• International Journal of Aeronautical and Space Sciences
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• 제14권1호
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• pp.11-18
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• 2013

Human spaceflight experience in extra-vehicular activity (EVA) is limited to two regimes: the micro-gravity environment of Earth orbit, and the lunar surface environment at one-sixth of Earth's gravity. Future human missions to low-gravity bodies, including asteroids, comets, and the moons of Mars, will require EVA techniques that are beyond the current experience base. In order to develop robust approaches for exploring these small bodies, the dynamics associated with human exploration on low-gravity surface must be characterized. This paper examines the translational and rotational motion of an astronaut on the surface of a small body, and it is shown that the low-gravity environment will pose challenges to the surface mobility of an astronaut, unless new tools and EVA techniques are developed. Possibilities for addressing these challenges are explored, and utilization of the International Space Station to test operational concepts and hardware in preparation for a low-gravity surface EVA is discussed.

• 항공우주기술
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• 제3권1호
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• pp.86-96
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• 2004

우주 환경은 두꺼운 대기층에 의해 보호되는 지표 환경에서는 경험할 수 없는 여러 가지 위험 요소가 있다. 근 지구 궤도에서는 플라스마 대기 및 원자 산소 등에 의해 부식이 발생할 수 있으며, 강한 자외선과 입자 복사 등에 의해 위성을 구성하고 있는 재료나 전자 부품 등이 손상을 입을 수 있다. 따라서 위성의 설계 시에는 운용궤도에서 예상되는 환경요인을 적절히 예측하여 이에 대응하는 설계가 이루어지도록 해야 한다.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2006년도 한국우주과학회보 제15권2호
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• pp.157-157
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• 2006

• Journal of Semiconductor Engineering
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• 제2권1호
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• pp.119-124
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• 2021

Along with the needs for feasibility in the field of space applications, interests in radiation-hardened electronics is growing rapidly. Gallium nitride (GaN)-based devices have been widely researched so far owing to superb radiation resistance. Among them, research on the most abundant protons in low earth orbit (LEO) is essential. In this paper, proton irradiation effects on parameter changes, degradation mechanism, and correlation with reliability of GaN-based devices are summarized.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.645-648
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• 2005

The COMS(Communication, Ocean and Meteorological Satellite), a multi-mission geo-stationary satellite, is being developed by KARl. The first mission of the COMS is the meteorological image and data gathering for weather forecast by using a five channel meteorological imager. The second mission is the oceanographic image and data gathering for marine environment monitoring around Korean Peninsula by using an eight channel Geostationary Ocean Color Imager(GOCI). The third mission is newly developed Ka-Band communication payload certification test in space by providing communication service in Korean Peninsula and Manjurian area. There were many low Earth orbit satellites for ocean monitoring. However, there has never been any geostationary satellite for ocean monitoring. The COMS is going to be the first satellite for ocean monitoring mission on the geo-stationary orbit. The meteorological image and data obtained by the COMS will be distributed to end users in Asia-Pacific area and it will contribute to the improved weather forecast.

• 한국군사과학기술학회지
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• 제14권5호
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• pp.842-849
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• 2011

The transponder simulator designed to simulate the transponder of military satellite communication systems in the geostationary orbit is required to have time delay function, because of 250 ms delay time, when a radio wave transmits the distance of 36,000 km in free space. But, it is very difficult to develop 250 ms time delay device in the transponder simulator of 100 MHz bandwidth, due to unstable operation of FPGA, loss of memory data for the high speed rate signal processing. Up to date, bandwidth of the time delay device is limited to 45 MHz bandwidth. To solve this problem, we propose the new time delay techniques up to 100 MHz bandwidth without data loss. Proposed techniques are the low speed down scaling and high speed up scaling methods to read and write the external memory, and the matrix structure design of FPGA memory to treat data as high speed rate. We developed the satellite link simulator in 100 MHz bandwidth using the proposed new time delay techniques, implemented to the transponder simulator and verified the function of 265 ms time delay device in 100 MHz bandwidth.

• Journal of Astronomy and Space Sciences
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• 제20권4호
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• pp.393-402
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• 2003

The Multi-Spectral Camera (MSC) is the payload of KOMPSAT-2 which is designed for earth imaging in optical and near-infrared region on a sun-synchronous orbit. The telescope in the MSC is a Ritchey-Chretien type with large aperture. The telescope structure should be well stabilized and the optical alignment should be kept steady so that best images can be achieved. However, the MSC is exposed to adverse thermal environment on the orbit which can give impacts on optical performance. Solar incidence can bring non-uniform temperature rise on the telescope tube which entails unfavorable thermal distortion. Three ways of preventing the solar radiation were proposed, which were installing external mechanical shield, internal shield, and maneuvering the spacecraft. After trade-off study, internal sun shield was selected as a practical and optimal solution to minimize the effect of the solar radiation. In addition, detailed designs of the structure and sunshield were produced and analyses have been performed. The results were assessed to verify their impacts to the image quality. It was confirmed that the internal sunshield complies with the requirements and would improve image quality.

• Journal of Astronomy and Space Sciences
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• 제13권2호
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• pp.30-40
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• 1996

우리별 1,2호의 원격명령부는 지상의 지구국, 또는 위성내 부 컴퓨터로부터 위성의 각부분을 제어하는 명령을 수신하여 적절한 전기적인 신호로 해당 부분에 전달하는 역할을 한다. 원격검침부는 위성의 건강 상태나 운영 상태를 나타내는 각종 정보를 취합하여 지상으로 전달하는 역할을 한다. 원격 검침 및 명령부를 이용하여 위성내의 나머지 부분들을 제어할 수 있으며, 또한 동작 상태를 측정할 수 있으므로 위성내의 어느 시스템보다도 높은 신뢰도가 요구되는 시스템이다. 특히, 저궤도 소형위성이라는 특수한 상황을 고려하여 설계되었으며, 위성 시스템의 전체 구성이 효율적으로 이루어질 수 있도록 개발되었다. 우리별 1, 2호는 1992년 8월과 1993년 9월에 각각 발사되어 지금까지 성공적으로 운용되고 있으며, 탑재된 원격검침 및 명령부도 정상적인 동작을 하고 있다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1998년도 Proceedings of International Symposium on Remote Sensing
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• pp.355-360
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• 1998

A small package of plasma instruments, Space Physics Sensor, will monitor the space environment and its effects on microelectronics in the low altitude region as it operates on board the KOMPSAT-1 from 1999 over the maximum of the solar cycle 23. The Space Physics Sensor (SPS) consists of two parts: the Ionospheric Measurement Sensor (IMS) and the High Energy Particle Detector (HEPD). IMS will make in situ Measurements of the thermal electron density and temperature, and is expected to provide a global map of the thermal electron characteristics and the variability according to the solar and geomagnetic activity in the high altitude ionosphere of the KOMPSAT-t orbit. HEPD will measure the fluxes of high energy protons and electrons, monitor the single event upsets caused by these energetic charged particles, and give the information of the total radiation dose received by the spacecraft. The continuous operation of these sensors, along with the ground measurements such as incoherent scatter radars, digital ionosondes and other spacecraft measurements, will enhance our understanding of this important region of practical use for the low earth orbit satellites.

• International Journal of Aeronautical and Space Sciences
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• 제16권1호
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• pp.77-88
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• 2015

The dynamics of relative motion in a perturbed orbital environment are exploited based on Gauss' and Cowell's variational equations. The inertial coordinate frame and relative coordinate frame (Hill frame) are used, and a linear high fidelity model is developed to describe the relative motion. This model takes into account the primary gravitational and atmospheric drag perturbations. Then, this model is used in the design of a navigation, guidance, and control system of a chaser vehicle to approach towards and to depart from a target vehicle in proximity operations. Relative navigation uses an extended Kalman filter based on this relative model to estimate the relative position/velocity of the chaser vehicle with respect to the target vehicle. This filter uses the range and angle measurements of the target relative to the chaser from a simulated LIDAR system. The corresponding measurement models, process noise matrix, and other filter parameters are provided. Numerical simulations are performed to assess the precision of this model with respect to the full nonlinear model. The analyses include the navigation errors and trajectory dispersions.