• Journal of Satellite, Information and Communications
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• v.10 no.2
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• pp.102-108
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• 2015

In general, two way satellite communication systems based on TDMA(Time Division Multiple Access) require network clock synchronization between hub station and remote terminals. This paper describes basic concepts for network clock synchronization based on NCR(Network Clock Reference) clock recovery scheme as suggested in DVB-S2/ RCS2 international standards. in addition, a new NCR insertion method has been proposed and evaluated in terms of supporting CCM mode as well as ACM mode which optimizes throughput by changing code rates and modulation types ranging from QPSK to 32-APSK.

• The Journal of the Convergence on Culture Technology
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• v.8 no.3
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• pp.259-263
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• 2022

As urbanization progresses in Korea, megacities are being formed around the metropolitan area, the central area, and the southeast area. In addition, it is accelerating the development of urban air mobility (UAM) that can be operated by Mega City as a new growth engine industry in the future. At the same time, in order to become a space powerhouse, Korea plans to establish its own Korean positioning system (KPS) by 2035. Therefore, if urban air mobility and location information services provided by the Korean positioning system are used in combination, urban air mobility can be stably operated in future megacities.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.3
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• pp.93-98
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• 2005

STSAT-2 will be launched on December 2007 by the first Korean launch vehicle KSLV-1, and its one of the main instruments is DREAM (Dual Channel Radio Frequency and Environment Atmosphere Monitoring) which detects a signal for atmosphere from the Earth by using micro-wave signal. The STSAT-2 has many units for technology demonstration such as FDSS (Fine Digital Sun Sensor) and DHST (Dual Head Star Tracker) including PPT (Pulsed Plasma Thruster) for attitude control and momentum dumping in the space. In this paper, the power budget analysis for STSAT-2 will be studied and provided for supporting the whole mission life time during the mission of its spacecraft.

• Current Industrial and Technological Trends in Aerospace
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• v.8 no.2
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• pp.54-64
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• 2010

A spacecraft contends with various vibration from the launch to the on-orbit operation, which is one of the major considerations in spacecraft design. The weight reduction has been indispensable to decrease the launch cost, however it produces worse disturbances for the spacecraft equipments. Besides, the load requirements at observation payload interfaces have became severe to secure their pointing stability as their images are required with high resolution. As a possible solution, a vibration isolation system is introduced and it reduces the vibration from the launch vehicle or isolates the spacecraft equipments from their generating/transmitted vibration. In this paper, it is examined the design consideration needed for the accommodation of the vibration isolation systems through the survey of recent applications of vibration mitigation technologies to spacecrafts.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.187-196
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• 2009

Synthetic Aperture Radar(SAR) satellite system for broad-area imaging has RF systems including SAR radiating a high power, data link system transmitting the acquired image data from the SAR, TC&R(Telemetry, Command, and Ranging) to communicate with a ground segment to control a satellite. Each system transmits RF signal having various frequencies and radiates a high power, RS(Radiated Susceptibility) specification should be verified at an electronic unit mounted in satellite. RF interference can be happened because of non-linearity of a RF system. Therefore, we manufactured a structure model installed antennas which have a similar pattern with a real antenna, the effect by RF interference is analyzed and verified.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.1
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• pp.62-71
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• 2015

Geostationary satellites use the thruster in order to control the location change and mount the suitable amount of liquid propellant depending on the operating lifetime. Therefore the lifetime of the geostationary satellite depends on the residual propellant amount and the precise residual propellant gauging is very important for the mitigation of economic losses arised from premature removal of satellite from its orbit, satellites replacement planning, slot management and so on. The propellant gauging methods of geostationary satellite are mostly used PVT method, thermal mass method and bookkeeping method. In this paper, we analysis the modeling of COMS(Communication, Ocean & Meteorological Satellite) bipropellant system for bookkeeping method and COMS GTO(Geostationary Transfer Orbit) injection propellant estimation using Monte-Carlo method.

• Journal of Satellite, Information and Communications
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• v.1 no.1
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• pp.48-53
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• 2006

A K-SBAS (Korean Satellite Based Augmentation System) is proposed as one of the space infrastructure. The proposed system considers the existed elements to the utmost for the most economical SBAS construction. As reference system the current DGPS (differential global positioning system) network is investigated. Space segment is investigated based on the COMS-1 (Communications, Oceanographic, and Meteorological Satellite-1). While bus system of COMS-1 can be kept to minimum change, the communication payload of needed, crucial parts such as software, man power can be easily secured through the DGPS network operation heritage.

• 전기의세계
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• v.39 no.5
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• pp.10-18
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• 1990

위성통신의 이용과 기술발전 추세를 살펴보면, 1950/60년대에는 미국, 프랑스 소련 및 영국을 중심으로 국방 및 과학기술측면에서 위성을 보유운용 하였으나, 1970/80년대에는 브라질, 호주, 중국, 인도 및 인도네시아와 같이 국토면적이 넓거나 섬이 많은 국가에서 위성의 특징을 활용하였다. 그리고 1990년대 이후에는 새로운 정보통신 및 방송서비스 영역을 확장하기 위해 개발도상국에 이르기까지 위성의 이용은 상당히 증대될 것으로 기대된다. 또한 선진각국들은 최근 급속한 발전을 이룩한 디지틀 신호처리기술, 부품 및 소자기술 등을 이용하여 다기능 및 고효율성을 갖는 위성시스팀 개발을 진행해오고 있다.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.193-195
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• 2005

전력계통의 안정적인 운용을 위해서는 현재 운전 중인 계통의 운용데이터를 수집하여 분석하고 그에 따라 적절한 제어를 하는 것이 매우 중요한 일이다. EMS가 이러한 일을 처리하고 있으며, 여기서 상태추정기는 정확한 계통 운용 데이터베이스를 제공하는 역할을 한다. 지금까지 모든 데이터는 동시에 측정이 되었다는 가정 하에 상태추정 연산을 하였으나, 실제로 모든 데이터 측정의 동기성을 확보하는 것은 사실상 불가능하다. 최근 인공위성에 의해 동기화된 PMU(phasor measurement unit)가 전력계통 운용에 사용되고 있다. 본 논문에서는 PMU로부터 얻을 수 있는 전압 및 전류 데이터를 상태추정에 이용하는 방법을 개발하였다. 위성에 의해 동기화된 페이저 측정데이터는 데이터 측정의 동기성 확보뿐만 아니라, 데이터의 정밀도 및 위상각의 직접적인 측정이라는 둥의 여러 가지 면에서 매우 효용성이 높은 데이터이다. 본 연구를 통해 개발된 상태추정 프로그터은 IEEE 30모선 시험계통을 이용하여 그 타당성을 검증하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.17-22
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• 2006

Anhydrous hydrazine and its methyl derivatives MMH and UDMH have been safety used as monopropellant and bipropellant fuels in thousands of satellites and expendable launch vehicles. Since KOMPSAT program, We have been developing skills on the hydrazine propulsion system for several years. This paper presents an overview of the hydrazine for the space application - propellant overview, material compatibility, handling cautions and the future of hydrazine systems.