• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.207-210
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• 2014

This paper is concerned with the prediction of lift-off acoustic loads for a launch vehicle. Intense acoustic load is generated when a launch vehicle is lifted off, and it can induce vibrations of a launch vehicle which cause damage or malfunction of a launch vehicle and a satellite. Lift-off acoustic loads of NARO are predicted by the modified Eldred's second method and the result is compared with the measured data in flight test. The prediction shows similar peak and shape of spectrum to the test data, but some discrepancy can be observed due to the predicted margin. In order to reduce such discrepancy, the sound pressure levels with four source distribution assumptions are calculated. Also, the surface diffraction effects are considered in the predict ion of lift-off acoustic loads, and the predicted result is more similar to the test data.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1252-1258
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• 2000

Koreasat-3 was successfully launched by an Ariane IV launch vehicle on September 5, 1999. Although the primary purpose of the satellite is to replace Koreasat-l, it also can extend its communication service coverage over the Asia-Pacific region. A spacecraft is subjected to severe dynamic loads during launch period. To verify the safety of spacecraft under the launch environment, dynamic tests should be performed such as sine sweep, acoustic and separation shock tests. This paper presents the launch environment test results of Koreasat-3. A total of 188 acceleration responses was measured and compared with the design requirements of components and spacecraft. Dynamic characteristic change was also investigated by comparing between low-level pre/post vibration results. From the review of test results, it is concluded that Koreasat-3 was designed and manufactured with the margin of safety enough to survive the launch loads of Ariane IV.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.448-451
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• 2008

KARI is developing a satellite launch vehicle that is called KSLV(Korea Space Launch Vehicle)-I. During the flight, launch vehicles are exposed to aerodynamic heating conditions while flying at high Mach numbers in the atmosphere. KARI constructed Aerodynamic Thermal Simulation Facility to simulate aerodynamic heating on the ground. ATSF is a facility that can simulate given temperature profile using about 4,000 halogen heaters on fairing model. Aerodynamic heating profile is got from result of thermal analysis using MINIVER, Thermal Desktop, and SINDA/FLUINT. Aerodynamic heating test of fairing of KSLV-I was done using engineering model of payload fairing and Aerodynamic Thermal Simulation Facility. It was found that thermal analytic results show good agreement with aerodynamic heating test results within 6$^{\circ}$C at fairing inner surface. Also it was confirmed that maximum temperature of fairing nose-cone inner surface during flight is lower than allowable temperature limit.

• Journal of the Korean Society of Systems Engineering
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• v.2 no.1
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• pp.37-41
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• 2006

The KSLV-I satellite launch vehicle will be launched in a space center currently under construction. The Space Center which is an advance post base of space development of Korea is located on Oenaro island in Kohung, South Cholla Province. A Ground Complex of the Space Center consists of an AC(Assembly Complex), a LC(Launch Complex), and a MCC(Mission Control Center). Assembly and test facilities are located in the AC in which stage assembly, integrated assembly, check-up, certification test, and pre-launch test are made effectively. A launch pad, fuel supply facilities, a launch control center and associated supporting facilities are located in the LC, and the MCC has control over the space center. These ground complex facilities have diverse forms of an interface with mechanical device, electric device, and etc. These should also provide optimum condition and performance during launch operation processes of the launch vehicle. This paper introduces the result of R&D for the AC of the ground complex performed during system design period.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.686-689
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• 2006

SAC is earth observation camera being developed by satrec initiative. It provides 10m in multi-spectral channel and 50km swath width at 685km altitude. The EQM of SAC has been developed and tested. In this paper, the procedure and result of the vibration test of SAC to validate structural design and to verify structural toughness are described.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2005.11a
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• pp.117-120
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• 2005

A Digital Broadcasting Satellite (DBS) receiver converts digital A/V streams received from a satellite to analog NTSC A,/V signals in real-time. Multi-tasking is an efficient way to improve the utilization of the processor core in real-time applications. In this paper, we propose a hybrid approach with a balanced trade-off between hardware kernel and multi-tasking programming to increase a system throughput. First, the schedulability of the critical hard real-time tass in the DBS receiver is verified by using a simple feasibility test. Then. several soft real-time tasks are thoughtfully programmed to satisfy functional requirements of the system.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.2
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• pp.55-63
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• 2018

This study analyzed the applications of near real-time drought monitoring using satellite rainfall for the Korean Peninsula and un-gaged basins. We used AWS data of Yongdam-Dam, Hoengseong-Dam in Korea area, the meteorological station of Nakhon Rachasima, Pak chong for test-bed to evaluate the validation and the opportunity for un-gaged basins. In addition, we calculated EDI (Effective doought index) using the stations and co-located PERSIANN-CDR, TRMM (Tropical Rainfall Measurement Mission) TMPA (The TRMM Multisatellite Precipitation Analysis), GPM IMERG (the integrated Multi-satellitE Retrievals for GPM) rainfall data and compared the EDI-based station data with satellite data for applications of drought monitoring. The results showed that the correlation coefficient and the determination coefficient were 0.830 and 0.914 in Yongdam-dam, and 0.689 and 0.835 in Hoengseng-Dam respectively. Also, the correlation coefficient were 0.830, 0.914 from TRMM TMPA datasets and compasion with 0.660, 0.660 based on PERSIANN-CDR and TRMM data in nakhon and pakchong station. Our results were confirmed possibility of near real-time drought monitoring using EDI with daily satellite rainfall for un-gaged basins.

• Journal of the Korean earth science society
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• v.32 no.6
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• pp.560-574
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• 2011

Satellite images that have been obtained periodically and continuously are very effective data to monitor the changes of Earth's surface. Traditionally, the studies on change detection using satellite images have mainly focused on comparison between two results after analyzing two images respectively. However, the interests in researches to catch smooth trends and short duration events from continual multi-temporal images have been increased recently. In this study, we introduce and test an approach based on 3D wavelet transform to analyze the multi-temporal satellite images. 3D wavelet transform can reduce the dimensions of data conserving main trends. Also, it is possible to extract important patterns and to analyze spatial and temporal relations with neighboring pixels using 3D wavelet transform. As a result, 3D wavelet transform is useful to capture the long term trends and short-term events rapidly. In addition, we can expect to get new information through sub-bands of 3D wavelet transform which provide different information by decomposed direction.

• Korean Journal of Remote Sensing
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• v.23 no.5
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• pp.409-420
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• 2007

Since 1988, pine wilt disease has spread over rapidly in Korea. It is not easy to detect the damaged pine trees by pine wilt disease from conventional remote sensing skills. Thus, many possibilities were investigated to detect the damaged pines using various kinds of remote sensing data including high spatial resolution satellite image of 2000/2003 IKONOS and 2005 QuickBird, aerial photos, and digital airborne data, too. Time series of B&W aerial photos at the scale of 1:6,000 were used to validate the results. A local maximum filtering was adapted to determine whether the damaged pines could be detected or not at the tree level from high resolution satellite images, and to locate the damaged trees. Several enhancement methods such as NDVI and image transformations were examined to find out the optimal detection method. Considering the mean crown radius of pine trees, local maximum filter with 3 pixels in radius was adapted to detect the damaged trees on IKONOS image. CIR images of 50 cm resolution were taken by PKNU-3(REDLAKE MS4000) sensor. The simulated CIR images with resolutions of 1 m, 2 m, and 4 m were generated to test the possibility of tree detection both in a stereo and a single mode. In conclusion, in order to detect the pine tree damaged by pine wilt disease at a tree level from satellite image, a spatial resolution might be less than 1 m in a single mode and/or 1 m in a stereo mode.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.1
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• pp.23-35
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• 2023

Korea Augmentation Satellite System (KASS) is a satellite-based augmentation system (SBAS) that provides approach procedure with vertical guidance-I (APV-I) level corrections and integrity information to Korea territory. KASS is used to monitor navigation performance in real-time, and this paper introduces the design, implementation, and verification process of mission monitoring (MIMO) in KASS. MIMO was developed in compliance with the Minimum Operational Performance Standards of the Radio Technical Commission for Aeronautics for Global Positioning System (GPS)/SBAS airborne equipment. In this study, the MIMO system was verified by comparing and analyzing the outputs of reference tools. Additionally, the definition and derivation method of accuracy, integrity, continuity, and availability subject to MIMO were examined. The internal and external interfaces and functions were then designed and implemented. The GPS data pre-processing was minimized during the implementation to evaluate the navigation performance experienced by general users. Subsequently, tests and verification methods were used to compare the obtained results based on reference tools. The test was performed using the KASS dataset, which included GPS and SBAS observations. The decoding performance of the developed MIMO was identical to that of the reference tools. Additionally, the navigation performance was verified by confirming the similarity in trends. As MIMO is a component of KASS used for real-time monitoring of the navigation performance of SBAS, the KASS operator can identify whether an abnormality exists in the navigation performance in real-time. Moreover, the preliminary identification of the abnormal point during the post-processing of data can improve operational efficiency.