• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.3
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• pp.439-445
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• 2008

In this paper, the preliminary EMC analysis process between the Communication, Ocean and Meteorological Satellite (COMS) and Geostationary Earth Orbit (GEO) launch vehicles in the frequency range [1MHz-47MHz] is described. The considered launch vehicles are arian V, sea Launch, land Launch, atlas III&V, delta IV, proton M/breeze M, soyuz, HII-A and Angara. The launch vehicle Radiated Emission (RE) specifications have been compared to COMS satellite Radiated Susceptibility (RS) limits. The COMS RS limits are the RS qualification levels of COMS units during launch. As a result, The radiated emission levels of arian V, sea launch, atlas III&V, delta IV, proton M/breeze M, HII-A and angara are compliant with COMS RS limits. The negative margins appear between land launch or soyuz launch vehicle RE and COMS RS. Then, if the land launch or soyuz is chosen by the customer, The tests should be performed at satellite level in order to demonstrate the compatibility with respect to launch vehicles specifications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4B
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• pp.331-337
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• 2002

In this paper we propose extended Kalman filter (EKF)-trilateration method which associates EKF to conventional radiolocation technique, trilateration in order to improve the accuracy of dynamic orbit determination of geostationary satellite for broadcasting of highly accurate Standard Time/Frequency Signal (STFS). We then compare to analyze the time accuracies of three techniques which are differential mode, trilateration locating one of four calibrated earth stations on a neighboring country, and domestic-only baseline EKF-trilateration. Computer simulations have shown that in spite of domestic-only baseline EKF-trilateration of poor GDOP, it is possible to track and locate satellite with an accuracy of a few hundred meter which is the performance 10 times more accurate than trilateration can provide. Finally we can provide standard time service with the time accuracy better than a few ns (frequency stability : 10$\^$-14/ over 7 days) all around Korea peninsula.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.1
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• pp.12-17
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• 2018

This study describes the design and implementation of Antenna for Digital Satellite Communication. The Antenna unit for SHF band consists of Reflector, Septom Polarizer, Feed Horn and Support Frame etc. Thought analysis of space environment before production, the possibility of the malfunction of equipment minimized and we designed a reliable Antenna through simulation for vibration and thermal analysis generated during the launch, and compared pre-simulation of main performance results to test results about main performances of Antenna after production. After fabricating the antenna, the maximum gain of the antenna main beam is 36.5dBi, which satisfies the requirement of 35dBi or more, and it also satisfies the requirement of -20dB for return loss of less than -24dB. Also, the isolation of the transmission and reception of the antenna is -22.6dB or less, which satisfies the requirement of -20dB or less. The antenna for digital satellite communication described in this paper can be used in the satellite field of geostationary earth orbit and low earth orbit requiring high reliability in the future.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.53-56
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• 2001

In this paper we discuss a direct satellite broadcasting system for vehicle. The proposed satellite-steering algorithm and controller based on it are designed for a communication and broadcasting system which uses the Mugungwha satellite. The Mugungwha satellite that the proposed system should steer is a geostationary orbit device. The satellite-steering algorithm computes azimuth and elevation with reference to a stationary point on earth. This is extended to a real satellite steering algorithm that considers position and attitude. Real moving position and attitude are represented by latitude, longitude, roll, pitch and yaw. To apply these five pieces of information to the reference satellite steering algorithm, we introduce Euler's degree coordinates that express independently the rotation of each axis relative to an axis. There are two ways a basic algorithm of the antenna of a vehicle can track and orient to satellite. One way is a feedback loop method for broadcasting gain, while the other is a feedback loop method for position and attitude of a vehicle. In the present paper, we design a controller of satellite broadcasting system for a vehicle using an algorithm that combines the two methods. We performed a simulation and experiment to prove effectiveness.

• Korean Journal of Remote Sensing
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• v.35 no.1
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• pp.83-92
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• 2019

Land cover (LC) is an important factor in socioeconomic and environmental studies. According to various studies, a number of LC maps, including global land cover (GLC) datasets, are made using polar orbit satellite data. Due to the insufficiencies of reference datasets in Northeast Asia, several LC maps display discrepancies in that region. In this paper, we performed a feasibility assessment of LC mapping using Geostationary Ocean Color Imager (GOCI) data over Northeast Asia. To produce the LC map, the GOCI normalized difference vegetation index (NDVI) was used as an input dataset and a level-2 LC map of South Korea was used as a reference dataset to evaluate the LC map. In this paper, 7 LC types(urban, croplands, forest, grasslands, wetlands, barren, and water) were defined to reflect Northeast Asian LC. The LC map was produced via principal component analysis (PCA) with K-means clustering, and a sensitivity analysis was performed. The overall accuracy was calculated to be 77.94%. Furthermore, to assess the accuracy of the LC map not only in South Korea but also in Northeast Asia, 6 GLC datasets (IGBP, UMD, GLC2000, GlobCover2009, MCD12Q1, GlobeLand30) were used as comparison datasets. The accuracy scores for the 6 GLC datasets were calculated to be 59.41%, 56.82%, 60.97%, 51.71%, 70.24%, and 72.80%, respectively. Therefore, the first attempt to produce the LC map using geostationary satellite data is considered to be acceptable.

• Korean Journal of Remote Sensing
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• v.37 no.5_1
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• pp.861-870
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• 2021

In this study, fused Aerosol Optical Depth (AOD) data were produced using AOD products from the Geostationary Ocean Color Imager (GOCI) onboard Communication, Oceanography and Meteorology Satellite (COMS)satellite and the Advanced Himawari Imager (AHI) onboard Himawari-8. Since the spatial resolution and the coordinate system between the satellite sensors are different, a preprocessing was first preceded. After that, using the level 1.5 AOD dataset of AErosol RObotic NETwork (AERONET), which is ground-based observation, correlations and trends between each satellite AOD and AERONET AOD were utilized to produce more accurate satellite AOD data than the originalsatellite AODs. The fused AOD were found to be more accurate than the originalsatellite AODs. Root Mean Square Error (RMSE) and mean bias of the fused AODs were calculated to be 0.13 and 0.05, respectively. We also compared errors of the fused AODs against those of the original GOCI AOD (RMSE: 0.15, mean bias: 0.11) and the original AHI AOD (RMSE: 0.15, mean bias: 0.05). It was confirmed that the fused AODs have betterspatial coverage than the original AODsin areas where there are no observations due to the presence of cloud from a single satellite.

• Journal of Satellite, Information and Communications
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• v.11 no.4
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• pp.74-80
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• 2016

In this paper, the modeling and implementation results of the operational test and evaluation tool of the KASS up-link station composed of the GEO(Geostationary Earth Orbit) satellite signal analysis tool model that analyzes the GEO satellite signal and the GEO message analysis tool model that analyzes the GEO satellite navigation message. In addition, we describe the results of software modeling and implementation of some software models of GEO satellite and KASS up-link stations that can generate and provide simulated signals to operational test and evaluation tools of these KASS up-link stations.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1403-1405
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• 2008

In this paper, the preliminary EMC analysis process between the Communication, Ocean and Meteorological Satellite (COMS) and Geostationary Earth Orbit (GEO) launch vehicles in the frequency range [1MHz-47MHz] is described. The considered launch vehicle is the Arian V. The launch vehicle Radiated Emission (RE) specifications have been compared to COMS satellite Radiated Susceptibility (RS) limits. The COMS RS limits are the RS qualification levels of COMS units during launch. As a result, The radiated emission levels of the Arian V is compliant with COMS RS limits.

• Journal of Astronomy and Space Sciences
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• v.14 no.1
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• pp.142-149
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• 1997

This paper applied one of the well-known optimal control theory, namely, linear quadratic regulator(LQR), to the station-keeping maneuvers(SKM) for a geostationary satellite. The boundary conditions to transfer the system with a good accuracy at a terminal time were based upon the predicted orbital data which are created due to the Earth's non-uniform mass distribution's effect during 14 days and due to luni-solar effect during 28 days. Through the linearization of the nonlinear system equation with respect to reference orbit and the numerical integration of Riccati equation, the optimal trajectories and the corresponding control law have been obtained by using LQR. From the comparison of ${\Delta}V$ obtained by LQR with the ${\Delta}V$ obtained anatically by geometric method, Station Keeping Maneuvers(SKM) via LQR may provide comparable results to a real system. Furthermore it will demonstrate the possibility in fuel optimization and life extension of geostationary satellite.

• Journal of Satellite, Information and Communications
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• v.4 no.2
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• pp.20-27
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• 2009

In this paper, HAPS operation scenario is proposed to minimize the interference from HAPS user terminal(HUT) to geostationary earth orbit(GEO) satellite receiver. The conventional scenario has been assumed for fully operated situation of HUT. However, all the HUTs could not be fully operated in a real system operation. Therefore, in order to reduce the interference to other systems, multibeam operation scenarios such as time division and adaptive time division methods are proposed and the interference effect of HUT to satellite receiver is evaluated according to various operation rate of HUT.