• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.1
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• pp.172-180
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• 2017

Korean army has been trying to construct a future tactical network in collaboration with TICN at the ground level and the next-generation military satellite system in the space level. However, due to the low bandwidth and high operational cost, the satellite system has the limitation to exchange all kind of tactical information through it. To overcome the limitation, there have been several researches to construct airborne networks. In this paper, we propose an effective interworking architecture and operation scheme between terrestrial tactical networks and aerial relay networks to counteract against the communication breaks of terrestrial terminals. And, we also propose a way to analyze its effectiveness. The experimental results show that the interworking of aerial relay networks can manage the failure situations in terrestrial tactical networks very effectively.

• Journal of Aerospace System Engineering
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• v.12 no.5
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• pp.76-88
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• 2018

Space agencies such as NASA, ESA, and the US military provide guidelines and standards for PA(product assurance) requirements and plans. In recent years, major satellite manufacturers around the world have been mitigating PA requirements and processes by tailoring. PA tailoring has been implemented to improve the cost and schedule efficiency. PA tailoring can be accomplished based on various factors such as mission, classification of mission risk, complexity, development cost, life cycle, etc. In this study, PA tasks according to the mission risk classification proposed by NASA are investigated, and the tailoring method is suggested for the optimization of the development cost and schedule. In particular, the classification of mission risk for the satellites under development or operation in Korea is performed, and PA characteristics in accordance with mission risk are analyzed.

• Journal of IKEEE
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• v.24 no.1
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• pp.72-80
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• 2020

This paper describes the design and fabrication of a BUC(Block Up-converter) which is a component of a FST (Flyaway Satellite Terminal), one of the ET(Earth Terminal) of the military satellite. BUC is physically composed of an up-converter module, a high power amplifier module, a receive band suppression filter, a housing, and a cable assembly. It was designed using simulator AWR to satisfy the electrical characteristics of BUC's such as maximum output power, gain, unwanted signal, and intermodulation. The maximum output power and gain characteristics were measured at 43.4dBm and 51.8dB, respectively. The unwanted wave and intermodulation characteristics were -73.5dBc and -31.9dBc, respectively. Of the electrical requirements of Table 1, not only the above four but also all of the items were confirmed to be satisfied.

• Journal of IKEEE
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• v.24 no.1
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• pp.81-89
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• 2020

This paper describes the design and fabrication of a LNB(Low Noise Block downd-converter) which is a component of a FST(Flyaway Satellite Terminal), one of the ET(Earth Terminal) of the military satellite. LNB is physically composed of an down-converter module, a low noise amplifier module, a transmit band suppression filter, a isolator, a housing, and a cable assembly. It was designed using simulator (AWR) to satisfy the electrical characteristics of LNB's such as gain, noise figure and unwanted signal. The gain and noise figure characteristics were measured at 61.4dBm and 1.37dB, respectively. The unwanted wave was measured at -66.79dBc. Of the electrical requirements of Table 1, not only the above three but also all other items were confirmed to be satisfied.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.11
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• pp.1031-1041
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• 2014

In this paper, we propose a traffic load control scheme, called fast congestion control (FCC), for a satellite channel using enhanced random access schemes. The packet repetition used by enhanced random access schemes increases not only the maximum throughput but also the sensitivity to traffic load. FCC controls traffic load by using an access probability, and estimates backlogged traffic load. If the backlogged traffic load exceeds the traffic load corresponding to the maximum throughput, FCC recognizes congestion state, and processes the backlogged traffic first. The new traffic created during the congestion state accesses the channel after the end of congestion state. During the congestion state, FCC guarantees fast transmission of the backlogged traffic. Therefore, FCC is very suitable for the military traffic which has to be transmit urgently. We simulate FCC and other traffic load control schemes, and validate the superiority of FCC in latency.

• Korean Journal of Remote Sensing
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• v.17 no.3
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• pp.275-284
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• 2001

This study was carried out to evaluate high resolution satellite imagery of IKONOS for classifying the land cover, especially forest type. The IKONOS imagery of 11km$\times$11km size was taken on April 24, 2000 in Bong-pyoung Myun Pyungchang-Gun, Kangwon Province. Land cover classes were water, coniferous evergreen, Larix leptolepis, broad-leaved tree, bare land, farm land, grassland, sandy soil and asphalted area. Supervised classification method with algorithm of maximum likelihood was applied for classification. The terrestrial survey was also carried out to collect the reference data in this area. The accuracy of the classification was analyzed with the items of overall accuracy, producer's accuracy, user's accuracy and k for test area through the error matrix. In the accuracy analysis of the test area, overall accuracy was 94.3%, producer's accuracy was 77.0-99.9%, user's accuracy was 71.9-100% and k and 0.93. Classes of bare land, sandy soil and farm land were less clear than other classes, whereas classification result of IKONOS in forest area showed higher performance than that of other resolution(5-30m) satellite data.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.291-291
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• 2022

북한의 황강댐은 우리나라와 북한이 공유하고 있는 대표적인 하천인 임진강 상류에 존재하는 댐으로서 팔당댐의 약 1.5배의 규모를 가지고 있으며, 하류로의 발전방류와 함께 유역 외 지역인 예성강 지역으로 방류량의 일부를 도수시키며 이를 통해 예성강 1, 2호 발전소에서의 발전을 실시하고, 생활, 공업, 농업용수를 예성강 유역에 공급하는 것으로 파악된다. 2009년 9월 6일 임진강 상류 황강댐에서의 대규모 방류로 인해 경기도 연천군 일대에 홍수가 발생하였으며 이로 인한 인명 및 재산피해가 발생한 바 있다. 이에 우리나라에서는 임진강 하류에 군남홍수조절지를 설치하고 상류의 필승교 수위표를 이용하여 홍수경보체제를 운용하고 레이더 강우와 수문모형을 이용한 감시체계를 유지하고 있으나 황강댐 운영현황이 불확실함에 따라 정확한 예보가 어려운 실정이다. 본 연구에서 미계측 지역의 홍수예보를 위해 산정한 상당상수량이란 저수지의 현재 수위로부터 특정 수위까지 도달하는데 요구되는 강우량을 말하며 강우예보 시점에서 저수지의 최대 수위를 신속하게 파악할 수 있는 홍수예경보 수단이다. 미계측 유역인 임진강 상류 황강댐 유역의 상당강우량을 산정하기 위해 인공위성영상에서 획득한 댐 수위의 시계열 자료를 활용하여 간접적으로 보정된 황강댐 상류의 수문모형을 이용하였으며 현재 댐 수위로부터 주요 수위(방류개시수위, 상시만수위, 계획홍수위)에 도달하게 되는 상당강우량을 산정하였다.

• Korean Journal of Remote Sensing
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• v.25 no.4
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• pp.311-320
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• 2009

This study was carried out to estimate forest biomass and to produce forest biomass thematic map for Muju county by combining field data from the 5$^{th}$ National Forest Inventory (2006-2007) and satellite data. For estimating forest biomass, two methods were examined using a Landsat TM-5(taken on April 28th, 2005) and field data: multi-variant regression modeling and t-Nearest Neighbor (k-NN) technique. Estimates of forest biomass by the two methods were compared by a cross-validation technique. The results showed that the two methods provide comparatively accurate estimation with similar RMSE (63.75$\sim$67.26ton/ha) and mean bias ($\pm$1ton/ha). However, it is concluded that the k-NN method for estimating forest biomass is superior in terms of estimation efficiency to the regression model. The total forest biomass of the study site is estimated 8.4 million ton, or 149 ton/ha by the k-NN technique.

• Journal of the Korean earth science society
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• v.40 no.2
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• pp.119-134
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• 2019

In order to analyze the observational environment of solar radiation stations operated by the Korea Meteorological Administration (KMA), we used the digital elevation model (DEM) and the solar radiation model to calculate a topographical shading, sky view factor (SVF) and solar radiation by surrounding terrain. The sky line and SVF were calculated using high resolution DEM around 25 km of the solar stations. We analyzed the topographic effect by analyzing overlapped solar map with sky line. Particularly, Incheon station has low SVF whereas Cheongsong and Chupungryong station have high SVF. In order to validation the contribution of topographic effect, the solar radiation calculated using GWNU solar radiation model according to the sky line and SVF under the same meteorological conditions. As a result, direct, diffuse and global solar radiation were decreased by 12.0, 5.6, and 4.7% compared to plane surface on Cheongsong station. The 6 stations were decreased amount of mean daily solar radiation to the annual solar radiation. Among 42 stations, eight stations were analyzed as the urgent transfer stations or moving equipment quickly and more than half of stations (24) were required to review the observational environment. Since the DEM data do not include artifacts and vegetation around the station, the stations need a detail survey of observational environment.

• Journal of Aerospace System Engineering
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• v.16 no.4
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• pp.28-34
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• 2022

In 2021, Virgin Orbit converted a 747-400 aircraft into an air launch platform, and successfully launched it twice in February and July. Compared to the existing ground launch, interest in the air launch is increasing due to its great utility, such as its independence from the launch location or weather, cost reducing factor, shorter launch preparation time, and its benefit pursuant to altitude and speed. Additionally, as small satellites have similar performance to mid/large satellites in the past due to the miniaturization and precision of electronic equipment, small satellite launches are expected to dominate in the future. In this paper, institutional certification methods such as domestic, overseas, civilian and military airworthiness certification regulations/procedures are reviewed to ensure flight safety of aerial projectiles using large domestic civil aircraft, and applicable civil and military airworthiness certification technology standards are reviewed and analyzed. Additionally, we will review and suggest effective airworthiness certification application plans that reflect the reality, and present airworthiness certification standards (draft) for aerial launch vehicles, by analyzing applicable airworthiness certification technical standards when remodeling aerial launch vehicles.