• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.45.4-45.4
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• 2009

저궤도 위성에 사용된 반작용휠을 이용한 자세제어 로직의 임무기간 동안의 성능 변화 양상을 분석하였다. 분석에 사용한 저궤도 위성은 임무기간 3년에 고도 685km의 태양 동기 궤도이며 자세제어 센서로 별 추적기 2개를 사용하였고, 구동기로 반작용 휠 4개를 사용하였다. 시간에 따른 성능 감소 경향성을 분석하기 위해 2006년 8월부터 2009년 9월까지 원격측정 데이터를 분석하여 반작용휠을 이용한 자세제어기의 기동시의 기동각에 따른 수렴시간 분석을 수행하였다. 임무 초기에 수행한 기동 수렴시각과 임무 종료 시점 근처에서 수행한 기동 수렴 시각을 비교한 결과 여전히 초기와 유사한 성능을 보이고 있음을 확인하였다.

• Journal of the Korean Society for Railway
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• v.13 no.6
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• pp.601-607
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• 2010

The objective of this paper is to propose a fast and easy Binary Artificial Bee Colony (BABC) heuristic algorithm to optimize NP-hard scheduling problem of railway track maintenance considering real conditions. The optimal or best solutions can be found using proposed BABC within very short or user specified computation time. We can greatly maximize the objective value using this proposed method in 30, 60, 100 and 200 work size railway track maintenance scheduling problems for experiment and analysis.

• Journal of Astronomy and Space Sciences
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• v.22 no.4
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• pp.451-462
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• 2005

Optimal Trajectory Correction Maneuver (TCM) design algorithm has been developed using the B-plane targeting method for future Korean Mars missions. For every-mission phase, trajectory informations can also be obtained using this developed algorithms which are essential to design optimal TCM strategy. The information were computed under minimum requiring perturbations to design Mars missions. Spacecraft can not be reached at designed aim point because of unexpected trajectory errors, caused by many perturbations and errors due to operating impulsive maneuvers during the cruising phase of missions. To maintain spacecraft's appropriate trajectory and deliver it to the designed aim point, B-plane targeting techniques are needed. A software NPSOL is used to solve this optimization problem, with the performance index of minimizing total amount of TCM's magnitude. And also executing time of maneuvers on be controlled for the user defined maneuver number $(1\~5)$ of TCMs. The constraints, the Mars arrival B-plane boundary conditions, are formulated for the problem. Results of this work show the ability to design and analyze overall Mars missions, from the Earth launch phase to Mars arrival phase including capture orbit status for future Korean Mars missions

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.1
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• pp.39-47
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• 2005

In this paper, a method of station keeping strategy using relative orbital motion and numerical optimization technique is presented for geostationary spacecraft. Relative position vector with respect to an ideal geostationary orbit is generated using high precision orbit propagation, and compressed in terms of polynomial and trigonometric function. Then this relative orbit model is combined with optimization scheme to propose a very efficient and flexible method of station keeping planning. Proper selection of objective and constraint functions for optimization can yield a variety of station keeping methods improved over the classical ones. Results from the nonlinear simulation have been shown to support such concept.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.11
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• pp.1112-1120
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• 2009

In this paper, the authors introduced a new approach to find the target orbits of each satellite in order to establish a temporary reconnaissance constellation mission to minimize the average revisit time (ART) while satisfying the constraint on fuel limit. Two distinct problems are dealt with: the first is to reconnoiter the local area with discriminating fuel constraint the second is to reconnoiter ground moving target with same fuel constraint. A preliminary effort in applying a genetic algorithm to those problems has also been demonstrated through simulation study. The results show that current ARTs of each mission are reduced by 41% and 42%, respectively, by relocating the orbit of each satellite. Naturally, the final result may depend on satellite orbits, sensor characteristics, allowable fuel cost, thruster capability, and maneuver strategies.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.10
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• pp.51-59
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• 2005

In this paper, results of a multiple spacecraft formation-keeping control using the orbital relative motion and optimization technique are presented. To analyze and predict the relative motion between the formation-flying satellites, a closed-form orbit propagator obtained using the method of ephemeris compression is used. This closed-form orbit propagator is combined with optimization technique to plan a series of impulsive maneuvers, which maintain the formation configuration within the specified limit. As an example, this method is applied to the problem of maintaining the projected circular formation geometry and results from nonlinear simulation are presented.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.108-116
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• 2009

This paper considers the trajectory design problem for a lunar orbiter when launched by KSLV-II. KSLV-II puts its kick motor stage and lunar orbiter into a low earth orbit, and then the kick motor stage performed the translunar injection. To simulate more realistic situations, TLI (Trans-Lunar Injection) and LOI (Lunar Orbit Injection) maneuvers are modeled as finite burns. The feasibility of the lunar mission by KSLV-II are confirmed by the numerical results that show the reasonable required-velocity and propellant usage.

• Journal of the Korean Society for Railway
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• v.8 no.2
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• pp.111-115
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• 2005

The Study provides the technical background and calculation method f3r the long wave track defect. On high speed railway, It is necessary to manage the long wave band up to 80m track defect fur improving a riding quality. For this reason, Track recording methods for highspeed railway are used 10m and 30m recording bases, these are covered middle wave band and long wave band successfully. Extended base recording data is calculated by geometrical model and this data provides a good result for KTX riding index.

• Journal of the Korean Society for Railway
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• v.7 no.4
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• pp.291-295
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• 2004

The Track geometry measuring on High-speed railway is the most important subject for the track construction and track maintenance work. Also the measuring accuracy is so significant part because it provides principle data for the maintenance plan and the assesment of working quality and can control the train speed limitation. From this point of view, it is very important to verify for the track recording coach(EM120) in KNR. According to the result of spectrum analysis, the noise near 1m waveband was found on the track recording data from EM120. So, New filter has been applied to remove the noise form track recording data. and it makes possible to acquire resembling result to real track geometry.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.46.1-46.1
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• 2019

우리나라 최초의 우주탐사 사업인 달 탐사선(KPLO) 개발 사업에는 국내에서 개발하는 과학 탑재체 3기, 기술 검증탑재체 1기, 고해상도 카메라 1기, 국제협력의 일환으로 NASA의 과학 탑재체 1기도 함께 개발되고 있다. KPLO와 이들 탑재체의 운영을 수행하게 될 KPLO 심우주 지상시스템은 달 탐사선 운영에 필요한 궤도, 임무계획 등의 정보를 생성하고, KPLO의 기동명령과 상태정보를 송, 수신하는 역할을 주요 임무로 수행한다. 또한 이들 정보를 기반으로 궤도임무를 수행하고 있는 KPLO의 임무운영 상태를 시각화하여 운영자로 하여금 KPLO 운영을 용이하게 하고, 공공에게 이를 제공하는 역할도 함께 수행한다. KPLO 심우주 지상시스템은 AGI사의 STK와 NASA/JPL에서 개발한 Cosmographia를 활용하여 각각 특성에 맞는 KPLO 운영 시각화 정보를 제공할 것이다. 본 발표에서는 Cosmographia의 작동 및 활용 개념을 설명하고, KPLO의 가상 임무를 적용한 SPICE Kernels을 활용하여 고해상도 카메라인 LUTI의 지향, 달 중심 표준좌표를 적용한 KPLO의 궤도 등을 시각화 시연을 한다. 또한 고해상도 달 표면 영상 적용, 심우주 네트워크 안테나의 위치 정보표출 등 Cosmographia에서 기본적으로 제공하던 시각화 정보를 개선한 내용에 대해서도 함께 시연한다.