• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2006년도 한국우주과학회보 제15권1호
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• pp.77-77
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• 2006

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1465-1469
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• 2003

In general satellite verification process, the AOCS (Attitude & Orbit Control Subsystem) should be verified through several kinds of verification test which can be divided into two major category like FBT (Fixed Bed Test) and polarity test. And each test performed in different levels such as ETB (Electrical Test Bed) and satellite level. The test method of FBT is to simulate satellite dynamics with sensors and actuators supported by necessary environmental models in ETB level. The VDS (Vehicle Dynamic Simulator) try to make the real situation as possible as the on-board processor will undergo after launch. The purpose of FBT test is to verify that attitude control logic function and hardware interface is designed as expected with closed loop simulation. The VDS is one of major equipments for performing FBT and consists of software and hardware parts. The VDS operates in VME environments with target board, several commercial boards and custom boards based on the VxWorks real time operating system. In order to make time synchronization between VDS and satellite on-board processor, high reliable semaphore was implemented to make synchronization with the interrupt signal from on-board processor. In this paper, the real-time operating environment used on VDS equipment is introduced, and the hardware and software configurations of VDS summarized in the systematic point of view. Also, we try to figure out the operational concept of VDS and AOCS verification test method with close-loop simulation.

• ETRI Journal
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• 제27권1호
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• pp.43-52
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• 2005

In this paper, we introduce an adaptive radio resource allocation for IP-based mobile satellite services. We also present a synchronous multibeam CDMA satellite system using an orthogonal resource sharing mechanism among downlink beams for the adaptive packet transmission. The simulation results, using a Ka-band mobile satellite channel and various packet scheduling schemes, show that the proposed system and resource allocation scheme improves the beam throughput by more than two times over conventional systems. The simulation results also show that, in multibeam satellite systems, a system-level adaptation to a user's channel and interference conditions according to user locations and current packet traffic is more efficient in terms of throughput improvement than a user-level adaptation.

• Journal of Astronomy and Space Sciences
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• 제30권1호
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• pp.1-10
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• 2013

An integrated orbit and attitude control algorithm for satellite formation flying was developed, and an integrated orbit and attitude software-in-the-loop (SIL) simulator was also developed to test and verify the integrated control algorithm. The integrated algorithm includes state-dependent Riccati equation (SDRE) control algorithm and PD feedback control algorithm as orbit and attitude controller respectively and configures the two algorithms with an integrating effect. The integrated SIL simulator largely comprises an orbit SIL simulator for orbit determination and control, and attitude SIL simulator for attitude determination and control. The two SIL simulators were designed considering the performance and characteristics of related hardware-in-the-loop (HIL) simulators and were combined into the integrated SIL simulator. To verify the developed integrated SIL simulator with the integrated control algorithm, an orbit simulation and integrated orbit and attitude simulation were performed for a formation reconfiguration scenario using the orbit SIL simulator and the integrated SIL simulator, respectively. Then, the two simulation results were compared and analyzed with each other. As a result, the user satellite in both simulations achieved successful formation reconfiguration, and the results of the integrated simulation were closer to those of actual satellite than the orbit simulation. The integrated orbit and attitude control algorithm verified in this study enables us to perform more realistic orbit control for satellite formation flying. In addition, the integrated orbit and attitude SIL simulator is able to provide the environment of easy test and verification not only for the existing diverse orbit or attitude control algorithms but also for integrated orbit and attitude control algorithms.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2004년도 한국우주과학회보 제13권2호
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• pp.300-303
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• 2004

KOMPSAT-2 satellite mission operations and control system has been developed by ETRI. The system functional architecture, analysis and design, implementation, and tests are presented in this paper.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.180.1-180.1
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• 2005

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 추계 학술대회논문집
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• pp.137-139
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• 2004

The monopropellant hydrazine thrusters are widely used for the satellite on-board propulsion system fulfilling various missions in space. They have outstanding features caused by the nearly unlimited restart capability and the very high credibility. The sole monopropellant thruster used at precent in nation is MRE-1 that is a standard component of NASA. It can produce 4.45 N of nominal thrust. Due to the glowing complexity with a satellite mission, the needs for thrusters of the diverse performance are being increased. The numerical simulation could give useful information to develop a new type thruster instead of the experiments performed previously. Therefore it is critical to make a reliable computer code to prepare design change of a thruster. In this paper, the performance analysis and validation of the satellite monopropellant hydrazine thruster currently used is accomplished as the preliminary study to serve valuable data for future design change.

• 한국통신학회논문지
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• 제29권10A호
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• pp.1167-1176
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• 2004

본 논문에서는 위성 하향 링크에서 강우 감쇄와 음영 페이딩에 대한 적응형 전송을 위한 MC-CDMA(multicarrier CDMA) 방식을 제시하고, Ka 대역 이동위성채널에서 페이딩, 강우 감쇄, 재전송 방식에 따른 적응형 MC-CDMA 하향링크의 성능을 비교 분석하였다. 제시된 하향 링크는 광대역 MC-CDMA 전송을 통해 수십 Mbit/s 처리율과 채널 환경에 따라 약 1 bit/s/Hz에서 4.7 bit/s/Hz의 주파수 효율을 제공할 수 있다.

• 한국위성정보통신학회논문지
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• 제7권1호
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• pp.92-96
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• 2012

본 논문은 복잡한 신호처리 기능을 포함하는 리턴 링크 복조 알고리즘이 낮은 SNR에서도 안정적으로 동작하도록 하기 위해 하드웨어에 적합하도록 설계하여 HDL로 구현하는 것을 목적으로 한다. 모의실험 결과 Uncoded BER $10^{-3}$ 지점에서의 Es/$N_0$가 이상적인 QPSK 신호 대비 0.5dB 이내로의 성능개선을 이룬 것을 확인할 수 있다. 또한 이에 대한 Fixed-Point Simulation 및 HDL 구현 성능이 모의실험 대비 차이가 없음을 확인할 수 있다.

• 한국전자통신학회논문지
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• 제9권4호
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• pp.439-446
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• 2014

본 연구는 디지털위성중계기의 우주인증 모델에 대한 성능분석 및 구현에 대해 기술하였다. 사전 성능 분석은 각 구성품 회로 시뮬레이션을 통해 각 구성품에 대한 요구 규격 대비 만족 여부를 사전 검증하고, 각각의 구성품을 순서대로 연결하여 전체적인 디지털위성중계기의 요구 규격에 만족하는지를 사전 검증하였다. 사전 시스템 성능 분석을 통하여, 각 구성품의 요구 규격을 정의하고, 그 규격을 바탕으로 제작하였으며, 최종적으로 시스템 통합하여 전체적인 디지털위성중계기의 성능 측정을 하였다.