• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.248-250
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• 2003

Thermal analysis is performed to protect the propulsion system of low-earth-orbit earth observation satellite from unwanted thermal disaster like propellant freezing. To implement thermal design adequately, heater powers for the propulsion system estimated through the thermal analysis are decided. Based on those values anticipated herein, the average power for propulsion system becomes 22.02 watts when the only one redundant catalyst bed heater is turned on. When for the preparation of thruster firing, 25.93 watts of the average power is required. All heaters selected for propulsion components operate to prevent propellant freezing meeting the thermal requirements for the propulsion system with the worst-case average voltage, i.e. 25 volts.

• Journal of Astronomy and Space Sciences
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• 제31권1호
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• pp.67-72
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• 2014

The next generation small satellite-1 (NEXTSat-1) program has been kicked off in 2012, and it will be launched in 2016 for the science missions and the verification of space core technologies. The payloads for these science missions are the Instrument for the Study of Space Storms (ISSS) and NIR Imaging Spectrometer for Star formation history (NISS). The ISSS and the NISS have been developed by Korea Advanced Institute of Science and Technology (KAIST) and Korea Astronomy and Space science Institute (KASI) respectively. The ISSS detects plasma densities and particle fluxes of 10 MeV energy range near the Earth and the NISS uses spectrometer. In order to verify the spacecraft core technologies in the space, the total of 7 space core technologies (SCT) will be applied to the NEXTSat-1 for space verification and those are under development. Thus, the operation modes for the ISSS and the NISS for space science missions and 7 SCTs for technology missions are analyzed for the required operation time during the NEXTSat-1's mission life time of 2 years. In this paper, the operational concept of the NEXTSat-1's science missions as well as the verification of space core technologies are presented considering constraints of volume, mass, and power after launch.

• International Journal of Aeronautical and Space Sciences
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• 제4권2호
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• pp.17-25
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• 2003

Simple methods are developed to predict temperatures of a satellite box during launch stage. The box is mounted on outer surface of satellite and directly exposed to space thermal environment for the time period from fairing jettison to separation. These simple methods are to solve a 1st order ordinary differential equation (ODE) which is simplified from the governing equation after applying several assumptions. The existence of analytical solution for the 1st order ODE is determined depending on treatment of time-dependent molecular heating term. Even for the case that the analytical solution is not available due to the time dependent term, the 1st order ODE can be solved by relatively simple numerical techniques. The temperature difference between two different approaches (analytical and numerical solutions) is relatively small (Jess than $1^{\circ}C$ along the time line) when they are applied to STSAT-I launch scenario. The present methods can be generally used as tools to quickly check whether a satellite box is safe against space environment during the launch stage for the case that the detailed thermal analysis is not available.

• Journal of Mechanical Science and Technology
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• 제18권5호
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• pp.847-856
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• 2004

Heaters for the spacecraft propulsion system are sized to prevent propellant from catastrophic freezing. For this purpose, thermal mathematical model (TMM) of the propulsion system is developed. Calculation output is compared with the results obtained from thermal vacuum test in order to check the validity of TMM. Despite a little discrepancy between the two types of results, both of them are qualitatively compatible. It is concluded that the propulsion system heaters are correctly sized and TMM can be used as a thermal design tool for the spacecraft propulsion system.

• 한국위성정보통신학회논문지
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• 제8권1호
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• pp.35-39
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• 2013

우주 산업은 21세기 가장 경쟁력 있는 산업으로 부각되는 미래의 핵심 산업이다. 하지만 우주 산업은 인프라 구축에 초기 투자비용이 막대하여 단기에 투자비용을 회수하기 어려운 면이 있어 민간 기업이 독자적으로 우주 사업을 수행하는 것은 한계가 있다. 따라서 미국, 일본 등 우주 산업 선진국들은 초기에 정부의 정책지원으로 일정수준까지 우주 기술발전을 도모하여 왔다. 우리나라는 2005년 우주개발진흥법의 제정과 국가우주개발중장기기본계획의 수정 등 제도적인 보완 노력을 하고 있다. 하지만 우리나라가 세계 8대 경제 대국으로 성장할 동안 위성을 독자 개발하여 국내 수요를 충족하고 수출할 정도의 능력을 가진 대기업이 없는 실정이다. 따라서 본 논문에서는 우리나라 우주개발 임무를 효율적으로 추진하고 국제 경쟁력을 강화하기 위한 위성산업 활성화 방안을 제시하였다.

• 한국위성정보통신학회논문지
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• 제11권4호
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• pp.89-93
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• 2016

본 논문에서는 정지궤도관측위성의 영상품질 보장과 이에 기반한 성공적 임무수행을 위해 필수불가결한 구성요소인 INR (Image Navigation and Registration) System의 핵심적 기술 요체를 요약하여 기술한다. 이를 위해, 그 원천기술의 모태인 최초 INR System의 근원과 이후 다른 위성시스템들을 통해 부분적 변화를 거쳐 구현된 변천과정을 검토하고, 그 핵심 구성요소와 각 구성요소의 기술적 요체를 기술하며, 이러한 기술적 요체를 포괄적으로 반영하며 과거와 현재 및 미래의 다양한 INR System들에 공통적으로 적용될 수 있는 generic한 INR system 구성을 제안한다. 이는 INR System 개발의 표준적 접근방법을 제시하고 그 핵심적 기술사항과 추가적 발전가능 영역을 규명함으로써 향후의 INR System 개발, 검증 및 운용에 있어 하나의 지표로 삼고자 하기 위함이다.

• 대기
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• 제13권4호
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• pp.71-79
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• 2003

We present a pre processing system for the Atmospheric Infrared Sounder (AIRS) sounding suite onboard Aqua satellite. With its unprecedented 2378 channels in IR bands, AIRS aims at achieving the sounding accuracy [s1]of a radiosonde (1 K in 1-km layer for temperature and 10% in 2-km layer for humidity). The core of the pre p rocessor is the International MODIS/AIRS Processing Package (IMAPP) that performs the geometric and radiometric correction to compute the Earth's radiance. Then we remove spurious data and retrieve the brightness temperature (Tb). Since we process the direct-broadcast data almost for the first time among the AIRS directbroadcast community, special attention is needed to understand and verify the products. This includes the pixel-to-pixel verification of the direct-broadcast product with reference to the fullorbit product, which shows the difference of less than $10^{-3}$ K in IR Tb.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -2
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• pp.1320-1323
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• 2002

This paper reviews the Korean government’s selection process of core wireless communications technologies, and presents technology trends, perspectives and strategies of 5 core technologies to develop in wireless communications areas based on the mid term IT technology development plan(2002∼2004). Delphi Panel Method and Analytic Hierarchy Process(AHP) Analysis were adapted to select 30 core technologies in 9 strategic areas. Especially, 5 core wireless communications technologies out of 24 required technologies are selected: 4 G Core Technology, Broadband Wireless Access Network Technology, IMT-2000 Plus STP Technology, OBP Based Multimedia Satellite Communications Technology, Stratosphere Communications System Technology. Strategic national IT R&D program has been essential to continue success story of CDMA technology, and acquiring technology independency from advanced nations. In long term perspectives, a strategy of intensive investment with prudent selection onto core technologies should be deployed in the IT R&D programs. Also, the national IT R&D programs should be limited in the high risk & high returen areas where only government can afford the failures as well as better spill over effects are expected for the technology development and national economy. Korean industry has some strength in wireless communications technology area. Therefore, more policy concerns should be given into this area not only to secure present strength but also to explore better technology competitiveness.

• 기술사
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• 제34권4호
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• pp.36-40
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• 2001

Multimedia service via satellite Is supported voice, data, Image and video signals. The representation case model of satellite multimedia are satellite TV. satellite Internet. In the early 1990s, satellite communication and broad casting services successfully expanded form C/Ku band to Ka band. The benefits of operation at Ka-band are greater bandwidth available to accommodate the increased demand for high-speed Information exchange. By the early years of the 21s1 century, millions of households worldwide with dual Ku / Ka-band dishes Satellite multimedia systems receive hundreds of TV channels, originating from around the world, and delivering entertainment, information and education. Many Ku-band satellites have been ordered, but few Ka-band systems are moving into production. So Ka-band systems are characterized that low-cost access to low and high peed, two-way voice, data, and video communications.

• 대한원격탐사학회지
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• 제21권5호
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• pp.371-382
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• 2005

We present a processing system for the Atmospheric Infrared Sounder (AIRS) sounding suite onboard Aqua satellite. With its unprecedented 2378 channels in IR bands, AIRS aims at achieving the sounding accuracy of radiosonde (1 K in 1-km layer for temperature and $10\%$ in 2-km layer for humidity). The core of the processor is the International MODIS/AIRS Processing Package (IMAPP) that performs the geometric and radiometric correction for generation of Level 1 brightness temperature and Level 2 geophysical parameters retrieval. The processor can produce automatically from received raw data to Level 2 geophysical parameters. As we process the direct-broadcast data almost for the first time among the AIRS direct-broadcast community, a special attention is paid to understand and verify the Level 2 products. This processor includes sub-systems, that is, the near real time validation system which made the comparison results with in-situ measurement data, and standard digital information system which carry out the data format conversion into GRIdded Binary II (GRIB II) standard format to promote active data communication between meteorological societies. This processing system is planned to encourage the application of geophysical parameters observed by AIRS to research the aqua cycle in the Korean peninsula.