• Journal of Astronomy and Space Sciences
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• 제19권3호
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• pp.225-230
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• 2002

Synthetic Aperture Radar (SAR) has been used for mapping the surface geomorphology of cloudy planets like Venus as well as the Earth. The cloud-free Mars is also going to be scanned by SAR in order to detect buried water channels and other features under the very shallow subsurface af the ground. According to the 'Mid and Long-term National Space Development Plan' of Korea, SAR satellites, in addition to the EO (Electro-Optical) satellites, are supposed to be developed in the frame of the KOMPSAT (Korean Multi-Purpose Satellite) program. Feasibility of utilizing a SAR payload on KOMPSAT platform has been studied by KARI in collaboration with Astrium U.K. The purpose of the ShR program is Scientific and Civil applications on the Earth. The study showed that KOMPSAT-2 platform can accommodate a small SAR like Astrium’s MicroSAR. In this paper, system aspects of the satellite design are presented, such as mission scenario, operation concept, and capabilities. The spacecraft design is also discussed and conclusion is followed.

• Journal of Astronomy and Space Sciences
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• 제9권2호
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• pp.203-212
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• 1992

인공위성의 자세결정을 위해 3축 magnetometer에 의해 측정된 지구 자기장의 자료와 IGRF 모델(tilted-eccentric dipole 모델)을 사용하였다. 지구자기장 모델으 값들을 계산하여 magnetometer 측정자료들과 비교해 보았고 이것으로부터 두 자세각 $\alpha$ 각과 $\beta$들을 구하였다. 이 두 각들을 이용하여 자세결정에 사용되는 Z 축과 자기장의 수직성분 사이의 실 자세각 $\gamma$ 에 대한 bound $\gamma1$과 $\gamma2$를 계산하여 UoSAT-11, 14, 22의 자세 상태를 알아보았다.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2006년도 추계학술대회 논문집
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• pp.145-148
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• 2006

In order to design a micro-thruster which controls the altitude of a space vehicle for a very long lifetime, the flow field should be analyzed considering the nozzle geometry and the difference between stagnation and environmental pressures and so on. This paper describes the axisymmetric non-reacted computational results which were carried out to understand the basic flow phenomena according to the high nozzle pressure ratio. The area ratio is about 56 and the diameter of a nozzle exit is about 0.46 inch. The Mach cell and waves are predicted well.

• 천문학회보
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• 제46권1호
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• pp.58.4-59
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• 2021

This presentation introduces Korea's SNIPE (Small scale magNespheric and Ionospheric Plasma Experiment) mission, formation flying CubeSat constellation. Observing particles and waves on a single satellite suffers from inherent space-time ambiguity. To observe spatial and temporal variations of the micro-scale plasma structures on the topside ionosphere, four 6U CubeSats (~ 10 kg) will be launched into a polar orbit of the altitude of ~500 km in 2021. The distances of each satellite will be controlled from 10 km to more than 100 km by formation flying algorithm. The SNIPE mission is equipped with identical scientific instruments, solid-state telescope, magnetometer, and Langmuir probe. All the payloads have a high temporal resolution (sampling rates of about 10 Hz). Iridium modules provide an opportunity to upload changes in operational modes when geomagnetic storms occur. SNIPE's observations of the dimensions, occurrence rates, amplitudes, and spatiotemporal evolution of polar cap patches, field-aligned currents (FAC), radiation belt microbursts, and equatorial and mid-latitude plasma blobs and bubbles will determine their significance to the solar wind-magnetosphere-ionosphere interaction and quantify their impact on space weather.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 춘계학술대회 논문집
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• pp.113-119
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• 2007

This article deals mainly with two objectives viz, 1) the potentiality of very high-resolution(VHR) multi-spectral and pan chromatic QuickBird satellite data in resources mapping over moderate resolution satellite data (IRS LISS III) and 2) the advantages of using object oriented classification method of eCognition software in land use and land cover analysis over the ISODATA classification method. These VHR data offers widely acceptable metric characteristics for cartographic updating and increase our ability to map land use in geometric detail and improve accuracy of local scale investigations. This study has been carried out in the Sukkalampatti mini-watershed, which is situated in the Eastern Ghats of Tamil Nadu, India. The eCognition object oriented classification method succeeded in most cases to achieve a high percentage of right land cover class assignment and it showed better results than the ISODATA pixel based one, as far as the discrimination of land cover classes and boundary depiction is concerned.

• 항공우주시스템공학회지
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• 제10권1호
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• pp.86-94
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• 2016

In this paper, position control of focal plane compensation device using piezoelectric actuator is conducted. The forcal plane compensation device installed on earth observation satellite camera compensates micro-vibration from reaction wheels. In this study, four experimental models of the open-loop compensation device are derived using MATLAB system identification toolbox in the input range of 0~50Hz. Subsequently, the PID controller for each model is designed and the performance test of each controller is conducted through MATLAB/Simulink. According to frequency response analysis of the closed-loop compensation device system, the PID controller designed for 38~50Hz input range has enough tracking performance for the whole 0~50Hz input range. The maximum output error is about $1{\mu}m$ for the input range. The simulation results has been verified by the experimental method.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.1018-1020
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• 2003

The costal area where takes up over 32% in domestic teritory is considered as very importantly because it has not only economic facilities such as harbor and an industrial complex but also recreation facilities. Moreover, the tidal flat area has been used as culture ponds and salt farms because this area is occupied by various oceanic species. Also, the tidal flat area has played an important role to purify ocean pollution and maintain an ecosystem. However, the costal ecosystem has seriously threatened by domestic reclamation projects and a large-scale tide embankment during recent 10 years in Korea. This serious problem results in loosing 34%(810$km^2$) of the entire domestic costal area. In this paper, the micro-landform in the tidal flat area, which is called as Garolim bay in Korea, is classified by using Landsat TM images also verified through a filed report. Through the result of this, the tidal flat area is expected to manage efficiently especially through analyzing sediment environment and characteristic of grain size by using satellite images.

• Corrosion Science and Technology
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• 제18권5호
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• pp.182-189
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• 2019

A thin spray coating of inorganic black lithium polysilicate (IBLP) on black anodized AZ31B magnesium alloy was fabricated for better corrosion resistance and thermo-optical properties for thermal control of spacecraft components. The morphology of the specimens with and without IBLP-based spray coating was characterized by SEM-EDS techniques. Impedance and potentiodynamic measurements on the specimens revealed better corrosion resistance for the specimen with a thin coating of lithium polysilicate. This was primarily due to the presence of lithium polysilicate inside the micro-cracks of the black anodized specimen, restricting the diffusion paths for corrosive media. Environmental tests, namely, humidity, thermal cycling, thermo vacuum performance, were used to evaluate the space-worthiness of the coating. The thermo-optical properties of the coating were measured before and after each environmental test to ascertain its stability. The specimen with an IBLP-based spray coating showed enhanced thermo-optical properties, greater than ~0.90. Hence, the proposed coating demonstrated better handling, better corrosion resistance, and space-worthiness during the pre-launch phase owing to its improved thermo-optical properties.

• 항공우주시스템공학회지
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• 제16권5호
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• pp.8-16
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• 2022

이 논문에서는 전천후 한반도 주변 감시를 위한 초소형 합성 개구 레이더 (synthetic aperture radar, SAR) 위성군의 배치를 위한 궤도 제어를 분석한다. 국내에서 개발하고 있는 Small SAR technology experimental project (S-STEP)는 한반도 주변 지역의 평균 재방문 주기를 확보하기 위해 여러 기의 위성이 여러 궤도 평면에 등간격으로 배치한다. 동일한 궤도 평면에 진입하는 여러 기의 위성들은 궤도 상에 등간격으로 분포하기 위해 발사체로부터의 분리 속도와 이온 추력기를 이용하여 궤도를 제어한다. 동일한 궤도 평면 상에 등간격으로 위성을 배치하는 궤도 전개를 위해 순간 추력으로 위성 사이의 표류율 차이를 조절해 위성군의 형상을 형성한다. 이 논문에서는 여러 가지 형태의 위성군을 제시하고 발사 전략에 따른 위성군의 배치 결과를 제시한다. 또한, 위성군을 형성하는 기간을 단축시키는 방법과 한계를 제시한다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.394-396
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• 2007

Radio occultation (RO) technique has been used in planetary science since 1960s. When signal goes through atmosphere, it is refracted due to the gradient of atmospheric refractivity. In 1995, the first low earth orbit (LEO) satellite, MicroLab-1, was launched to conduct RO mission. It receives the signal from global positioning system (GPS) satellites. After MicroLab-1, other RO missions, such as CHAMP, SAC-C, and GRACE, are executed in several years later. In 2006, Taiwan launched six LEO satellites for RO mission. The mission name is Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC). Under some abnormal situations, multipath and strong fluctuation in phase and amplitude of the signal appear in moist troposphere. Therefore, open loop (OL) technique has been applied to replace traditional phase lock loop (PLL) technique. In this paper, we will summarize the retrieval processing procedure and discuss the advantages and disadvantages of OL technique.