• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.2
• /
• pp.133.1-133.1
• /
• 2011

태양풍이 지구 전파통신에 미치는 영향을 예측하고 대응하기 위해 전파연구소와 협력하여 태양풍의 운동을 모니터할 수 있는 시스템을 개발하고 있다. 태양풍이 일으키는 섬광(scintillation)에 의해 태양풍 배후에 있는 전파원 밝기가 변하는 것을 측정하여 역으로 태양풍의 이동속도, 전자밀도 등을 유도하는 원리를 이용한다. 포물면형의 전파망원경 대신 시야가 넓은 다이폴 안테나를 24개 단위로 묶은 타일 32개를 동서-남북으로 수백미터 넓이의 부지에 배열하고 전자빔조향으로 원하는 천체를 추적한다. 타일은 수동으로 남북방향으로 움직일 수 있어 계절별로 태양근처의 전파원을 잘 볼 수 있도록 하였다. 각 타일에서 나온 신호는 약 10MHz의 대역폭으로 디지털화되어 컴퓨터에 기록되고 실시간에 가깝게 각 타일간의 천체 위치별 위상차를 보정한 후 합성되어 전파원의 세기를 측정한다. 이 신호들을 교차상관시키면 야간에는 천문용 간섭계로도 사용할 수 있다. 기본적으로는 MWA를 참고해서 설계한 것이나, 동작을 입증하기 위해서 타일 3개로 이루어진 시제품도 제작하였다. 현재 각 부분별로 제작이 진행되고 있으며 하드웨어는 올해 말까지 완성될 것이다.

• Journal of Astronomy and Space Sciences
• /
• v.14 no.1
• /
• pp.67-79
• /
• 1997

We have designed the quasi optics of the dual channel receiver to observe the radio sources with 100GHz-band and 150GHz-band simultaneously. We introduced the general quasi optics and the relation between the Gaussian beam and thin lens approximation. We determined the parameters of the quasi optic components to match the beam waist at cassegrain focus with that of feed horn well.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.191.1-191.1
• /
• 2012

저궤도 위성은 대구경 광학 탑재체를 장착한 지구관측 위성으로 자세제어 센서, 탑재 데이터 전송 안테나 및 탑재체가 정밀하게 장착되어야 한다. 이를 위해 정밀한 장착을 설계과정에서 검토 및 해석을 하기 위한 요구조건을 설정하고, 요구조건을 분석하는 과정을 거치게 된다. 분석이 수행되면 이 결과를 근거로 능동적인 정열오차 교정이 필요한지, 또는 단순히 위치 정열에 대한 측정만이 필요한지를 결정한다. 그리고 측정장비의 시야각 검증 및 위치정열 측정 방안을 검토 한 후 장비들의 위치 정렬 측정 시험을 통해 정확한 위치를 확인하고, 요구조건과 비교하여 만족하는지 확인하게 된다. 다시 말해서, 위성체에 장치된 각종 장비들이 설계된 위치에 정확히 위치하고 있는지 확인하는 과정이다. 본 논문에서는 저궤도위성의 정렬 요구조건 분석 및 측정 시험을 수행한 내용을 기술하고자 한다.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.183.2-183.2
• /
• 2012

최근 인공위성의 대형화 및 중량화 추세는 종종 기존 설비 내에서의 위성체 조립 및 시험업무의 작업성과 능률성을 심각하게 저해하는 요소로 작용한다. 이에 상기 업무의 원활한 수행을 위해서는 최적화된 설계의 기계지상지원장비(Mechanical Ground Support Equipment, MGSE)의 개발 및 활용이 요구되어지며, 이는 전체 위성개발기간 동안 요구되는 모든 시험 구성, 외부 설비 및 장비와의 인터페이스, 작업자의 동선 및 접근성 등을 종합적으로 고려해야 하는 작업이다. 특히 고해상도 영상안테나와 같이 높은 수준의 정렬 조건이 부과되는 탑재체의 경우 이의 장착, 정렬 및 지상전개시험 등을 위해서는 탑재체 및 위성체의 특성을 고려한 전용 장비의 개발도 필수적이다. 본 논문에서는 한국항공우주연구원이 최근 개발한 중대형급 지상관측 영상레이더 위성 개발 과제에 활용된 기계지상지원장비의 설계, 제작 및 운용 방법을 종합적으로 기술하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.30 no.3
• /
• pp.202-208
• /
• 2019

In this study, an active element pattern (AEP) of a printed dipole was analyzed in 1D and 2D arrays. First, an AEP of the printed dipole was obtained using the simulation in the 2D infinite array. The scan blindness in the 2D array occurred in the E-plane direction at around ${\pm}36^{\circ}$; however, it was barely observed in the 1D array. To analyze the cause of the scan blindness in the 2D array, the dispersion properties of a unit cell was obtained and compared with the scan blindness by frequency change. The difference between the scan blindness of the 1D and 2D arrays was clarified using the comparison of the Q value in the unit cell in the 1D and 2D arrays. Then, the coupling of the electric field in the E-plane direction was observed when nine elements were separated between the two ports in a linearly arranged dipole structure. Finally, the printed dipole array was fabricated, and an AEP was measured for the $11{\times}1$ and $11{\times}3$ sub arrays. The proposed theory was verified using these observations and by comparison with the simulation results.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.36D no.3
• /
• pp.34-40
• /
• 1999

Recently, the gate oxide damage induced by the plasma processes has been one of the most significant reliability issues as the gate oxide thickness falls below 10 nm. The plasma-induced damage was studied with the metal antenna test structures. In addition to the electron trapping, the hole trapping in a 10 nm thick gate oxide due to the plasma-induced charging was observed in the NMOS's with a metal antenna. The hole trapping caused the transconductance (gm) to be reduced like the case of the electron trapping, but to the extent much less than the electron trapping. It would be because the electrical stress that the plasma-induced charging forced to the gate oxide for the devices with the hole trapping was much smaller than for those with the electron trapping. This hypothesis was strongly supported by the measured characteristics of the Fowler-Nordheim current in the gate oxide.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.46 no.5
• /
• pp.410-418
• /
• 2018

This paper describes the design, analysis, and verification tests of the Dual-axis X-band antenna pointing mechanism(XAPM) that has been developed for the Earth observation mission at low Earth orbits. Based on the experience of development and operation of the similar system, we defined the main points and requirements of the system design and confirmed the characteristics of the system through the verification test of the launch and orbit environment test of the engineering qualification model. Through the characteristics and verification techniques of the system acquired during this process, improvement points of the later qualification model are derived.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2010.04a
• /
• pp.201-206
• /
• 2010

A project for construction of Korea Geodetic VLBI has officially started in Oct. 2008. The construction of all system will be completed by the end of 2011. The project was named Korea VLBI system for Geodesy (KVG), and its main purpose is to maintain the Korea Geodetic Datum. In case of the KVG system, an observation room where an H-maser frequency standard is located is in a building separated from an antenna by several tens of meters. Therefore KVG system will adopt a so-called round-trip system to transmit reference signals to the antenna with diminishing the effect of path length variations. KVG's round-trip system is designed not only available to use either metal or optical fiber cables, but also available to measure path length variations directly by using K5/VSSP32 sampler. We will present principle of round-trip system and the new type of round trip system for KVG.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.40 no.5
• /
• pp.439-445
• /
• 2012

The COMS(Communication, Ocean, and Meteorological Satellite) is subjected to shock loads when the stage or fairing of a launch vehicle is separated and the satellite is separated from the launch vehicle during the launch vehicle flight. And, after the satellite is separated from the launcher, the COMS is subjected to shock loads when the solar array is deployed, Ka-Band communication antenna is deployed, and meteorological imager radiator cover is released. In order to validate the satellite safety against these shock loads on ground, shock tests were performed. In this paper, the shock tests performed in the course of the COMS development are described, and the method to assess the test result is presented with an example of Geostationary Ocean Color Imager(GOCI). In Ariane-5 launch vehicle, the clampband release shock for satellite separation is lower than the fairing or stage separation. In this paper, the extrapolation method to take into account the maximum shock load from the launch vehicle by using the satellite separation shock test result is also introduced.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.10
• /
• pp.1001-1007
• /
• 2013

In the case of multi-mission LEO(Low Earth Orbit) operations, depending on the orbit of each satellite, one ground site is supposed to be communicated with more than two satellites at the same time. On top of that, image data processing system is generally mission-specific and 1:1 backup configuration. For the reason, if ground site has smaller number of antenna than that of satellite, interface with image data processing system would be very complicated. In this paper, considering that two LEO satellites can be operating and image data recording unit in redundancy can be easily plug-in, the implementation of matrix receiving structure is described. This matrix receiving structure has been validated from KOMPSAT-2 and -3(KOrea Multi-Purpose SATellite-2 and -3) since KOMPSAT-3 was launched in May, 2012. This structure will be applied for the KOMPSAT-3A and -5 through its expandability.