• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.140.1-140.1
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• 2011

한국우주전파관측망(KVN)은 2009년 후반기부터 단일경으로 연구관측을 계속하면서 이제 22/43 GHz 대 VLBI로서의 연구관측을 앞두고 있다. 여기에서는 KVN의 중요한 연구분야의 하나인 점근적색거성에서 전행성상성운에 이르기까지 진화과정에 대한 KVN 단일 경 관측연구룰 소개하고 앞으로의 VLBI 연구방향을 소개하고자 한다. 단일경 연구에는 SiO 및 H2O 메이저선 동시관측에 의한 점근적색거성과 후점근적색거성 등에 대한 서베이 및 상대적으로 강한 메이저선 강도를 보이는 각 단계별 관심 천체에 대한 시간 모니터링 관측 결과를 소개한다.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.194.1-194.1
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• 2012

우주비행체의 내부 장치 고장 혹은 외부 환경에 의한 고장이 발생할 경우를 대비하여 가상 모의 시뮬레이터를 이용한 고장 대응 훈련이 요구된다. 시뮬레이터 개발 초기에 이러한 고장 발생 메커니즘을 설계에 반영하지 않는 경우 교관이 작성한 고장 시나리오에 의한 유기적 고장 발생 및 고장 전파 기능을 납품 후 추가 요구하기는 용이하지 않다. 본 논문에서는 사용자가 시뮬레이터를 이용하여 의도하는 고장을 의미있는 시각(Epoch)에 주입하기 위한 고장 발생 메커니즘 구조를 설명한다. 또한 천리안위성 시뮬레이터 소프트웨어의 고장 발생 예제를 통해 고장 감지, 고장 복구, 관제원의 대응 방법 등을 설명한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2018.06a
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• pp.123-124
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• 2018

본 논문에서는 HEVC 국제표준으로 압축된 비디오에서 움직임 물체를 추적하는 방법을 제안한다. 제안하는 방법은 HEVC 비트스트림의 대부분을 차지하는 인터 프레임의 움직임 벡터 정보를 입력 데이터로 사용하는 ST-MRF(Spatio-Temporal-Markov Random Field) 모델을 기반으로 하며, ST-MRF 모델에서 발생할 수 있는 오차전파로 점진적으로 객체를 부정확하게 추적하는 것을 HEVC GOP(Group of Picture)마다 삽입되는 인트라 프레임만을 복호화 하여 픽셀 정보를 입력으로 하는 YOLO 모델과 융합시켜 보정함으로써 추적하던 객체를 잃지 않고 강건하게 추적하는 방법을 제안한다.

• Journal of Satellite, Information and Communications
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• v.7 no.3
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• pp.78-85
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• 2012

This paper takes precautions proposals against prospective disasters from the space weather maximum in 2013. The space weather maximum could wreak havoc in this world. A geomagnetic space storm sparked by a solar eruption like the one that flared toward earth is bound to strike again and could wreak havoc across the modern world. Despite of the fact that not only researches by colleges and institutions current researches have been focusing on warning systems of space communication and the earth network systems, but also management and control systems are not situated for the space weather blasters. The purpose of the study is that the damage reduces methods implementation on the ultimate space weather communication systems by above lists proposed type analysis. In result, the implementation of the communication disaster management systems deals with the smart IT converged GIS analysis on the flare, solar proton event, geomagnetic storm to the effects of the geomagneticsphere, ionosphere and troposphere from solar maximum. This research can provide affective methods for the saving lives and property protections that implementation of the disaster prediction and disaster prevention systems adapts smart IT systems and converged high tech information systems using decision making support systems of the GIS methodology.

• Aerospace Engineering and Technology
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• v.4 no.2
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• pp.163-170
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• 2005

According to the KSLV program of KARI, it is planed to develop various launch vehicle and satellite 10 years hereafter. Large-scale test facilities, such as ReTF and PTA-II, are needed to fulfill this launch vehicle/satellite development project. The authors intend to arrange and describe various indexes that are needed in test facility design, construction and operation process. This technical paper is describing model analysis of damage prediction of accident in KSLV Integrated Propulsion System Test Facility based on propellant storage quantity and layout. In addition, the result can be used to produce safer design of test facility.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.25.2-25.2
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• 2011

저궤도위성의 정밀궤도결정은 GPS 위성과 수신기의 시계 공통오차를 제거하기 위해 이중 차분하는 방법으로 요구된 위치 정밀도를 충족시켜왔다. 그러나 빠른 속도로 지구를 회전하는 저궤도위성의 정밀궤도결정에 있어 이러한 이중 차분방법은 지구상에 광범위하게 분포된 지상 IGS 망 처리에 많은 계산 부담을 안고 있다. 그리고 지상 측지뿐만 아니라 저궤도위성을 이용한 기상관측 또는 긴급한 영상 처리 응용분야에서도 고정밀도 준실시간(Near Real Time-NRT) 처리가 요구되고 있다. 고정밀 준실시간 정밀궤도결정을 위한 대안은 이중주파수 GPS 수신기으로 IGS에서 제공되는 정밀궤도력을 갖고 고정밀 단독측위가 가능한 정밀단독측위(precise point positioning) 기법으로 상대측위와 버금가는 위치 정밀도를 얻을 수 있다. 다목적실용위성 5호는 고정밀 합성 레이더 영상 처리를 위해서 요구되는 20 cm 위성 위치 정밀도를 만족시키고, 대기 기상관측을 위해 GPS 전파 엄폐 측정값 수집을 목적으로 고정밀 이중주파수 GPS 수신기(Integrated GPS and Occultation Receiver, IGOR)를 탑재하고 있다. 이 논문에서는 IGOR의 이전 제품인 Blackjack 수신기를 탑재한 GRACE 위성의 실제 GPS 데이터를 사용하여 대략 3 ~ 5cm의 위치 정밀도를 얻었다. 준실시간 정밀궤도결정에서 정밀도 손실없이 궤도결정 처리 지연시간(latency)을 줄이는 것이 중요하다. 이 지연시간은 GPS 측정값의 양에 따라 크게 좌우되기에 GPS 측정값 샘플링 주기를 10초에서 640초까지 변화시켜가면서 정밀도를 분석한 결과, 위치 정밀도 손실없이도 궤도결정처리 지연시간을 단축시킬 수 있음을 제시하고 있다.

• Journal of the Korea Society of Computer and Information
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• v.28 no.2
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• pp.55-62
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• 2023

Radio waves must pass through the unstable atmosphere for successful wireless data transmission from space to ground stations. Data link algorithms required by the International Space Data Systems Advisory Committee (CCSDS) must be capable of detecting and resynchronizing cryptographic and receiver-side errors. However, error recovery is not part of the CCSDS requirements. This paper proposes an algorithm that enables robustness and error recovery against various noises. We experimented with environments such as Gaussian, Salt, Pepper, and S&P noise through noise reduction filters, filters that improve sharpness, and EDSR. In addition, we compare similar algorithms SES Alarmed and DSES Alarmed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.10
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• pp.851-868
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• 2015

A radio telescope which has been dominantly used for millimeter and submillimeter wave radio astronomy is a cassegrain antenna. A various receivers with specified observing bandwidths are installed on cassegrain antenna so as to carry out to investigate a diverse radio astronomy. A beam guiding system should be required so that a various receiver can be conducted their own observational frequency bands. The beam guiding system based on Gaussian beam transmission theory consists of quasi-optical circuit used such ellipsoidal mirror, dielectric lens and feed horn. In this paper, not only Gaussian beam transformations based on Gaussian beam theory are presented, but also design techniques for quasi-optical circuit are given. By using proposed design techniques, both Gaussian beam quasi-optical circuits to be used for cassegrain antenna and design results are also described. Properties of key focusing elements such ellipsoidal mirror and dielectric lens and feed horn are also discussed. It is expected that beam guiding system to be applied cassegrain antenna could be easily designed by using proposed design techniques.

• Journal of Astronomy and Space Sciences
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• v.25 no.1
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• pp.43-52
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• 2008

As the next generation of global satellite navigation system, the Galileo project is about to witness an initial orbit validation stage as the successful test of navigation message transmission from Giove-A in 2007. The Space Geodesy division ana the Radio Astronomy division of the Korea Astronomy & Space Science Institute had collaborated on the field survey for the Galileo Sensor Station (GSS) RF environment of the proposed site near Jeju Tamla University from August 3rd to August 5th, 2006. The power spectrums were measured in full-band $(800{\sim}2000MHz)$ and in-band (E5, E6 and L1 band) in frequency domain for 24 hours respectively. Finally, we performed a time domain analysis to characterize strong in-band interference source based on the result of the previous step.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.9
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• pp.56-65
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• 2005

A dynamic analysis method that freezes a time domain by discretization and solves the spatial propagation equation has a unique feature that provides a degree of freedom on spatial domain compared with the space discretization or space-time discretization finite element method. Using this feature, the time finite element analysis can be effectively applied to optimize the spatial characteristics of distributed type actuators. In this research, the time domain finite element method was used to discretize the model. A state variable vector was used in the discretization to include arbitrary initial conditions. A performance index was proposed on spatial domain to consider both potential and vibrational energy, so that the resulting shape of the distributed actuator was optimized for dynamic control of the structure. It is assumed that the structure satisfies the final rest condition using the realizable control scheme although the initial disturbance can affect the system response. Both equations on states and costates were derived based on the selected performance index and structural model. Ricatti matrix differential equations on state and costate variables were derived by the reconfiguration of the sub-matrices and application of time/space boundary conditions, and finally optimal actuator distribution was obtained. Numerical simulation results validated the proposed actuator shape optimization scheme.