• Proceedings of the KSRS Conference
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• 2007.03a
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• pp.257-261
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• 2007

한국 동해 연안의 위성 SAR 영상으로부터 몇가지 흥미로운 현상을 분석하였다. SAR 영상은 위치와 크기에 맞고 해상풍 상태가 $10-12ms^{-1}$ 이하로 원만할 때 와동류，전선，내부파 등의 다른 해양 현상들을 분석할 수 있다. 추후의 연구는 이를 정량적으로 분석하는 것이다. 실측 자료와 맞물리는 SAR 영상은 가시, 적외 복사계 혹은 고도계와 같은 다른 원격탐사 센서의 운용에 지장을 주는 구름이 연구해역에 나타날 때，혹은 육지 오염이 있을 때 등에도 해양, 기상학적 현상에 대한 새롭고 가치있는 정보를 제공할 수 있다.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.728-733
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• 2002

The measurement of river discharge is among the most fundamental observations and is necessary for understanding many water-related issues, such as flooding hazards, sediment transportation, and nutrient movement. Traditionally river discharge is estimated by measuring the water stage and converting the measurement to discharge using a stage-discharge rating curve. The possibility of monitoring river discharge from satellites has been largely ignored, because it is difficult to measure water surface information from space with sufficient precision. In this paper, an efficient approach to discharge estimation using mainly satellite data is developed and described. The proposed method, which focuses on the measurement of water-surface width coupled with river width-stage and stage-discharge relationships, is applied to the Yangtze River with good results.

• Journal of Astronomy and Space Sciences
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• v.5 no.1
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• pp.9-18
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• 1988

Gamma Cassiopeae has been observe at Yonsei University Observatory(YUO) for 31 nights in the period 1983-1987 and a total of 312 UBV observations(104 in each colour) was secured. Light curves of ${\gamma}$ Cas in V, B-V, and U-B have been constructed with the YUO data; among them we present selected light curves of 5 different long nights. Discussed are the general photometric behaviour of ${\gamma}$ Cas, especially in connection with B-V changes, V/R variations of $H\alpha$ and H$\beta$, and high velocity narrow component(hvnc) exhibited in the far UV. Six spectral image sets of $\varepsilon$Per archived on IUE satellite are reduced and their line profiles in C IV and Si IV resonance lines are analyzed to find out any change, but the evidence is unlikely.

• Journal of Astronomy and Space Sciences
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• v.37 no.1
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• pp.29-34
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• 2020

On 21 August 2017, during 16:49 UT and 20:02 UT period, a total solar eclipse started. The totality shadow occurred over the United States in time between ~17:15 UT and ~18:47 UT. When the solar radiation is blocked by the moon, observations of the ionospheric parameters will be important in the space weather community. Fortunately, during this eclipse, two Swarm satellites (A and C) flied at about 445 km through lunar penumbra at local noon of United States in the upper ionosphere. In this work, we investigate the effect of the solar eclipse on electron density, slant total electron content (STEC) and electron temperature using data from Swarm mission over United States. We use calibrated measurements of plasma density and electron temperature. Our results indicate that: (1) the electron density and STEC have a significant depletion associated with the eclipse; which could be due to dominance of dissociative recombination over photoionization caused by the reduction of ionizing extreme ultraviolet (EUV) radiation during the eclipse time (2) the electron temperature decreases, compared with a reference day, by up to ~150 K; which could be due to the decrease in photoelectron heating from reduced photoionization.

• Publications of The Korean Astronomical Society
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• v.19 no.1
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• pp.129-133
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• 2004

In the past, radio astronomers have sought isolation from man-made signals by placing their telescopes in remote locations. These measures may no longer safeguard scientific observations, since NGSO satellite systems, particularly low-Earth orbit (LEO) systems, are usually designed to provide global or wide regional coverage. Further, radio astronomers have historically made their observations in the frequency bands allocated for their use by the member countries of the International Telecommunication Union (ITU). The science of radio astronomy could be adversely impacted by the deployment of large constellations of new non-geostationary orbiting (NGSO) satellites for telecommunications, navigation and Earth observation, and the proliferation of new, high-power broadcasting and telecommunication satellites in geostationary (GSO) orbits. Radio telescopes are extremely sensitive, and, in certain situations, signals from satellites can overwhelm the signals from astronomical sources. This paper describes the problem in detail and identifies ways to mitigate it without adversely affecting the continued vigorous growth of commercial space-based telecommunications.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.69.1-69.1
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• 2010

IC 443 is famous for its interaction with nearby molecular clouds and intense H2 emission lines in infrared. Therefore, it has been studied extensively for the understanding of molecular shocks. We observed H2 mission lines toward the shock-cloud interaction regions of IC 443, known as clumps B, C, and G. The observations were performed with the InfraRed Camera (IRC) onboard a satellite AKARI over 2.5-5.0 um, where previous space observations, e.g. Infrared Space Observatory (ISO) and Spitzer, do not cover. Our AKARI observations provide spectra of sequential pure-rotational and ro-vibrational H2 emission lines. For the clumps C and G, combining with previous mid-infrared observational results, we found that the H2 level populations show a significant separation between v=0 and v=1 levels; v=1 levels are under-populated than v=0 levels, therefore, the population cannot be described by two temperature LTE model, as many people have analyzed for the shocked H2 gas. We also applied the thermal admixture model, dN(H2; T)~T^(-b) dT, with varying ortho-to-para ratios according to the temperature, to describe the level population, and obtained plausible ranges of the H2 gas density and power-law index b.

• Economic and Environmental Geology
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• v.43 no.3
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• pp.249-258
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• 2010

In general, a crustal geomagnetic (or gravity) anomaly compiled at one altitude can be estimated at a different altitude by continuation using the Fourier transform (FT). However, in case of continuation with a great distance between the two elevations, or, in particular, in case of downward continuation, the estimated anomalies by the FT are likely to be mathematically unstable so that the estimated values are not realistic. To solve this problem, two independently measured magnetic field anomalies at different altitudes, such as aeromagnetic and satellite magnetic observations, are implemented to estimate values at in-between altitude for better understanding and interpreting geophysical and geological features. This ‘'dual continuation’' technique is straightforward in the FT and gives a more realistic estimate in all altitudes when we simulated with a set of prismatic bodies at different altitudes. This implies that we add up another constraint like satellite-based observations on the geopotential field modeling for the non-unique geological and geophysical problems to a conventional Fourier-type continuation technique with a single set of observations.

• Ocean and Polar Research
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• v.38 no.4
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• pp.259-270
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• 2016

Sea Surface Salinity (SSS) observations from the Aquarius satellite in the East Sea show large systematic biases mainly caused by the surrounding lands and Radio Frequency Interferences (RFI) along the descending orbits on which the satellite travels from the Asian continent to the East Sea. To develop a technique for correcting the systematic biases unique to the East Sea, the least square regression between in situ observations of salinity and the reanalyzed salinities by HYCOM is first performed. Then monthly mean reanalyzed salinities fitted to the in situ salinities are compared with monthly mean Aquarius salinities to calculate mean biases in $1^{\circ}{\times}1^{\circ}$ boxes. Mean biases in winter (December-March) are found to be considerably larger than those in other seasons possibly caused by the inadequate correction of surface roughness in the sea surrounded by the land, and thus the mean bias corrections are performed using two bias tables. Large negative biases are found in the area near the coast of Japan and in the areas with islands. In the northern East Sea, data sets using the ascending orbit only (SCIA) are chosen for correction because of large RFI errors on the descending orbit (SCID). Resulting mean biases between the reanalysis salinities fitted to in situ observations and the bias corrected Aquarius salinities are less than 0.2 psu in all areas. The corrected mean salinity distributions in March and September demonstrate marked improvements when compared with mean salinities from the World Ocean Atlas (WOA [2005-2012]). In September, salinity distributions based on the corrected Aquarius and on the WOA (2005-2012) show similar distributions of Changjiang Diluted Water (CDW) in the East Sea.

• Journal of the Korean earth science society
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• v.28 no.1
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• pp.123-135
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• 2007

Five episodes of the large-scale transport of air pollutants in East Asia and its inflow into the Korean Peninsula have been analyzed through satellite and ground observations. These episodes include regionally polluted continental airmass, which is created by the pollutants produced in the cities and the industrial regions in China, to land on or pass through the Korean Peninsula by way of the Yellow Sea. The analysis of the NOAA satellite observation data made it possible to create images by combining 3 channels of visible and infrared ray ranges and also to identify the distribution and the transport of the air pollution mass over the Yellow Sea. The ground observation data of the air pollutants gathered in Chongwon were found highly valuable in verifying the information in comparison with ones from the satellite. Especially, regarding the episodes of large-scale transport of the air pollutants, the difference of concentration between $PM_{10}\;and\;PM_{2.5}$ was found small with the increase of $PM_{2.5}$ value. The concentration of $PM_{10}$ in the episode of yellows and, however, was found much higher than that of $PM_{2.5}$. In the episode of 27 January 2006, the inflow of the regionally polluted continental air mass into the central and southwestern region of the Korean Peninsula was observed sequentially in the various ground observatories as well as by the satellite. The north-northwest airflow dissipated the clouds over from Mt. Halla in Jeju Island up to far downwind, reduced air pollution, and created von $K\acute{a}rm\acute{a}n$ vortex.

• Journal of Korea Water Resources Association
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• v.45 no.8
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• pp.755-765
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• 2012

The Land Surface Temperature (LST) is one of the significant factors to understand the water and energy cycles between the land surface and atmosphere. However, few previous studies for spatio-temporal variations of LST has been investigated. In this study, we conducted comparative analyses between the Communication, Ocean and Meteorological Satellite (COMS) and MOderate-Resolution Imaging Spectroradiometer (MODIS) LST data. We compared COMS data with observations to identify the accuracy and found relative underestimated patterns of the COMS data as compared to observations. We also found that COMS LST were underestimated in compare to MODIS LST. The Terra LST was verified to have more similar trends with the COMS LST rather than Aqua LST. While we identified the applicability of COMS based on the results of similar tendencies of two comparisons, more intensive validation research at a variety of field conditions should be conducted to gurantee current COMS LST.