• 한국항공우주학회지
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• 제42권10호
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• pp.823-832
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• 2014

변위 비케플러 궤도란 질량중심이 궤도면에 대하여 변위를 갖는 궤도인데, 일반적인 궤도에 비해 다양한 임무를 수행할 수 있다는 장점이 있다. 비케플러 궤도를 유지하기 위해서는 지속적인 추력이 필요한데, 태양돛 우주선은 연료 소모 없이 지속적으로 추력을 얻을 수 있기 때문에 비케플러 궤도 운용에 적합하다. 본 논문에서는 소모성 추진제와 태양돛에 모두 적용할 수 있는 비케플러 궤도 이론을 소개하고, 태양돛 우주선에 적용시 차이점을 분석하였다. 비케플러 궤도를 4가지 유형으로 분류하고 궤도 유지를 위한 요구가속도를 계산하였다. 각 유형별 궤도안정성 식을 분석하고 시뮬레이션을 통해 검증하였다. 불안정 영역에서 궤도를 제어하기 위해 실시간 LQR을 적용한 제어기법을 개발하여 이에 대한 시뮬레이션을 수행하였다.

• 한국지구과학회지
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• 제33권1호
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• pp.11-31
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• 2012

카울라에 의해 완성되었던 인공위성궤도이론과 케플러의 법칙을 다시 다루었다. 카울라의 원문에서는 생략되었던 부분을 포함한 모든 수식유도과정을 상세히 기술하였다. 특히 15개의 독립적인 라그랑지 괄호들을 계산하는 데에 변환행렬의 직교성을 사용하여, 간결성과 명확성을 이루었다. 여러 중간단계에서 중요한 물리적인 개념들에 대한 설명도 추가하였다. 카울라의 개념적 오류 한 개를 정정하였다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
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• pp.505-510
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• 2006

SVLBI (Space Very Long Baseline Interferometry) has some important potential applications in geodesy and geodynamics, for which one of the most difficult tasks is to precisely determine the orbit of SVLBI satellite. This paper studies several technologies which possibly will be able to determine the orbit of space VLBI satellite. And then, according to the sorts and characteristicsof satellite and the requirements for geodetic study and the geometry of GNSS (GPS, GALILEO) satellite to track the space VLBI satellite, the six Keplerian elements of SVLBI satellite (TEST-SVLBI) are determined. A program is designed to analyze the coverage area of the space of different heights by the stations of the network, with which the tracking network of TEST-SVLBI is designed. The efficiency of tracking TEST-SVLBI by the network is studied, and the results are presented.

• International Journal of Aeronautical and Space Sciences
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• 제16권1호
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• pp.77-88
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• 2015

The dynamics of relative motion in a perturbed orbital environment are exploited based on Gauss' and Cowell's variational equations. The inertial coordinate frame and relative coordinate frame (Hill frame) are used, and a linear high fidelity model is developed to describe the relative motion. This model takes into account the primary gravitational and atmospheric drag perturbations. Then, this model is used in the design of a navigation, guidance, and control system of a chaser vehicle to approach towards and to depart from a target vehicle in proximity operations. Relative navigation uses an extended Kalman filter based on this relative model to estimate the relative position/velocity of the chaser vehicle with respect to the target vehicle. This filter uses the range and angle measurements of the target relative to the chaser from a simulated LIDAR system. The corresponding measurement models, process noise matrix, and other filter parameters are provided. Numerical simulations are performed to assess the precision of this model with respect to the full nonlinear model. The analyses include the navigation errors and trajectory dispersions.

• 천문학회보
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• 제43권2호
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• pp.39.1-39.1
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• 2018

We present our observational attempts to precisely measure the central mass of a proto-brown dwarf candidate, L328-IRS, in order to investigate whether L328-IRS is in the substellar mass regime. Observations were made for the central region of L328-IRS with the dust continuum and CO isotopologue line emission at ALMA band 6, discovering the detailed outflow activities and a deconvolved disk structure of a size of ${\sim}87AU{\times}{\sim}37AU$. We investigated the rotational velocities as a function of the disk radius, finding that its motions between 130 AU and 60 AU are partially fitted with a Keplerian orbit by a stellar object of ${\sim}0.30M_{\odot}$, while the motions within 60 AU do not follow any Keplerian orbit at all. This makes it difficult to lead a reliable estimation of the mass of L328-IRS. Nonetheless, our ALMA observations were useful enough to well constrain the inclination angle of the outflow cavity of L328-IRS as ${\sim}66^{\circ}$ degree, enabling us to better determine the mass accretion rate of ${\sim}8.9{\times}10^{-7}M_{\odot}yr-1$.From assumptions that the internal luminosity of L328-IRS is mostly due to this mass accretion process in the disk, or that L328-IRS has mostly accumulated the mass through this constant accretion rate during its outflow activity, its mass was estimated to be ${\sim}0.012-0.023M_{\odot}$, suggesting L328-IRS to be a substellar object. However, we leave our identification of L328-IRS as a proto-brown dwarf to be tentative because of various uncertainties especially regarding the mass accretion rate.

• Journal of Astronomy and Space Sciences
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• 제28권1호
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• pp.37-54
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• 2011

Two semi-analytic solutions for a perturbed two-body problem known as Lagrange planetary equations (LPE) were compared to a numerical integration of the equation of motion with same perturbation force. To avoid the critical conditions inherited from the configuration of LPE, non-singular orbital elements (EOE) had been introduced. In this study, two types of orbital elements, classical Keplerian orbital elements (COE) and EOE were used for the solution of the LPE. The effectiveness of EOE and the discrepancy between EOE and COE were investigated by using several near critical conditions. The near one revolution, one day, and seven days evolutions of each orbital element described in LPE with COE and EOE were analyzed by comparing it with the directly converted orbital elements from the numerically integrated state vector in Cartesian coordinate. As a result, LPE with EOE has an advantage in long term calculation over LPE with COE in case of relatively small eccentricity.

• 한국측량학회지
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• 제27권2호
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• pp.119-127
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• 2009

다양한 차세대 위성항법시스템들이 개발되고 있지만, 현재 사용자가 측위에 이용할 수 있는 위성항법시스템은 GPS와 GLONASS 뿐이다. 이 연구에서는 GLONASS의 궤도력 중에서 알마낙을 이용하여 위성궤도를 예측하고 예측궤도의 정확도를 평가하였다. 예측궤도를 생성하기 위하여 알마낙 파일에 포함되어 있는 케플러 궤도요소와 궤도방정식을 이용하였으며, 그 결과는 정밀궤도력과의 좌표 비교를 통하여 정확도를 검증하였다. 그 결과, 7일 동안 예측한 위성궤도의 3차원 최대오차는 155.4km로 나타났으며, RMS 오차는 56.3km로 나타났다. 또한 실제관측 결과와의 비교를 통해 궤도오차가 위성의 가시성을 분석하는데 무리가 없는 수준임을 확인하였다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.1162-1164
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• 2003

The methods of the geometric reconstruction and sensor calibration of satellite linear pushbroom images are investigated. The model of the sensor used is based on the SPOT model that is developed by Kraiky. The satellite trajectory is a Keplerian trajectory in the approximation. Four orbit parameters, longitude of the ascending node(${\omega}$), inclination of the orbit plan(I), latitude argument of the satellite(W) and distance between earth center and satellite, are used for the camera modeling. Time-dependent orbit parameters are expressed by quadratic polynomials. SPOT-5 images have been used for validation tests. The results are that the RMSE acquired from 20 GCPs is 1.763m and the RMSE of 5 checking points 2.470m. Because the ground resolution of SPOT-5 is 2.5m, the result obtained in this study has a good accuracy. It demonstrates that the sensor model developed by this study can be used to reconstruct the geometry of satellite image using pushbroom camera.

• Journal of Astronomy and Space Sciences
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• 제20권4호
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• pp.319-326
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• 2003

The motion of each satellite in a tethered satellite system is non-Keplerian in the Earth's gravitational field. In this paper, the tether perturbation force is formulated and compared with the perturbation force due to the Earth's oblateness. Also, the center of mass motion of the tethered satellite system is analyzed. The tether perturbing force on the one of satellites in a tethered satellite system is much bigger than the Earth's oblateness perturbation. The two-body motion approximation of the center of mass is acceptable to describe the motion of the system, when the libration is small.

• 한국항공우주학회지
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• 제50권10호
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• pp.709-716
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• 2022

본 논문에서는 IUS (Inertial Upper Stage)에 사용된 Gamma 유도 방식을 상단이 고체모터로 구성된 위성발사체 유도를 위해 적용해 보았다. 알고리듬의 수렴성 및 고체모터의 속도 오차 보상을 위해 RCS(Reaction Control System)가 최상단 연소 종료 후 작동하는 것으로 두었다. 알고리듬 계산 과정 중 최종 궤도 투입 오차 예측을 위한 적분과정을 Keplerian 궤적으로 단순화함으로써 수치 적분과정이 없도록 알고리듬을 구성하였다. 유도 알고리듬 평가를 위해 비공칭 비행 조건에 대한 3-DOF 컴퓨터 시뮬레이션을 수행해 주어진 상단 유도 방식은 개루프 명령을 적용한 경우 대비 궤도 투입 오차를 줄일 수 있음을 보였다.