• 전기의세계
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• v.43 no.12
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• pp.32-39
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• 1994

최근 저궤도 위성을 이용한 세계적규모의 통신서비스 제공방식이 다수 제안되고 사업화가 추진되면서 신문이나 TV등 메스컴을 통해서도 내용의 일부가 소개됨에 따라 저궤도 위성통신서비스는 일반인들에게도 그다지 낯설지 않은 용어가 되었다. 그러나 저궤도 위성통신서비스는 생각처럼 그렇게 쉽게 구현이 가능한 것은 아니며 또 현실적으로도 아직 실현을 위한 준비단계에 있으며 구체적인 실현은 몇년 후에야, 대체로 서기 2000년전으로 추정되지만, 이루어질 수 있을 것으로 보인다. 또한 사업성 전망도 다소 불투명하여 일반인들이 생각하듯이 환상적인 미래만을 약속하는 것은 아니다. 본고에서는 저궤도 위성을 이용한 통신서비스에 관하여 기본원리, 기술적 문제점 및 현안, 제안된 시스템의 분석 및 비교, 사업추진 현황등을 살펴보고 미래를 진단해보는 순서로 설명을 진행하여 일반 기술인들의 이해를 돕는데 조금이라도 도움이 되게 하였다.

• Journal of Satellite, Information and Communications
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• v.8 no.2
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• pp.74-79
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• 2013

For the purpose of drawing out a requirements (draft) for the development of low Earth orbit meteorological satellite payload, the present development situation of the foreign low Earth orbit meteorological satellite payload was analyzed, and survey and analysis on the questionnaire of the low Earth orbit meteorological satellite payload users' requirements were carried out. Through this research, some key required performance specifications (draft) were made on the basis of technological requirements such as frequency, radiation measurement, spacial, and antenna efficiency requirements, and the low Earth orbit meteorological satellite payload users' requirements.

• Aerospace Engineering and Technology
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• v.13 no.2
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• pp.142-149
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• 2014

After launch of Low Earth Orbit(LEO) satellite, Initial Activation Checkout(IAC) and Calibration and Validation(Cal & Val) procedure are performed prior to enter normal operation phase. During normal operation phase, most of the time is allocated for mission operation except following up measures to anomaly and orbit maintenance. Since mission operation capability is key indicator for success of LEO satellite program and consistent with promotion purpose of LEO satellite program, reliability should be ensured by conducting through test. In order to ensure reliability by examining the role of LEO satellite and ground station during ground test phase, realistic test scenario that is similar to actual operation conditions should be created, and test that aims to verify full mission cycle should be performed by transmitting created command and receiving image and telemetry data. This paper describes the test design and result. Consideration items for test design are described in detail and result of designed test items are summarized.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.217.2-217.2
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• 2012

저궤도위성 관제용 소형안테나시스템의 송수신채널은 저궤도위성의 특성상 안테나구동부의 물리적인 제약조건을 갖으며 이러한 제약조건은 Rotary Joint 포트 수에 의존한다. 다목적 실용위성 5호와 같이 RH 및 LH 편파를 동시 사용하는 위성의 경우 지상안테나의 RF채널은 물리적으로 4포트가 필요하게 된다. 이러한 물리적 채널을 구현하기위해서는 안테나구동부가 대형화될 뿐만 아니라 고비용의 소요된다. 이와 같이 대형화 및 고비용의 단점을 극복하기위하여 Channel Combine Filter를 적용하여 채널이중화를 구현하였으며 단일채널을 갖는 저궤도위성 지상안테나시스템을 RH 및 LH 편파를 동시수신 가능하도록 성능을 개선하였다. 금번 개발된 Channel Combiner는 하나의 물리적 채널을 이용하여 위성으로부터 수신되는 수신신호 및 지상에서 송신하는 송신신호를 동시에 전송하도록 설계한 것으로서 수신되는 신호대비 송신신호의 크기가 상대적으로 고출력이기 때문에 송수신신호간의 간섭영향을 최소화할 수 있도록 설계하였다. 따라서 본 논문에서는 채널이중화를 위하여 개발된 Channel Combiner의 설계방법 및 성능 시험결과에 대하여 상세하게 기술하였으며, 최종적으로 RH 및 LH 편파를 동시에 사용하는 저궤도 위성을 이용한 수신결과에 대하여 기술하였다.

• The KIPS Transactions:PartC
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• v.8C no.3
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• pp.367-372
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• 2001

지도제작, 해양생태감시, 기상관측, 및 우주환경감시 등의 분야에 이용되는 저궤도 위성을 관제(위성추적, 원격측정 및 명령)하기 위해 본 논문에서는 최적의 PM 변조지수를 결정하는 방법을 기술하고 수신 데이터의 성능을 평가한다. 이 저궤도 위성인 아리랑 위성은 한국에서는 첫 번째 저궤도 위성이며 1999년 12월 발사되어 현재 임무를 충실히 수행하고 있다. 아리랑 위성 관제시스템의 파라미터에 의해 위성링크를 설계하면, PB 원격측정 신호의 최적 변조지수는 Eb/No마진과 PFD마진의 교차점이 되며 1.92라디안으로 결정된다. 또한 위성의 통과시간에 따라 예측되는 BER은 RT모드에서 최고의 성능을 나타애고, RT+RNG모드에서 최악의 성능을 나타내기 때문에 데이터 전송순서를 위성의 통과시간에 따른 BER 성능 순서인 RT, PB, RT+RNG모드의 순서로 결정함으로써 수신성능을 높일 수 있다.

• The Journal of the Korea Contents Association
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• v.5 no.6
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• pp.129-137
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• 2005

A performance analysis of LEO Satellite Communication Service is being made in a variety of ways. In this paper we examined the variation of interference caused by the distribution of terminals within a cell and the maximum number of users according to the average distance between terminals, which had not been considered in former researches. Also we examined the interference made by sopt beam isolation value of some antennas(tapered-apertured antenna, gaussian antenna) which are used on LEO Satellite Communication Service Assigning this interference to the bandwidth of channels in LEO Satellite Communication Service, and with principal parameters(bandwidth, number of carrier) we made a performance analysis. And comparing tapered-apertured antenna with gaussian antenna we will find out which one is more effective and more suitable for interference.

• Aerospace Engineering and Technology
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• v.2 no.1
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• pp.54-62
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• 2003

The satellite in space has a tiny size but is subject to the disturbance torques caused by various sources. The presence of environmental disturbance torques significantly affects the orient as well as the orbital motion of satellite. The sources of environmental effects on LEO Satellite attitude dynamics are various. Four of these, gravity gradient, Earth's magnetic field, solar radiation pressure and aerodynamic are dominant and deterministic. In this study, we describe the model of environmental disturbance torques acting on LEO Satellite and the effects of environmental disturbance torques on LEO Satellite attitude dynamics in detail.

• The Bulletin of The Korean Astronomical Society
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• v.30 no.1
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• pp.56.1-56.1
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• 2005

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.10
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• pp.2256-2271
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• 1997

In this paper, we analyze the multipath fading and the inter-satellite interference considering the satellite mobility in the LEO mobile satellite communication networks and evaluate the link perfodrmance for various wave propagation environments and reliabilities of communiation system. Multipath fading is estimated by analyzing the variation of fading margin for the satellite motion in rural, urban and suburban environments. The inter-satellite interferences are classified into 8 bypes with respect to interference path. The interferences evaluated in the paper are as follows:intra-LEO satellite interference, inter-LEO satellite interference, and GEO satellite to LEO satellite interference. As a conclusion, this apaper analyzes the change of elevation anagle and propagation distance with respect to time in the LEO satellite netwoek and prosents the variation of link margin continuously.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.2
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• pp.147-158
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• 2020

In this paper, we will review the thruster based reaction wheel momentum dumping method for low Earth orbit satellite. Thruster based momentum dumping is widely used in GEO satellites by performing momentum dumping and attitude control using thrusters at the specific time. LEO satellite should perform momentum dumping at any time, thus it is not appropriate to use GEO satellite's momentum dumping method. In this research, we will review the method for LEO satellite, which perform momentum dumping always and use reaction wheels for attitude control during dumping. To reduce thruster's valve on and off counts, we propose to use the maximum pulse width for thruster operation. To prevent attitude error increase by thrusters, we adjust the thruster operation interval. Through simulation, we verify the proposed method's effects.