• 제목/요약/키워드: Nadir

검색결과 142건 처리시간 0.023초

MANIFESTATIONS OF THE INDIAN OCEAN TSUNAMI OF 2004 IN SATELLITE NADIR-VIEWING RADAR BACKSCATTER VARIATIONS

  • Troitskaya, Yuliya I.;Ermakov, Stanislav A.
    • 대한원격탐사학회:학술대회논문집
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    • 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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    • pp.39-42
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    • 2006
  • The paper reports on the first experimental evidence for space-observed manifestation of the open ocean tsunami in the microwave radar backscatter (in C- and Ku-bands). Significant variations of the radar cross section synchronous with the sea level anomaly were found in the geophysical data record of the altimetry satellite Jason-1 for the track which crossed the head wave of the catastrophic tsunami of 26 December 2004. The simultaneous analysis of the available complementary data provided by the satellite three-channel radiometer enabled us to exclude meteorological factors as possible causes of the observed signal modulation. A possible physical mechanism of modulation of short wind waves due to transformation of the thin boundary layer in the air by a tsunami wave is discussed. The results open new possibilities of monitoring tsunamis from space..

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THE HY-2 RADAR ALTIMETER AND SCATTEROMETER

  • Xu, Ke;Dong, Xiaolong;Zhang, Yunhua;Liu, Heguang
    • 대한원격탐사학회:학술대회논문집
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    • 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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    • pp.135-137
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    • 2006
  • HY-2, the China's satellite for oceanic dynamic environment measurement, is planed to be launched around 2010. The main payloads of HY-2 include a dual-frequency radar altimeter equipped with a three-band nadir-looking radiometer for atmospheric delay correction, a Ku-band radar scatterometer, and a five-band scanning radiometer. This presentation outlines the specifications, parameters, and design of the HY-2 radar altimeter and scatterometer.

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COMS METEOROLOGICAL IMAGER SPACE LOOK SIDE SELECTION ALGORITHM

  • Park, Bong-Kyu;Lee, Sang-Cherl;Yang, Koon-Ho
    • 대한원격탐사학회:학술대회논문집
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    • 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
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    • pp.100-103
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    • 2008
  • COMS(Communication, Ocean and Meteorological Satellite) has multiple payloads; Meteorological Image(MI), Ocean Color Imager(GOCI) and Ka-band communication payloads. MI has 4 IR and 1 visible channel. In order to improve the quality of IR image, two calibration sources are used; black body image and cold space look data. In case of COMS, the space look is performed at 10.4 degree away from the nadir in east/west direction. During space look, SUN or moon intrusions are strictly forbidden, because it would degrade the quality of collected IR channel calibration data. Therefore we shall pay attention to select space look side depending on SUN and moon location. This paper proposes and discusses a simple and complete space look side selection logic based on SUN and moon intrusion event file. Computer simulation has been performed to analyze the performance of the proposed algorithm in term of east/west angular distance between space look position and hazardous intrusion sources; SUN and moon.

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정상 임무운용 상태에서 다목적실용위성 2호 탑재체에 대한 태양 입사각 분석 (SUN INCIDENCE ANGLE ANALYSIS OF KOMPSTAT-2 PAYLOAD DURING NORMAL MISSION OPERATIONS)

  • 김응현;용기력;이상률
    • Journal of Astronomy and Space Sciences
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    • 제17권2호
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    • pp.309-316
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    • 2000
  • KOMPSAT-2 will carry MSC(Multi-Spectral Camera) which provides 1m resolution panchromatic and 4m resolution multi-spectral images at the altitude of 685km sun-synchronous mission orbit. The mission operation of KOMSPAT-2 is to provide the earth observation using MSC with nadir pointing. KOMPSAT-2 will also have the capability of roll/pitch tilt maneuver using reaction wheel of satellite as required. In order to protect MSC from thermal distortion as well as direct sunlight, MSC shall be operated within the constraint of sun incidence angle. It is expected that the sunlight will not violate the constraint of sun incidence angle for normal mission operations without roll/pitch maneuver. However, during roll/pitch tilt operations, optical module of MSC may be damaged by the sunlight. This study analyzed sun incidence angle of payload using KOMPSAT-2 AOCS (Attitude and Orbit Control Subsystem) Design and Performance Analysis Soft ware for KOMPSAT-2 normal mission operations.

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SPOT 위성영상의 대안적 모형화(Alternative model)방법의 비교분석 (Comparison of Alternative Models of the SPOT Imagery)

  • 정원조;김의명;진경혁;유복모;유환희
    • 한국GIS학회:학술대회논문집
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    • 한국GIS학회 2004년도 GIS/RS 공동 춘계학술대회 논문집
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    • pp.559-564
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    • 2004
  • 최근들어 광범위한 지역의 삼차원 국토정보 취득을 위한 고해상도 위성영상의 센서모형화 기법에 관한 연구가 활발히 진행되고 있다. IKONOS나 SPOT 5호와 같은 고해상도 위성영상의 모형화에 앞서 본 연구에서는 각종 응용분야에서 광범위하게 활용되고 있는 SPOT 3호 위성영상을 대상으로 지상기준점을 이용하여 경사촬영(off-nadir viewing)각을 추정하는 기법을 개발하였다. 추정된 경사촬영각은 영상좌표를 보정하는데 사용되었으며 2차원 부등각사상변환을 이용하여 기존의 모형화 방법 보다 간결하고 정확도가 향상된 모형화 기법을 제안하였다. 또한, 기존의 엄밀 센서 모형화 방법을 대체하고 있는 위성영상의 센서모형화를 위한 다양한 방법들이 제안되고 있기 때문에, 2차원 부등각사상변환, 직접선형변환(DLT), 자체검정-DLT(SDLT)등의 추상화된 모형화 방법을 SPOT 위성영상에 대해 기준점 수의 변화에 따라 검사점을 이용하여 수평성분, 수직성분으로 나누어 정확도를 비교 분석하였다.

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A Study on Index of Vegetation Surface Roughness using Multiangular Observation

  • Konda, Asako;Kajiwara, Koji;Honda, Yoshiaki
    • 대한원격탐사학회:학술대회논문집
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    • 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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    • pp.673-678
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    • 2002
  • A satellite remote sensing is useful for vegetation monitoring. But it has some problem. One of these, it is difficult to find a difference of vegetation surface roughness using satellite remote sensing. Each vegetation type has unique surface roughness, for example needle leaves forest, broad leaves forest and grassland. Difference of vegetation surface roughness can be detected by satellite multiangular observation. In this study, objective is to propose index of vegetation surface roughness using BRF property. General vegetation indices are calculated from nadir data of satellite data. A proposed index is calculated from two different observation zenith angle data. Two different zenith data can provide BRF (Bi-directional Reflectance Factor) property of satellite observation data. A proposed index was able to detect different value on where NDVI shows similar high value areas of rice field and forest. This index is useful for vegetation monitoring.

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Forward Mapping of Spaceborne SAR Image Coordinates to Earth Surface

  • Shin, Dong-Seok;Park, Won-Kyu
    • 대한원격탐사학회지
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    • 제18권5호
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    • pp.273-280
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    • 2002
  • This paper describes a mathematical model and its utilization algorithm for calculating the accurate target position on the ellipsoidal earth surface which corresponds to a range-azimuth coordinates of unprocessed synthetic aperture radar (SAR) images. A geometrical model which is a set of coordinate transformations is described. The side-looking directional angle (off-nadir angle) is determined in an iterative fashion by using the model and the accurate slant range which is calculated from the range sampling timing of the instrument. The algorithm can be applied not only for the geolocation of SAR images but also for the high quality SAR image generation by calculating accurate Doppler parameters.

Widely Tunable Coupled-ring Reflector Laser Diode Consisting of Square Ring Resonators

  • Kim, Su-Hyun;Byun, Young-Tae;Kim, Doo-Gun;Dagli, Nadir;Chung, Young-Chul
    • Journal of the Optical Society of Korea
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    • 제14권1호
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    • pp.38-41
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    • 2010
  • We design and fabricate a widely tunable laser diode made of InGaAsP-InP. The diode is monolithically integrated with a wavelength-selective coupled-ring reflector and semiconductor amplifiers. For realization of a compact size device, deeply etched multi-mode interference couplers and square ring resonators composed of total-internal-reflection mirrors are adopted and fabricated using a self-aligned process. It is demonstrated that the laser diode exhibits single mode operation and 16 nm tuning range with side-mode-suppression-ratio exceeding 20 dB.

GROUPS HAVING MANY 2-GENERATED SUBGROUPS IN A GIVEN CLASS

  • Gherbi, Fares;Trabelsi, Nadir
    • 대한수학회보
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    • 제56권2호
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    • pp.365-371
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    • 2019
  • If 𝖃 is a class of groups, denote by F𝖃 the class of groups G such that for every $x{\in}G$, there exists a normal subgroup of finite index H(x) such that ${\langle}x,h{\rangle}{\in}$ 𝖃 for every $h{\in}H(x)$. In this paper, we consider the class F𝖃, when 𝖃 is the class of nilpotent-by-finite, finite-by-nilpotent and periodic-by-nilpotent groups. We will prove that for the above classes 𝖃 we have that a finitely generated hyper-(Abelian-by-finite) group in F𝖃 belongs to 𝖃. As a consequence of these results, we prove that when the nilpotency class of the subgroups (or quotients) of the subgroups ${\langle}x,h{\rangle}$ are bounded by a given positive integer k, then the nilpotency class of the corresponding subgroup (or quotient) of G is bounded by a positive integer c depending only on k.

배란유도주기에 따른 초음파검사와 기초체온표의 비교분석 (A Comparative Analysis of Basal Body Temperature to Ultrasound, as a Method of Ovulation Detection in Induced Ovulatory Menstrual Cycles)

  • 최욱;서병희;이재현
    • Clinical and Experimental Reproductive Medicine
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    • 제12권2호
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    • pp.25-37
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    • 1985
  • Four points on the basal body temperature (B.B.T.) curve was correlated with the estimated time of ovulation, as determined by serial ultrasound in 50 induced menstrual cycles from 22 subjects. The time of ovulation was estimated by measuring the maximal diameter of follicles and observing the morphologic changes within the ovary from follicle to corpus luteum. The results were as following; 1. The diameter of the follicle measured at the day before disappearance was 21.1 mm on an average (S.D.: 2.14). The average follicular growth for 4 days before ovulation was measured at a rate of 2.8 mm/day, and rapid growth of follicle was observed 3.1 mm/day at the day before. 2. The changes associated with rupture of the follicles were the followings, in order of frequency; decrease in size(94%), disappearance of follicles(64%), fluid in the Cul-de-Sac(26%) and increased internal echoes(16%). 3. Only 20 of 50 cycles, exhibited a BBT dip and correlated with the estimated time of ovulation by ultrasound in 2 of which cases(10%). BBT nadir, 30 of 50 cycles, correlated in 5(16.7%). The first day of hyperthermic plateau(FDHP) and BBT coverline was exhibited in all cycles, correlated in 41(82%) and 35(70%) cases. 4. The relationship between the diameter of dominant dominant follicle, measured by ultrasound, and the basal body temperature curve were as following. During cycles in which dip was observed on the BBT curve, the follicular diameter were 10.5${\pm}$2.12 mm on 4 days prior to the point (D-4), and 12.5${\pm}$2.12 mm (D-3), 15.5${\pm$2.12 mm (D-2), 17.0${\pm}$1.41 mm (D-1) and 21.5${\pm}$2.12 mm just prior to the dip (D-0). In the nadir; 9.6${\pm}$1.67 mm (N-4), 12.8${\pm}$1.79 mm (N-3), 16.2${\pm}$1.92 mm (N-2), 18.2${\pm}$2.17 mm (N-1) and 21.4${\pm}$2.61 mm (N-0). In the First day of Hyperthemic Plateau (FDHP); 9.8${\pm}$1.36 mm (F-4), 12.4${\pm}$1.41 mm (F-3),15.1${\pm}$1.57 mm (F-2), 18.1${\pm}$1.67 mm (F-1) and 21.2${\pm}$2.25 mm (F-0). In the BBT coverline endopint; 9.9${\pm}$.39 mm (C-4), 12.5 ${\pm}$1.44 mm (C-3), 15.2${\pm}$1.64 mm (C-2), 18.0 ${\pm}$1.69 mm (C-1), and 21.2${\pm}$2.31 mm (C-0). 5. The relationship between the ultrasonographic signs of ovulation and the basal body temperature curve were as following. The BBT dip correlated with the ovulation in 2 cases, which revealed decrease in follicular diameter (100%), fluid pattem in the Cul-de-Sac (1 case, 50%) and complete disappearance of follicle (1 case, 50%). In the nadir (5 cases); the ultrasonographic signs of ovulation were decrease in follicular diameter (5 cases, 100%), fluid pattern in the Cul-de-Sac (1 case, 20%) and complete disappearance of follicle (3 cases, 60%). In the First day of Hyperthermic Plateau (41 cases); decrease in follicular diameter (40 cases, 97.6%), fluid pattern in the Cul-de-Sac (11 cases, 26.8%), appearance of internal echo and thickening of the wall (6 cases, 14.6%) and com plete disappearance of follicle (28 cases, 68.3%). In the BBT coverline endpoint (35 cases); decrease in follicular diameter (33 cases, 94.3%), fluid pattern in the Cul-de Sac (9 cases, 25.7%), appearance of internal echo and thickening of the wall (5 cases 14.3%) and complete disappearance of follicle (20 cases, 57.1%).

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