• International Journal of Aeronautical and Space Sciences
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• 제6권1호
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• pp.71-76
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• 2005

The KOMPSAT-1 satellite, launched into a circular sun synchronous orbit on Dec. 21, 1999, entered its$6^{th}$year of successful operation this year. The purposes of the mission are to collect earth images (6.6 m resolution), multi-spectral images of the ocean, and to collect information on the particle environment of the low earth orbit. For normal operation, KOMPSAT-1 orbits are determined using GPS navigation solutions. However, at the start of the life of KOMPSAT-1, the 11-year solar activity cycle was at a maximum. Solar flux was maintained at this level until 2002, and thereafter reduced to a moderate level by 2004. Thus, the OD (Orbit Determination) accuracy has varied according to the solar activity. This paper presents the degree to which the OD accuracy could be degraded during a high solar activity period compared with that of a (relatively) low solar activity period. We investigated the effect of the use of solve-for parameters such as a drag coefficient ($C_D$), solar radiation coefficient ($C_R$), and the general accelerations ($G_A$) on OD accuracy with solar activity. For the evaluation of orbit determination accuracy, orbit overlap comparison is used since no independent orbits of comparable accuracy are available for comparison. The effect of the use of a box-wing model instead of a constant cross-sectional area is also investigated.

• 한국대기환경학회지
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• 제15권6호
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• pp.739-746
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• 1999

The spectral aerosol optical thickness of vertical air columns were measured by a ground-based multi-channel sunphotometer at the BAPMoN station(36$^{\circ}$31'N, 126$^{\circ}$19'E) in Anmyon Island, Korea, from 1 March 1998 to 31 May 1998. We used the data of three yellow sand and two clear sky days in order to analyze the temporal variations in aerosol optical thickness at the station. The basic aerosol optical thickness generally represented smaller than 0.3 in a clear sky and the range 0.5 to 1.1 in yellow sand. Especially the aerosol optical thickness represented larger than 0.9 in a heavy yellow sand. It was found that the aerosol optical thickness of yellow sand was highly increased in comparison with the case of a clear sky andparticles larger than 0.5$mu extrm{m}$ were also increased in the spectral distribution of aerosol volume during yellow sand. Consequently the spectral variations in tropospheric aerosol caused by yellow sand were determined by the number concentration of particles larger than 0.5${\mu}{\textrm}{m}$ and the magnitude of yellow sand.

• 대한원격탐사학회지
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• 제14권3호
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• pp.307-314
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• 1998

To examine the detectability of the yellow sand and/or aerosol from China crossing over the Yellow Sea within the range of OSMI wavelengths(400-900 nm), we have investigated the optical characteristics of aerosols in yellow sand events observed on April, 1998 in Seoul. The spectral reflectance(%) and aerosol optical thickness in the range of Visible(VIS) and near Infrared (NIR) wavelengths were derived from the measurements of solar radiation using the GER-2600 spectroradiometer and sunphotometer during the April, 1798. The average spectral reflectance for the yellow sand events is over 40% and higher around 14:30 than 12:00 LST, but that for clear days is about 20% both at 12:00 and 14:30 LST in the range of 500-900 nm. The aerosol optical thickness at 501 nm varied from 0.25 on very clear day to 1.01 during a so-called "yellow-sand" episode and that for 673 nm varied from 0.14 to 0.92, respectively.

• Spatial Information Research
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• 제14권1호
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• pp.85-94
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• 2006

영상융합은 저해상도 다중분광영상과 고해상도 전정영상을 통합시키는 기법으로서 현재 까지 널리 사용되고 있다 하지만, 기존의 사용되어온 방법은 융합과정시 적지않은 분광정보의 왜곡을 불러일으키거나 웨이블렛 기법과 같은 경우 주파수 분해 및 복원 과정이 필요하므로 처리시간이 길어지는 단점이 있다. 본 연구에서는 비교적 간단한 분광정보 보존 기법: 평활화 필터 기반 대체기법을 제안하였다. 이 기법은 단순화 시킨 태양 방사 및 지표면 반사 모델에 기반을 두고 있으며 저주파수 영역 필터링 영상과 전정영상의 해상도 비율을 이용하여 분광학적 특성의 왜곡을 최소화시키며 전정영상의 상세한 지형묘사를 그대로 유지 시킨다. 또한 이 방법은 RGB 의 컬러 합성 뿐만 아니라 단일밴드의 융합에도 적용 시킬 수 있다. 제안된 기법을 검증하기 위하여 IKONOS 전정영상과 다중분광영상을 이용하여 분광정보의 왜곡정도와 공간정보의 상세함에 대한 분석을 하였다. 시각적 검토 및 통계적 방법을 통해 기존의 융합기법과 비교한 결과 분광정보 보전의 측면에서 제안된 SFR 기반 융합기법이 더 나은 결과를 보여주었다.

• 천문학회지
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• 제29권2호
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• pp.223-243
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• 1996

We have constructed a line-by-line model of the A-X system of CO in order to analyze the CO bands appearing in the UV spectra of comets. The model includes electronic, rotational, vibrational transitions, excitations by solar UV radiation, and effects of neutral and electron collisions. The major bands of the A-X system occur in the $1200 - 1800{\AA}$ range where the temporal variation of solar irradiation is significant. The solar spectrum in this spectral range shows many emission lines, which cause a significant Swings effect. We derived fluorescence efficiencies of the bands as functions of heliocentric velocity and cometocentric distance using a high resolution spectrum of the sun. We compared our model with a spectrum of comet P/Halley obtained with the IUE, and estimated that the UV Swings effects are less than 20 fluorescence efficiencies for the most bands of the A-X system. We discuss the temporal variation of solar UV irradiation and its effects on the fluorescence efficiencies. The study of the A-X system also requites knowledge of vibrational and rotational fluorescent processes in the infrared and radio regions because the majority of CO molecules in the coma is in the ground rotational states. The solar infrared spectrum near 5 microns, where the fundamental band of CO occurs, contains strong absorption lines of the fundamental band and hot bands of CO and its isotopes. We derived fluorescence efficiencies of the infrared band as functions of heliocentric velocity and cometrocentric distance. The solar absorption lines near 5 microns cause a 20 reduction of the g-factor of the fundamental band at heliocentric velocities close to 0 km/sec. We discuss the effects of neutral and electron collisions on the fluorescence efficiencies of the infrared and UV bands.

• 태양에너지
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• 제13권2_3호
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• pp.79-90
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• 1993

본 연구에서는 다공성 물질을 이용한 공기용 태양열 집열기(Solar Air Heater)의 설계를 위한 이론적 해석을 하였다. 해석시 필요한 유리 덮개 및 다공성 매질의 파장에 따른 복사특성을 Visible Spectrometer 및 FT-IR로 측정하였다. 다공성 매질로 15 메쉬의 Stainless Steel Wire Screen을 대상으로 하였다. 열전달 현상은 1차원으로 가정하고, 열복사는 Two-Flux Model을 사용하여, 여러 경우의 유량 및 복사 물성치에 대한 집열기 내부에서의 공기온도 및 다공성 매질의 온도를 계산하여 이에 따른 집열기의 효율 등을 계산하였다. 결과로는 무광택 페인트 코팅이 된 경우가 좋은 복사특성을 보였고, 공기유량이 증가할수록, 알베도(Albedo)는 가시광선 영역에서는 작을수록, 적외선 영역에서는 클수록 집열기의 효율은 증가하였다. 다공성 매질의 두께는 0.001m가 적합함을 보였다. 본 연구에서 이는 광학적 두께(Optical Thickness)가 약 1 정도를 의미한다.

• 한국군사과학기술학회지
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• 제13권3호
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• pp.470-477
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• 2010

This paper is a part of developing a program that predicts the surface temperature and the IR images of ground objects by considering solar irradiation and atmospheric convection. The thermal modeling is essential for identifying objects on the scenes obtained from the remote sensing. And the temperature distribution on the objects is necessary to obtain their infrared images in contrast to the background. We considered the composite heat transfer modes including conduction, convection and spectral solar radiation incident on the objects within a scene to calculate the surface temperature distribution. The surface temperatures obtained by using the S/W developed in this study(Silhouette) and a commercial S/W(SE-Workbench-IR) are computed and compared each other. Results obtained by using the S/W developed in this study(Silhouette) show fairly good agreement with those obtained by the SE-Workbench-IR.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.209-212
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• 2001

A flame detector responds either to radiant energy visible to the human eye or outside the range of human vision. Such a detector is sensitive to glowing embers, coals, or flames which radiate energy of sufficient intensity and spectral quality to actuate the alarm. An infra-red detectors can respond to the total IR component of the flame alone or in combination with flame flicker in the frequency range of 5 to 30 Hz. A major problem in the use of infrared detectors receiving total IR radiation is the possible interference of solar radiation in the infrared region. When detectors are located in places shielded from the sun, such as vaults, filtering or shielding the unit from the sun's rays is unnecessary. In this study, we proposed method for redue a false alarm with using filtering & sensor technology for distinguish of causes of raise a false alarm and pure flame.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2003년도 International Symposium on Clean Environment
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• pp.51-54
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• 2003

We analyzed radiative properties of aerosols, $CO^{2}$ and clouds using Optical Properties of Aerosols and Clouds(OPAC) and the Column Radiation Model (CRM). From OPAC, if the soot component is disregarded, dust-like components depict the highest extinction values in the solar spectral range and the lowest. single scattering albedoes, which are attributable to the presence of large particles. In the dust aerosol, the high absorptivity in the infrared may induce a warming of the lower atmospheric layer in the nighttime. The radiative properties of aerosols, clouds and double $CO^{2}$ using the CRM model at Seoul (37N, 127.4 E) on 3 April 2003 were calculated. The solar zenith angle is 65˚ and the surface albedo is 0.1836 during the clear day. The aerosol optical depth change 0.14 to 1.7, which is derived during Asian dust days in Korea. At this time, abedo by aerosols is considered as 0.3. In cloudy condition, the short wave cloud forcing on both the TOA and the surface is -193.89 $Wm^{-2}$ and -195.03 $Wm^{-2}$, respectively, and the long wave cloud forcing is 19.58 $Wm^{-2}$ and 62.08 $Wm^{-2}$, respectively. As a result, the net radiative cloud forcing is -174.31 $Wm^{-2}$ and -132.95 $Wm^{-2}$, respectively. We calculate also radiative heating rates by double $CO^{2}$ during the clear day. The $CO^{2}$ volumn mixing ratio is 3.55E-4.

• 항공우주기술
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• 제7권2호
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• pp.82-87
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• 2008

본 연구에서는 우주에서 가시광 영역으로 지구의 지표면을 고해상도로 촬영하는 위성탑재카메라를 위한 복사에너지 신호량을 모델링하였다. 복사에너지 모델링은 광원으로서의 태양과 지구대기 및 지표면 반사도, 카메라의 특성 등을 포함하며 최종 계산 결과는 광전자카메라의 광검지기에서 생성되는 전자의 수로 나타난다.