국가 초소형위성체계가 운용개념에 맞게 효과적으로 임무를 수행하기 위한 위성궤도요소 별 고려사항을 분석하고, 통상적으로 활용되고 있는 워커 기법 대비 지상반복궤적 궤도의 위성배치 기법에 대한 성능을 비교한다. 위성궤도요소 분석에서는 초소형 위성군의 고도후보군, 동결궤도를 통한 궤도 이심율 및 근지점 경도의 활용, 적절한 궤도 경사각 선정의 필요성, 동일한 지상반복궤적을 비행하기 위한 위성군 배치 규칙 등을 제안한다. 이러한 분석 결과를 기반으로 지상반복궤적 궤도의 위성군 배치는 워커 기법과 비교하여 재방문 성능 분석, 글로벌 커버리지 특성, 궤도 일관성 측면에서 우월성이 검증된다.

• Bulletin of the Korean Chemical Society
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• 제34권1호
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• pp.179-187
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• 2013

We describe newly developed software named KPACK for relativistic electronic structure computation of molecules containing heavy elements that enables the two-component ab initio calculations in Kramers restricted and unrestricted formalisms in the framework of the relativistic effective core potential (RECP). The spin-orbit coupling as relativistic effect enters into the calculation at the Hartree-Fock (HF) stage and hence, is treated in a variational manner to generate two-component molecular spinors as one-electron wavefunctions for use in the correlated methods. As correlated methods, KPACK currently provides the two-component second-order M${\o}$ller-Plesset perturbation theory (MP2), configuration interaction (CI) and complete-active-space self-consistent field (CASSCF) methods. Test calculations were performed for the ground states of group-14 elements, for which the spin-orbit coupling greatly influences the determination of term symbols. A categorization of three procedures is suggested for the two-component methods on the basis of spin-orbit coupling manifested in the HF level.

• International Journal of Aerospace System Engineering
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• 제7권2호
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• pp.6-12
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• 2020

The precise prediction of future position of satellite depends on the accurate determination of orbit, which is also helpful in performing orbit maneuvers and trajectory correction maneuvers. For estimating the orbit of satellite many methods are being used. Some of the conventional methods are based on (i) Differential Correction (DC) (ii) Extended Kalman Filter (EKF). In this paper, Differential Evolution (DE) is used to determine the orbit. Orbit Determination using DC and EKF requires some initial guess of the state vector to initiate the algorithm, whereas DE does not require an initial guess since a wide range of bounds for the design unknown variables (orbital elements) is sufficient. This technique is uniformly valid for all orbits viz. circular, elliptic or hyperbolic. Simulated observations have been used to demonstrate the performance of the method. The observations are generated by including random noise. The simulation model that generates the observations includes the perturbation due to non-spherical earth up to second zonal harmonic term.

• Journal of Astronomy and Space Sciences
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• 제6권2호
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• pp.91-100
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• 1989

정지 위성 궤도의 평균 궤도 요소를 비 특이점 궤도 요소 항으로 연구하였다. 실제 위성의 위치는 평균 궤도로부터 단주기 섭동 만큼 위성 위치가 진동하는데, 그 진동의 진폭은 1800m 이하이다. $e_c$ 와 $e_s$의 평균값도 얻었다.

• 한국항공우주학회지
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• 제31권10호
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• pp.40-50
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• 2003

저고도, 태양동기궤도인 아리랑 1호의 최초 임무운영 목표였던 3년 동안 관측된 궤도 변화를 분석하였다. 초기운영기간 동안 최적화된 궤도를 획득하기 위해 총 4회의 궤도조정이 있었으며, 총 8회의 안전모드가 발생하였다. 예상치 않은 안전모드 발생과 임무기간 동안 최고조에 달했던 태양활동이 궤도변화에 미치는 영향을 분석하였고, 초기 궤도조정 완료 직후 임무운영 기간에 대해 예측되었던 장기 궤도예측 결과와 궤도결정을 통해 실측된 궤도와의 차이를 분석하였다. 최적화된 궤도에서부터 운영된 3년의 임무기간 동안 고도를 제외한 나머지 궤도요소들은 설계된 임무궤도 범위 내에서 변화하였고, 태양동기궤도 특성을 유지하였음을 확인하였다.

• Journal of Astronomy and Space Sciences
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• 제31권3호
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• pp.199-204
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• 2014

This paper intends to highlight the effect of the third-body in an inclined orbit on a spacecraft orbiting the primary mass. To achieve this goal, a new origin of coordinate is introduced in the primary and the X-axis toward the node of the spacecraft. The disturbing function is expanded up to the second order using Legendre polynomials. A double-averaged analytical model is exploited to produce the evolutions of mean orbital elements as smooth curves.