• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.185-185
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• 2000

플라즈마 연구 및 응용에서 플라즈마를 구성하는 이온에 대한 정보를 얻는 것은 중요하다. 특히 플라즈마 진단, 박막 증착, 플라즈마 코팅, 플라즈마 이온주입 등과 같은 플라즈마 프로세싱에서 이온들의 종류 구성비율 및 분포는 매우 중요하다. 질량분석기는 대개 큰 규모로 복잡하고 값비싼 경향이 있다. 플라즈마 교란을 최소화하면서 충분한 질량분해능을 갖고 국소적으로 이온들을 분석할 수 있는 간단하고 작은 규모의 값싼 질량분석기가 필요하다. 본 연구에서는 플라즈마 내에 존재하는 이온을 분석하기 위하여 간단하고 작은 규모의 값싼 프라즈마 이온 질량분석기를 설계, 제작하였다. 이온 질량분석기는 ion extraction part, double focusing sector magnet, ion collector로 구성되어 있다. 플라즈마에 잠기는 ion extraction part의 외부 전극에 Al2O3를 코팅하여 플라즈마 교란을 최소화하였다. 이온들의 공간적 분포를 측정하기 쉽게 하기 위하여 ion extraction part를 이동하여도 질량여과기를 통과한 후에 접속되는 초점의 위치가 Faraday ion collector 에 고정되도록 ion optical system을 설계하였다. Extracting electrode에 의하여 가속된 이온들이 sector magnet에 들어갈 때 평행이 되게 하기 위하여 여러 개의 미세구조를 갖는 Mo grids를 사용하고 immersion lens를 넣어서 이온 광학 시스템을 구성하였다. extraction electrode와 sector magnet 사이에 보조 electrode를 하나 더 넣어서 extracting electrode와 보조 electrode 사이에 immersion lens를 만들었다. 질량여과기로는 permanent magnet sector와 time-varying electrical field를 결합하여 사용하였다. Extracting electrode에 1kV 정도의 전압을 인가하여 이온들을 가속시키고 sector magnet에 톱니파 형태의 전압을 인가하여 mass spectrum을 얻었다. 이온 질량분석기를 플라즈마 장치에 적용하여 질량분해능 등의 특성을 연구하였다. Hot cathode discharge와 inductively coupled RF discharge에서 발생된 질소 플라즈마를 구성하는 이온들의 종류와 그 구성비율을 연구하였다.

• Journal of Astronomy and Space Sciences
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• v.29 no.2
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• pp.233-244
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• 2012

The Korea Astronomy and Space Science Institute and the Department of Astronomy at the University of Texas at Austin are developing a near infrared wide-band high resolution spectrograph, immersion grating infrared spectrometer (IGRINS). The compact white-pupil design of the instrument optics uses seven cryogenic mirrors, including three aspherical off-axis collimators and four flat fold mirrors. In this study, we introduce the optomechanical mount designs of three off-axis collimating mirrors and one flat slit-viewer fold mirror. Two of the off-axis collimators are serving as H and K-band pupil transfer mirrors, and are designed as system alignment compensators in combination with the H2RG focal plane array detectors in each channel. For this reason, the mount designs include tip-tilt and parallel translation adjustment mechanisms to properly perform the precision alignment function. This means that the off-axis mirrors' optomechanical mount designs are among the most sensitive tasks in all IGRINS system hardware. The other flat fold mirror is designed within its very limitedly allowed work space. This slit-viewer fold mirror is mounted with its own version of the six-point kinematic optics mount. The design work consists of a computer-aided 3D modeling and finite element analysis (FEA) technique to optimize the structural stability and the thermal behavior of the mount models. From the structural and thermal FEA studies, we conclude that the four IGRINS mirror mounts are well designed to meet all optical stability tolerances and system thermal requirements.

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.351-353
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• 2017

To realize large-format compact array detectors covering a wide far-infrared wavelength range up to 200 µm, we have been developing Blocked-Impurity-Band (BIB) type Ge detectors with the room-temperature surface-activated wafer bonding technology provided by Mitsubishi Heavy Industries. We fabricated various types of $p^+-i$ junction devices which possessed a BIB-type structure, and evaluated their spectral response curves using a Fourier transform spectrometer. From the Hall effect measurement, we also obtained the physical characteristics of the $p^+$ layers which constituted the $p^+-i$ junction devices. The overall result of our measurement shows that the $p^+-i$ junction devices have a promising applicability as a new far-infrared detector to cover a wavelength range of $100-200{\mu}m$.

• Journal of Korean Society for Geospatial Information Science
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• v.21 no.3
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• pp.63-71
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• 2013

This study calculated vegetation indexes such as SR, NDVI, SAVI, and LAI to figure out correlations regarding vegetation by using high resolution KOMPSAT-2 images and LANDSAT images based on the forest biomass distribution map that utilized field survey data, satellite images and LiDAR data and then analyzed correlations between their values and forest biomass. The analysis results reveal that the vegetation indexes of high resolution KOMPSAT-2 images had higher correlations than those of LANDSAT images and that NDVI recorded high correlations among the vegetation indexes. In addition, the study analyzed the characteristics of hyperspectral images by using the COMIS of STSAT-3 and Hyperion images of a similar sensor, EO-1, and further the usability of biomass estimation in hyperspectral images by comparing vegetation index, which had relatively high correlations with biomass, with the vegetation indexes of LANDSAT with the same GSD conditions.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.190.1-190.1
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• 2012

과학기술위성3호는 170kg의 소형위성으로 2006년 사업을 착수하였으며, 올 2012년 12월에 러시아에서 발사할 예정이다. 주탑재체는 다목적 적외선 영상시스템 (MIRIS, Multi-Purpose IR Imaging System)으로 천문연에서 개발을 담당하였으며 우주관측과 지구관측을 수행한다. 우주관측은 $0.9-2{\mu}m$ 대역을 관측에서 은하면의 근적외선 방출광을 탐사하여 우리은하 고온가스의 기원 및 성간 난류의 물리적 특성을 연구한다. 또한 황도극지방을 추가로 관측하여 적외선 우주배경복사의 기원의 연구에 활용될 것이다. 지구관측은 $3-5{\mu}m$의 파장대역으로 한반도의 재해 및 환경변화의 연구에 활용될 예정이다. 부탑재체는 소형영상분광기 (COMIS, Compact Imaging Spectrometer)로 공주대에서 개발을 하였으며 $0.4-1.05{\mu}m$ 파장대역의 지표면 분광영상의 획득이 주요 임무이다. 소형영상분광기를 위하여 다양한 관측방법 (Strip, Stereo, Slow Skew)을 시도하며, 관측된 분광영상은 수질, 작황, 황사, 근해 환경변화 등 다양한 분야에 활용될 것으로 기대한다. 우주관측임무는 확정되어 주어진 임무기간동안 정해진 일정대로 우주관측을 수행되며, 지구관측임무는 사용자의 요구에 따라 관측지역 및 관측 횟수가 추후에 결정될 것이다. 과학기술위성3호는 기술적으로 기존 과학기술위성 시리즈 보다 향상된 위성체, 탑재체 시스템으로 주어진 우주 및 지구과학 임무를 성공적으로 수행할 것으로 예상되며, 또한 우주 및 지구과학의 연구를 위해 여러 분야에서 활동하는 국내 사용자의 적극적인 참여도 기대하고 있다. 본 발표에서는 다양한 사용자의 관측요청 접수를 위한 지상관제시스템의 설명과 임무관측을 통해 획득된 관측데이터의 전달 방법에 대해 논의한다.

• Korean Journal of Remote Sensing
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• v.26 no.6
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• pp.605-615
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• 2010

This study demonstrates the feasibility of small satellite, namely PROBA platform with the compact high resolution imaging spectrometer (CHRIS), for aerosol retrieval in Hong Kong. The rationale of our technique is to estimate the aerosol reflectances by decomposing the Top of Atmosphere (TOA) reflectances from surface reflectance and Rayleigh path reflectances. For the determination of surface reflectances, the modified Minimum Reflectance Technique (MRT) is used on three winter ortho-rectified CHRIS images: Dec-18-2005, Feb-07-2006, Nov-09-2006. For validation purpose, MRT image was compared with ground based multispectral radiometer measurements and atmospherically corrected Landsat image. Results show good agreements between CHRIS-derived surface reflectance and both by ground measurement data as well as by Landsat image (r>0.84). The Root-Mean-Square Errors (RMSE) at 485, 551 and 660nm are 0.99%, 1.19%, and 1.53%, respectively. For aerosol retrieval, Look Up Tables (LUT) which are aerosol reflectances as a function of various AOT values were calculated by SBDART code with AERONET inversion products. The CHRIS derived Aerosol Optical Thickness (AOT) images were then validated with AERONET sunphotometer measurements and the differences are 0.05~0.11 (error=10~18%) at 440nm wavelength. The errors are relatively small compared to those from the operational moderate resolution imaging spectroradiometer (MODIS) Deep Blue algorithm (within 30%) and MODIS ocean algorithm (within 20%).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.12
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• pp.1013-1020
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• 2020

Spark-induced breakdown spectroscopy (SIBS) utilizes an electric spark to induce a strong plasma for collecting atomic emissions. This study analyses the potential for usinga compact SIBS instead of conventional laser-induced breakdown spectroscopy (LIBS) in discriminating rocks and soils for planetary missions. Targeting bulky solids using SIBS has not been successful in the past, and therefore a series of optimizations of electrode positioning and electrode materials were performed in this work. The limit of detection (LOD) was enhanced up to four times compared to when LIBS was used, showing a change from 78 to 20 ppm from LIBS to SIBS. Because of the higher energy of plasma generated, the signal intensity by SIBS was higher than LIBS in three orders of magnitude with the same spectrometer setup. Changing the electrode material and locating the optimum position of the electrodes were considered for optimizing the current SIBS setup being tested for samples of planetary origin.

• Korean Journal of Remote Sensing
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• v.37 no.4
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• pp.777-788
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• 2021

Since aerosol has a relatively short duration and significant spatial variation, satellite observations become more important for the spatially and temporally continuous quantification of aerosol. However, optical remote sensing has the disadvantage that it cannot detect AOD (Aerosol Optical Depth) for the regions covered by clouds or the regions with extremely high concentrations. Such missing values can increase the data uncertainty in the analyses of the Earth's environment. This paper presents a spatial gap-filling framework using a univariate statistical method such as DCT-PLS (Discrete Cosine Transform-based Penalized Least Square Regression) and FMM (Fast Matching Method) inpainting. We conducted a feasibility test for the hourly AOD product from AHI (Advanced Himawari Imager) between January 1 and December 31, 2019, and compared the accuracy statistics of the two spatial gap-filling methods. When the null-pixel area is not very large (null-pixel ratio < 0.6), the validation statistics of DCT-PLS and FMM techniques showed high accuracy of CC=0.988 (MAE=0.020) and CC=0.980 (MAE=0.028), respectively. Together with the AI-based gap-filling method using extra explanatory variables, the DCT-PLS and FMM techniques can be tested for the low-resolution images from the AMI (Advanced Meteorological Imager) of GK2A (Geostationary Korea Multi-purpose Satellite 2A), GEMS (Geostationary Environment Monitoring Spectrometer) and GOCI2 (Geostationary Ocean Color Imager) of GK2B (Geostationary Korea Multi-purpose Satellite 2B) and the high-resolution images from the CAS500 (Compact Advanced Satellite) series soon.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.90-90
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• 2014

The Immersion Grating Infrared Spectrometer (IGRINS) is the first astronomical spectrograph that uses a silicon immersion grating as its dispersive element. IGRINS fully covers the H and K band atmospheric transmission windows in a single exposure. It is a compact high-resolution cross-dispersion spectrometer whose resolving power R is 40,000. An individual volume phase holographic grating serves as a secondary dispersing element for each of the H and K spectrograph arms. On the 2.7m Harlan J. Smith telescope at the McDonald Observatory, the slit size is $1^{{\prime}{\prime}}{\times}15^{{\prime}{\prime}}$. IGRINS has a plate scale of 0.27" pixel-1 on a $2048{\times}2048$ pixel Teledyne Scientific & Imaging HAWAII-2RG detector with a SIDECAR ASIC cryogenic controller. The instrument includes four subsystems; a calibration unit, an input relay optics module, a slit-viewing camera, and nearly identical H and K spectrograph modules. The use of a silicon immersion grating and a compact white pupil design allows the spectrograph collimated beam size to be 25mm, which permits the entire cryogenic system to be contained in a moderately sized ($0.96m{\times}0.6m{\times}0.38m$) rectangular Dewar. The fabrication and assembly of the optical and mechanical components were completed in 2013. From January to July of this year, we completed the system optical alignment and carried out commissioning observations on three runs to improve the efficiency of the instrument software and hardware. We describe the major design characteristics of the instrument including the system requirements and the technical strategy to meet them. We also present the instrumental performance test results derived from the commissioning runs at the McDonald Observatory.

• Progress in Medical Physics
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• v.28 no.4
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• pp.226-231
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• 2017

The aim is to investigate the spectra responsibilities of QD (Quantum Dot) for the innovation of new dosimetry application for therapeutic Megavoltage X-ray range. The unique electrical and optical properties of QD are expected to make it a good sensing material for dosimeter. This study shows the spectra responsibility of toluene based ZnCd QD and PPO (2.5-diphenyloxazol) mixed liquid scintillator. The QDs of 4 sizes corresponding to an emission wavelength (ZnCdSe/ZnS:$440{\pm}5nm$, ZnCdSeS:470, 500, $570{\pm}5nm$) were utilized. A liquid scintillator for control sample was made of toluene, PPO. The Composition of QD loaded scintillators are about 99 wt% Toluene as solvent, 1 wt% of PPO as primary scintillator and 0.05, 0.1, 0.2 and 0.4 wt% of QDs as solute. For the spectra responsibility of QD scintillation, they were irradiated for 30 second with 6 MV beam from a LINAC ($Infinity^{TM}$, Elekta). With the guidance of 1.0 mm core diameter optical fiber, scintillation spectrums were measured by a compact CCD spectrometer which could measure 200~1,000 nm wavelength range (CCS200, Thorlabs). We measured the spectra responsibilities of QD loaded organic liquid scintillators in two scintillation mechanisms. First was the direct transfer and second was using wave shifter. The emission peaks from the direct transfer were measured to be much smaller luminescent intensity than based on the wavelength shift from the PPO to QDs. The emission peak was shifted from PPO emission wavelength 380 nm to each emission wavelength of loaded QD. In both mechanisms, 500 nm QD loaded samples were observed to radiate in the highest luminescence intensity. We observed the spectra responsibility of QD doped toluene based liquid scintillator in order to innovate QD dosimetry applicator. The liquid scintillator loading 0.2 wt% of 500 nm emission wavelength QD has most superior responsibility at 6 MV photon beam. In this study we observed the spectra responsibilities for therapeutic X-ray range. It would be the first step of innovating new radiation dosimetric methods for radiation treatment.