• 한국항행학회논문지
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• 제27권5호
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• pp.510-518
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• 2023

본 논문에서는 지역 위성항법시스템의 항법메시지와 광역 보정정보 성능 분석을 위해 MATLAB GUI (graphic user interface) 기반으로 개발된 소프트웨어에 대해 소개한다. 본 소프트웨어는 한반도 및 주변 지역에 서비스를 제공하는 가상의 지역 위성항법시스템의 감시국 및 기준국 배치에 따른 항법메시지와 광역 보정정보의 위성 궤도/시각 관련 성능을 분석하기 위해 개발되었다. 본 소프트웨어 구동 시 항법메시지 및 광역 보정정보가 MATLAB 파일 형식으로 출력된다. 개발된 소프트웨어의 출력을 검증한 결과, 궤도 및 시계 예측 오차가 통계적 예측에 부합하며, 파라미터 피팅 오차가 cm 수준임을 확인하였다. 또한, 광역 보정정보가 측정치 차원의 오차를 81.9% 개선함을 확인하여 유효한 항법메시지 및 광역 보정정보 성능 분석이 가능함을 확인하였다.

• 한국위성정보통신학회논문지
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• 제6권1호
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• pp.37-44
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• 2011

2010년 6월 26일에 발사된 통신해양기상위성(천리안)은 Ka-대역 위성통신, 정지궤도 해양관측, 그리고 기상관측을 위한 탑재체를 가지고 있다. 정지궤도상의 위성을 효과적으로 운용하기 위해서 위성 임무운영 개념을 정립하여 이를 위성관제시스템의 개발 초기 단계부터 적용하였다. 천리안 위성의 임무운영은 일별, 주별, 월별 그리고 계절별 운영으로 구분된다. 위성의 일별운영은 임무계획, 명령계획 및 전송, 원격측정 데이터 처리 및 분석, 위성 거리측정 및 궤도결정, 위성의 궤도 및 이벤트 예측, 그리고 휠 오프로딩 파라미터 계산으로 구분된다. 위성의 주별 운영으로는 화요일에 남북방향 위치유지조정, 목요일에 동서방향 위치유지조정으로 구분된다. 월별운영으로는 위성의 온보드 오실레이터를 갱신하기 위한 비행역학 파라미터 계산과 위성으로의 전송이 수행되며 계절별 운영으로 봄과 가을에는 지구가 태양을 가리는 식에 관련된 위성운영을 수행한다. 이 논문에서는 통신해양기상위성이 발사된 후 약 3개월에 걸친 궤도 내 시험 기간 중에 이루어진 위성관제시스템의 주요 기능들에 대한 운영검증을 기술한다. 이 기간 중에 위성관제시스템의 대부분 기능이 성공적으로 검증되었으며 천리안 위성관제시스템은 위성의 설계 수명기간인 7년 또는 위성이 수명을 다하는 그 이후까지 계속 사용될 예정이다.

• 한국전산유체공학회지
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• 제19권2호
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• pp.86-92
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• 2014

In this paper, prediction of separation trajectory for Two-stage-To-Orbit space launch vehicle has been numerically simulated by using an aerodynamic database based on steady state analysis. Aerodynamic database were obtained for matrix of longitudinal and vertical positions. The steady flow simulations around the launch vehicle have been made by using a 3-D RANS flow solver based on unstructured meshes. For this purpose, a vertex-centered finite-volume method was adopted to discretize inviscid and viscous fluxes. Roe's finite difference splitting was utilized to discretize the inviscid fluxes, and the viscous fluxes were computed based on central differencing. To validate this flow solver, calculations were made for the wind-tunnel experiment model of the LGBB TSTO vehicle configuration on steady state conditions. Aerodynamic database was constructed by using flow simulations based on test matrix from the wind-tunnel experiment. ANN(Artificial Neural Network) was applied to construct interpolation function among aerodynamic variables. Separation trajectory for TSTO launch vehicle was predicted from 6-DOF equation of motion based on the interpolated function. The result of present separation trajectory calculation was compared with the trajectory using experimental database. The predicted results for the separation trajectory shows fair agreement with reference[4] solution.

• 한국항공우주학회지
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• 제38권1호
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• pp.87-93
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• 2010

과학기술위성 3호 대용량 메모리를 SEU로부터 보호하기 위해서 4비트 심볼을 이용하는 RS(10,8) 코드를 개발 하였다. 따라서 32비트 데이터에 대해서 8비트의 페리티를 추가 하였으며 1 심볼에 대해서 에러를 복구할 수 있다. 또한 우리별 3호의 결과를 이용하여 예상되는 SEU 발생률과 스크럽 주기를 계산하였다. 이 결과를 바탕으로 한국원자력 의학원에 있는 Cyclotron 양성자 가속기를 이용하여 SEU 시험을 수행 하였다.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2008년도 한국우주과학회보 제17권2호
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• pp.28.4-29
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• 2008

The aim of the test is to provide an experimental basis to validate the prediction of the FEM for high frequency jitter analysis due to reaction wheel. The principle is to measure structural transfer functions between the input disturbances at RWA base plate and the accelerations near the end tips of payload, in a configuration close to the operational model. The spacecraft shall have to be suspended, in order to be representative of on-orbit boundary conditions. The results of the test shall be compared to the output of the FEM analysis, and if needed, local upgrades of the FEM and/or margin policy shall be defined in order to guarantee a good test/FEM consistency. Test results were compared with the transfer functions of the FEM, which is globally tuned based on the results of vibration test and consequently have lower damping coefficients values than 1% in the frequency range of 60~200Hz. The damping coefficients estimated from the figures of FRF test results are different from the theoretical FEM, but the magnitude trend of FRF of the test results is somewhat similar with the analytical, it is expected that the overall jitter effect of final estimation is nearly same with the preliminary analysis result in which the damping coefficients were assumed to be 1% for all modes in FEM.

• 한국항공우주학회지
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• 제35권9호
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• pp.850-857
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• 2007

인공위성 전력계의 설계 분석은 위성 전체의 무게, 크기 및 성능을 결정하는 중요 변수로 작용한다. 특히 위성체 에너지 균형 분석의 경우 전력 시스템의 용량, 설계 제한 조건의 결정 및 위성체 운영 성공 여부를 결정할 수 있는 중요한 분석이다. 본 논문에서는 저궤도 위성 개발을 위한 새로운 에너지 균형 분석 프로그램을 소개하고 타 저궤도 위성 설계 자료를 이용한 시험 결과를 일례로 기술하였다. 시험 결과 본 논문에서 제안한 에너지 균형 분석 프로그램은 위성체 전력계의 최적 사이징 뿐 아니라 위성체 운영 기간 동안 궤도상에서의 위성체 에너지 균형 상황 예측에도 활용할 수 있음을 보였다.

• 한국가시화정보학회지
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• 제10권1호
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• pp.47-54
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• 2012

Single Stage To Orbit (SSTO) missions which require its engines to be operated at varying back pressure conditions, use engines operate at high combustion chamber pressures (more than 100bar) with moderate area ratios (AR 70~80). This ensures that the exhaust jet flows full during most part of the operational regimes by optimal expansion at each altitude. Aero-spike nozzle is a kind of altitude adaptation nozzle where requirement of high combustion chamber pressures can be avoided as the flow is adapted to the outside conditions by the virtue of the nozzle configuration. However, the thrust prediction using the conventional thrust equations remains to be a challenge as the nozzle plume shapes vary with the back pressure conditions. In the present work, the performance evaluation of a new aero-spike nozzle is being carried out. Computational studies are carried out to predict the thrust generated by the aero-spike nozzle in varying back pressure conditions which requires the unsteady pressure boundary conditions in the computational domain. Schlieren pictures are taken to validate the computational results. It is found that the flow in the aero-spike nozzle is mainly affected by the base wall pressure variation. The aerospike nozzle exhibits maximum performance in the properly expanded flow regime due to the open wake formation.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1998년도 Proceedings of International Symposium on Remote Sensing
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• pp.387-392
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• 1998

To establish a monthly data collection planning for the Ocean Scanning Multispectral Imager (OSMI), we have examined the global patterns of three impacting factors: pigment concentration, cloud cover, and sun glint. Other than satellite mission constraints (e.g., duty cycle), these three factors are considered critical for the OSMI data collection. The Nimbus-7 Coastal Zone Color Scanner (CZCS) monthly mean products and the International Satellite Cloud Climatology Project (ISCCP) monthly mean products (C2) were used for the analysis of pigment concentration and cloud cover distributions, respectively. And the monthly simulated patterns of sun glint were produced by performing the OSMI orbit prediction and the calculation of sun glint radiances at the top-of-atmosphere (TOA). Using monthly statistics (mean and/or standard deviation) of each factor in the above for a given 10$^{\circ}$ latitude by 10$^{\circ}$ longitude grid, we generated the priority map for each month. The priority maps of three factors for each month were subsequently superimposed to visualize the impact of three factors in all. The initial results illustrated that a large part of oceans in the summer hemisphere was classified into the low priority regions because of seasonal changes of clouds and sun illumination. Sensitivity tests were performed to see how cloud cover and sun glint affect the priority determined by pigment concentration distributions, and consequently to minimize their seasonal effects upon the data collection planning.

• 천문학회보
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• 제36권2호
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• pp.101.2-101.2
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• 2011

We have developed solar and space weather monitoring system for space weather users since 2007 as a project named 'Construction of Korea Space Weather Prediction Center'. In this presentation we will introduce space weather monitoring system for Geostationary Satellites and Polar Routes. These were developed for satisfying demands of space weather user groups. 'Space Weather Monitoring System for Geostationary Satellites' displays integrated space weather information on geostationary orbit such as magnetopause location, nowcast and forecast of space weather, cosmic ray count rate, number of meteors and x-ray solar flux. This system is developed for space weather customers who are managing satellite systems or using satellite information. In addition, this system provides space weather warning by SMS in which short message is delivered to users' cell phones when space weather parameters reach a critical value. 'Space Weather Monitoring System for Polar Routes' was developed for the commercial airline companies operating polar routes. This provides D-region and polar cap absorption map, aurora and radiation particle distribution, nowcast and forecast of space weather, proton flux, Kp index and so on.

• 한국소음진동공학회논문집
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• 제24권1호
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• pp.5-13
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• 2014

Number of components and payload systems installed in satellites were found to be exposed to various disturbance sources such as the reaction wheel assembly, the control moment gyro, coolers, and others. A micro-level of vibration can introduce jitter problems into an optical payload system and cause significant degradation of the image quality. Moreover, the prediction of on-orbit vibration effects on the performance of optical payloads during the development process is always important. However, analyzing interactions between subsystems and predicting the vibration level of the payloads is extremely difficult. Therefore, this paper describes the analytical and experimental approach to microvibration effects on satellite optical payload performance with integrated jitter analysis frame-work, microvibration emulator and satellite structure testbed.