• Journal of Advanced Navigation Technology
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• v.23 no.3
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• pp.237-244
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• 2019

Since SBAS provides users with GNSS orbit, clock, and ionospheric corrections and integrity, the more precise positioning is possible. As the SBAS service area is expanded due to the development of the SBAS and the installation of the additional ground stations, there is a region where two or more SBAS messages can be received. However, the research on multi-constellation SBAS selection method has not carried out. In this study, we compared the result of positioning accuracy after applying the SBAS correction selected by using WAAS priority, EGNOS priority, or error covariance comparison method to LEO satellites in the regions where WAAS and EGNOS signals are transmitted simultaneously. When using WAAS priority method, 3D orbit error is smallest at 2.57 m. The covariance comparison method is outperform at the center of the overlap region far from each WAAS and EGNOS stations. In the eastern region near the EGNOS stations, the 3D orbit errors using EGNOS priority method is 8% smaller than the errors using the WAAS priority method.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.45-56
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• 1999

There have been many coal mines abandoned since late 1980s in Korea. Due to the abandoned mines, there have been ground subsidences in some area where are under ground reinforcement works now. So, this study shows the general phenomena of mining subsidence and the procedure of ground reinforcement. In general the procedure for ground reinforcement is as below, 1) obtaining information from inquiries and observations, 2) satellite image analysis and surface geological mapping, 3) analysis of maps of coal mines, 4) geophysical survey and boring test and 5) selection of reinforcement method. The case of reinforcement design at Chul-am area, Kangwon Province is introduced in this article.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.419-422
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• 2004

This paper was carried out desertification area change detection from 1980s to 2000s per unit decade using by multitemporal satellite images (Landsat MSS, TM, ETM+). This study aims to use Spectral Mixture Analysis (SMA) to identify and classify study area. Endmembers is selected bare soil, green vegetation (GV), water body using by Minimum Noise Fraction (MNF). Endmembers used to generate increase and decrease images respective from 1980s to 1990s and from 1990s to 2000s. From the analysis of multitemporal change detection for three periods, it was apparent that the area of bare soil increased significantly, with simultaneous decrease of GV and water body. The multitemporal fraction images can be effectively used for change detection. Though there is no field survey dataset, SMA is reliable result of change detection in desertification in China.

• Proceedings of the KSRS Conference
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• v.1
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• pp.290-293
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• 2006

COMS (Communication, Ocean and Meteorological Satellite) shall be operated with two remote sensing payloads, MI (Meteorological Imager) and GOCI (Geostationary Ocean Color Imager). Since both payloads have rotating mechanisms, the dynamic coupling between two payloads is very important considering the pointing stability during GOCI operation. In addition, COMS adopts a single solar wing to improve the image quality, which leads to the unbalanced solar pressure torque in COMS. As a result, the off-loading of the wheel momentum needs to be performed regularly (2 times per day). Since the frequent off-loading could affect MI/GOCI imaging performance, another suboptimal off-loading time needs to be considered to meet the AOCS design requirements of COMS while having margin enough in the number of thruster actuations. In this paper, preliminary analysis results on the pointing stability and the wheel off-loading time selection with respect to MI/GOCI operations are presented.

• Proceedings of the KSRS Conference
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• v.1
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• pp.191-195
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• 2006

This paper discusses wheel offloading approaches of COMS which has a single side solar array system for the accommodation of the optical payloads. First of all, in an effort to reduce fuel consumption and reflect practical implementation point of view, thruster sets for wheel offloading are proposed based on numerical analyses taking into account the COMS configuration. In this analysis, it is assumed that the wheel offloading is conducted twice a day. Secondly, in order to evaluate the effectiveness of the proposed thruster sets, orbit simulations have been conducted for several wheel offloading approaches and compared.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.874-880
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• 2003

Many mechanical systems are over-constrained if only rigid bodies are used to model the system. One example of such system is a satellite system with solar panels. To avoid this over-constrained problem, solar panels can be modeled as flexible bodies. The CMS(Component Mode Synthesis) method is widely used to analyze the flexible multi-body system because it can considerably approximate the deformation of the flexible bodies using small number of well-selected mode. However, it is very difficult to decide the boundary condition and the selection of modes. In this paper, the methods for mode synthesis and setting the boundary condition are presented to analyze the flexible multi-body system with over-constraints. Finally, the reliability of proposed method is verified by solar panel's deployment test.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.802-805
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• 2003

Structural surface becomes an antenna. The integration of antennas into structural body panels is a new high payoff technology. It emerged from the need to improve structural efficiency and antenna performance. In this paper, we developed new design concept for the structural surface which transmits and receives the electromagnetic signals, and it is termed Surface-Antenna-Structure (SAS). Design procedure was presented including structure design. material selection and design of antenna elements, which was processed according to the communication with KORSAT satellite at Ku-Band (12.25-12.75 GHz). The final demonstration article was 350$\times$200$\times$7.5mm flat antenna panel. Experimental results for antenna performances were in good agreements with design requirements. Also structural analysis was performed with SAS. estimating stress distributions under simply supported condition with Laminated Plate Theories and Wavier Solutions. The SAS concept can be extended to give a useful guide to manufacturers of structural body panels as well as antenna designers. promising innovative future communication technology.

• Journal of Environmental Impact Assessment
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• v.20 no.5
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• pp.697-703
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• 2011

The purpose of this study aims to preserve biodiversity in increasingly fragmented green patches for spatial analysis of planting on the eco-corridors and to optimize the target species, the location, width, cross section of the eco-corridors. It was suggested that eco-corridors should have to planned at early stages of road planning so that the number and locations of eco-corridors in advance. Ecological corridor is the facility to connect two habitats fragmented by road, dam, housing and industrial area. And, everyone agree that ecological corridor is important useful structural component that help animal movement in fragmented landscapes. However, ecological corridors have many problems of the recorded the size of corridor, planting species to nearby exiting vegetation species and structure. The most important facts that there are no consideration for location of animal migration and behavior using eco-corridors. This study was carried out to spatial analysis of eco-corridors location, satellite data and GIS were used to analyze for searching optimum location of the eco-corridors.

• Journal of Aerospace System Engineering
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• v.8 no.1
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• pp.36-41
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• 2014

KAFASAT is a CubeSat which has a high level mission of testing the possibility of establishing the LEO satellite constellation providing the role of communication nodes and quasi-realtime image recognition of battlefield in accordance with the aspect of future-war-environment. The high level mission is developed using the Pugh selection method, which is one of system engineering tools. In order to accomplish the high level mission objectives and deduce engineering level requirements, system engineering tools such as Analytic Hierarchy Process and Quality Function Deployment are used. The subsystem synthesis in the context of system engineering process is done using a developed integrated design environment. The paper also includes the conceptual design results of the KAFASAT, which can be used as a baseline for upcoming preliminary design.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.422-427
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• 2001

The component mode synthesis method allows the elastic deformation of each component in the flexible multibody system by a sum of modes and modal coordinates. This paper focuses on the selection of boundary conditions and deformation modes for redundantly constrained flexible components in mechanical system dynamics. The result of a flexible body dynamic analysis with only normal modes is used to identify proper boundary conditions of a static modes and a desired set of static modes which will be used in the final model. A simple four bar mechanism is used to explain the procedure and a space satellite with solar panels is analyzed using the proposed method.