• Journal of Space Technology and Applications
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• v.3 no.2
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• pp.118-143
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• 2023

Space is becoming more commercialized. Despite of its delayed start-up, space activities in Korea are attracting more nation-wide supports from both investors and government. May 25, 2023, KSLV II, also called Nuri, successfully transported, and inserted seven satellites to a sun-synchronous orbit of 550 km altitude. However, Starlink has over 4,000 satellites around this altitude for its commercial activities. Hence, it is necessary for us to constantly monitor the collision risks of these satellites against resident space objects including Starlink. Here we report a quantitative research output regarding the conjunctions, particularly between the Nuri satellites and Starlink. Our calculation shows that, on average, three times everyday, the Nuri satellites encounter Starlink within 1 km distance with the probability of collision higher than 1.0E-5. A comparative study with KOMPSAT-5, also called Arirang-5, shows that its distance of closest approach distribution significantly differs from those of Nuri satellites. We also report a quantitative analysis of collision-avoiding maneuver cost of Starlink satellites and a strategy for Korea, being a delayed starter, to speed up to position itself in the space leading countries. We used the AstroOne program for analyses and compared its output with that of Socrates Plus of Celestrak. The two line element data was used for computation.

• Aerospace Engineering and Technology
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• v.10 no.2
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• pp.170-176
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• 2011

This paper analyzes the orbit determination results using azimuth and elevation angle from ground tracking data, which has the standard data interface format, GEOS-C. The ground tracking data is very useful for initial orbit determination after a satellite launch. In this paper, the quality of the measurement data has been investigated using a variety of real tracking passes, compared with the high precision orbit data of KOMPSAT-2. The accumulated tracking data from consecutive satellite-ground passes is processed for orbit determination using least square method. The accuracy of orbit determination result is also presented.

• Journal of Korea Multimedia Society
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• v.25 no.2
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• pp.206-214
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• 2022

The way to measure the extent of damage from floods and droughts is to identify changes in the extent of water systems. In order to effectively grasp this at a glance, satellite images are used. KOMPSAT-5 uses Synthetic Aperture Radar (SAR) to capture images regardless of weather conditions such as clouds and rain. In this paper, various deep learning models are applied to perform semantic segmentation of the water system in this SAR image and the performance is compared. The models used are U-net, V-Net, U2-Net, UNet 3+, PSPNet, Deeplab-V3, Deeplab-V3+ and PAN. In addition, performance comparison was performed when the data was augmented by applying elastic deformation to the existing SAR image dataset. As a result, without data augmentation, U-Net was the best with IoU of 97.25% and pixel accuracy of 98.53%. In case of data augmentation, Deeplab-V3 showed IoU of 95.15% and V-Net showed the best pixel accuracy of 96.86%.

• Korean Journal of Food Science and Technology
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• v.54 no.4
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• pp.377-385
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• 2022

This study examined the dietary fiber content of potato and physicochemical characteristics of potato starch isolated from various cultivars. The total dietary fiber content of the Arirang1ho cultivar was 6.30%, which was higher than that of other cultivars. The amylose content ranged from 36.76-55.75%, with Sooseon having the highest amylose content. Analysis of the degree of amylopectin polymerization revealed that all cultivars had a high proportion of DP (degree of polymerization) 13-24. The phosphate content ranged from 45.90-84.23 mg/100 g, with Arirang1ho having the highest and Eunseon having the lowest phosphate content. The resistant starch content ranged from 58.94-79.87%. Geumseon showed the highest breakdown in the range of 587.45-1,129.72 RVU (rapid viscosity unit). Sooseon had the lowest gelatinization enthalpy value for potato starch in the range of 5.54-7.64 J/g. These results provide basic data for the use of potatoes in industrial applications.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2004.03a
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• pp.487-492
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• 2004

본 연구에서는 인공신경망 기법을 이용하여 산사태 발생원인에 대한 가중치를 구하였다. 여름철 집중호우시 산사태가 많이 발생하는 강원도 강릉시 사천면 사기막리 와 주문진읍 삼교리에 해당한다. 산사태가 발생할 수 있는 요인으로 지형도로부터 경사, 경사방향, 곡률, 수계추출을, 정밀토양도로부터 토질, 모재, 배수, 유효토심, 지형을, 임상도로부터 임상, 경급, 영급, 밀도를, 지질도로부터 암상을, Landsat TM 영상으로부터 토지이용도와 추출하여 격자화 하였으며, 아리랑1호 영상으로부터 선구조를 추출하여 l00m 간격으로 버퍼링 한 후 격자화 하였다. 이렇게 구축된 산사태 발생 위치 및 발생요인 데이터 베이스를 이용하여 인공신경망 기법을 적용하여 산사태 발생 원인에 대한 상대적인 가중치를 구하였다. 인공신경망의 역전파 알고리즘을 이용한 사기막리 지역과 삼교리 지역의 산사태 가중치를 보면 GPS를 이용한 현장조사와 위성영상을 이용한 변화탐지 기법모두의 경우모두와 훈련지역을 실제 산사태 발생 지역과 경사도가 0°인 지역, 실제 산사태 발생 지역과 Frequence ratio를 이용하여 작성한 취약성도에서 산사태 발생이 낮을 것으로 예상되는 지역, Frequence ratio를 이용한 취약성도에서 산사태 발생이 높을 것으로 예상되는 지역 과 낮을 것으로 예상되는 지역의 경우에서도 경사도는 1.5～2.5배정도 높은 상대적 가중치를 나타냈다. 이러한 가중치는 산사태 취약성도를 작성하는데 활용될 수 있다.

• Proceedings of the KSRS Conference
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• 2009.03a
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• pp.155-158
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• 2009

본 논문에서는 DLR(German Aerospace Center)에서 운영하는 TerraSAR-X를 이용하여 2009년 1월 19일 18:28 (Local time) 에 서해 대부도/제부도 및 대부도 남쪽 해안을 촬영한 stripmap mode (Dual-Pol: HH, VV) 화상을 취득하여 향후 고해상도 X-밴드 화상의 활용 방안 및 효용성에 대해 검토해 보았다. 함께 취득된 현장자료와의 비교를 통하여 2010 년에 발사될 예정인 아리랑 5 호의 활용방안을 찾고자 한다. 여기서는, 연안에 설치된 양식시설, 소형 선박 그리고 코너리플렉터에 대해서 해석을 수행하였다. 김 양식시설의 경우, 구조와 설치 각도에 따라 다른 후방산란특성을 보였으며, 같은 시설에 대해서도 HH 편파의 후방산란계수가 VV 보다 2.6 dB 높게 나타났다. 그 이유는 김 양식시설이 TeraSAR-X의 전파전파 방향과 수직하게 되어 후방 산란이 많이 일어나는 반면에, B 지역에 설치된 김 양식시설은 TeraSAR-X의 전파전파방향과 약 45 도 비스듬하게 설치되어 있어, 상대적으로 낮은 후방산란계수를 나타내기 때문이다. 또한 한 변의 길이가 각각 1 m, 0.6 m 인 사각면 삼각 수동 전파반사기 두 개를 제부도 북쪽의 갯벌에 설치하여 TerraSAR-X 의 화상에 나타난 후방산란특성을 분석하였다. TerraSAR-X 의 화상이 X-밴드를 사용하고, 높은 해상도로 인해 power spill이 넓게 분포하는 것을 볼 수 있다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.9
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• pp.923-930
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• 2009

In this paper, we introduce a satellite conceptual design software which can be used for outlining a new satellite as well as for educational purpose. This software consists of three commercial tools: MATLAB, STK(Satellite Tool Kit), and Excel. The management of the design software is done by MATLAB which provides basic calculations, GUI(Graphical User Interface), Excel data base management, and STK control. STK, an orbital simulation software developed by AGI, takes a part of obtaining accurate orbital information of a satellite. Excel, a product of Microsoft, is used for the data base of previous satellites and for the saving place of temporary and final results of the software. The conceptual design of a satellite is to roughly estimate power system and mass. In the power system design, the sizes of solar array and battery are determined. Based on the database of existing satellites, we can estimate the subsystems's mass fraction of a target satellite. Design examples for Kompsat 1 and 2 are suggested for verification of the developed software.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.4
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• pp.259-266
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• 2015

Change detection using the heterogeneous data such as aerial images, aerial LiDAR (Light Detection And Ranging), and satellite images needs to be developed to efficiently monitor the complicating land use change. We approached this problem not relying on the intensity value of the geospatial image, but by using RECC(Relative Edge Cross Correlation) which is based on the edge information over the urban and suburban area. The experiment was carried out for the aerial LiDAR data with high-resolution Kompsat-2 and −3 images. We derived the optimal window size and threshold value for RECC-based change detection, and then we observed the overall change detection accuracy of 80% by comparing the results to the manually acquired reference data.

• Journal of Astronomy and Space Sciences
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• v.14 no.2
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• pp.330-346
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• 1997

Korea Multi-Purpose Satellite I (KOMPSAT-I, the first multi-purpose Korean satellite) will be launched in the third quarter of 1999, which is operated on the sun-synchronous orbit for cartography, ocean color monitoring, and space environment monitoring. The main mission of Electro-Optical Camera(EOC) which is one of KOMPSAT-I sensors is to provide images for the production of scale maps of Korea. EOC collects panchromatic imagery with the ground sample distance of 6.6m at nadir through visible spectral band of 510~730nm. For determining KOMPSAT-I crossing time over Korea, this study examines the diurnal variation of solar and atmospheric variables that can exert a great influence on the EOC imagery. The results are as follows: 1) After 10:30 a.m. at the winter solstice, solar zenith angle is less than $70^{\circ}$ and expected flux of EOC spectral band over land for clear sky is greater than about $2.4mW/cm^2$. 2) For daytime the distribution of cloud cover (clear sky) shows minimum (maximum) at about 11:00 a.m. Although the occurrence frequency of poor visibility by fog decreases from early morning toward noon, its effect on the distribution of clear sky is negligible. From the above examination it is concluded that determining KOMPSAT-I crossing time over Korea between 10:30 and 11:30 a.m. is adequate.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.1
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• pp.1-9
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• 2011

The objective of this paper is to improve the accuracy of the 3D geopositioning extracted from Rational Polynomial Coefficient(RPC) provide in the KOMPSAT-2 metadata files. In this paper, we developed the algorithm to adjust a RFM(Rational Functional Model), and could improve the accuracy of a RFM with this algorithm. Furthermore, when a RFM was adjusted with this algorithm, the effects of the number of GCPs on the accuracy of the adjusted RFM was tested. For accuracy assessment using adjusted RFM, 9 ground control points(GCPs) and 24 check points could be used. Results indicated that the root mean squared errors(RMSEs) of horizontal residual errors calculated 24 check points were 2.20(m). The achieved accuracy of three dimensional object-point determination was 1.72(m) in the X-dimension and 1.37(m) in the Y-dimension and 2.20(m) in the Z-dimension.