https://repository.kopri.re.kr/handle/201206/11545 2026-04-19T01:04:23Z https://repository.kopri.re.kr/handle/201206/13587 Title: VHF/UHF Open-Sleeve Dipole Antenna Array for Airborne Ice Sounding and Imaging Radar Authors: Won, Hoyun; Hong, Yang-Ki; Li, Linfeng; Awasthi, Abhishek; Nickerson, Natalie; Bryant, Briana; Choi, Minyeong; Yan, Stephen; Taylor, Drew; O'Neill, Charles; Lee, Joohan Abstract: This letter presents a simple, lightweight, and ultrawideband, the very high frequency/ultrahigh frequency (VHF/UHF) open-sleeve dipole antenna array for airborne ice measuring radar. The proposed antenna array achieves a wide bandwidth of 300 MHz via mutual coupling from neighboring excited elements. A hollow aluminum tube is used for both dipole and parasitic elements to minimize the antenna's weight. The simulation results show that to achieve a bandwidth of 300 MHz with a peak realized gain up to 12 dBi in the frequency range from 170 to 470 MHz, the length of the dipole (L-dip) and parasitic elements (L-para) of elements 1 and 4 of the four-element antenna array need to be 670 mm and 200 mm, respectively. At the same time, elements 2 and 3 require an L-dip of 640 mm and L-para of 180 mm. Based on these dimensions, a four-element antenna array is fabricated and tested. The measured antenna performance results show a good agreement with the simulated results. 2021-06-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/11869 Title: Time-Lapse Electrical Resistivity Structures for the Active Layer of Permafrost Terrain at the King Sejong Station: Correlation Interpretation with Vegetation and Meteorological Data Authors: Kim, KwanSoo; Lee, Joohan; Lee, Eungsang; Ju, Hyeon Tae; Hyun, Chang-Uk; Park, Sang-Jong; Kim, Ok-Sun; Lee, Sun-Joong; Kim, Ji-Soo Abstract: Over the wide area, King Sejong Station and the nearby land are uncovered with snow and ice conditions. Therefore, the active layer on the permafrost has been formed to be much thicker than the other Antarctica region. Electrical resistivity survey of Wenner and dipole-dipole arrays was undertaken at a series of time in the freezing season at the King Sejong Station to delineate subsurface structure and to monitor active layer in permafrost terrain. Time-lapse resistivity structures are well in terms of the vegetation distribution, ground surface temperature, and snow depth. Horizontal high resistivity belt(>1826 Ωm) at very shallow depth is thickening with the lapse of time, probably caused by the freezing of the water in the pore spaces with decrease of ground temperature. Subsurface structures for the area of low snow-cover and vegetated zone area are comprised of 0~0.5 m deep high-resistive gravel-rich soil, 0.5~3 m deep low-resistive active layer, and the underlying permafrost. In contrast, the unvegetated area and high snow-buildup is characterized with high resistivities larger than approximately 2000 Ωm due to freezing of the soil throughout the year. Data interpretation and correlation schemes explored in this paper can be applied to confirm the active layer, which is expected to get thinner in additional survey during the thawing season. 2020-08-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/13061 Title: Aerogeophysical characterization of an active subglacial lake system in the David Glacier catchment, Antarctica Authors: Lindzey, Laura E.; Beem, Lucas H.; Young, Duncan A.; Quartini, Enrica; Blankenship, Donald D.; Lee, Choon-Ki; Lee, Won Sang; Lee, Jong Ik; Lee, Joohan Abstract: In the 2016-2017 austral summer, the University of Texas Institute for Geophysics (UTIG) and the Korea Polar Research Institute (KOPRI) collaborated to perform a helicopter-based radar and laser altimeter survey of lower David Glacier with the goals of characterizing the subglacial water distribution that supports a system of active subglacial lakes and informing the site selection for a potential subglacial access drilling project. This survey overlaps with and expands upon an earlier survey of the Drygalski Ice Tongue and the David Glacier grounding zone from 2011 and 2012 to create a 5 km resolution survey extending 200 km upstream from the grounding zone. The surveyed region covers two active subglacial lakes and includes reflights of ICESat ground tracks that extend the surface elevation record in the region. This is one of the most extensive aerogeophysical surveys of an active lake system and provides higher-resolution boundary conditions and basal characterizations that will enable process studies of these features. This paper introduces a new helicopter-mounted ice-penetrating radar and laser altimetry system, notes a discrepancy between the original surface-elevation-derived lake outlines and locations of possible water collection based on basal geometry and hydraulic potential, and presents radar-based observations of basal conditions that are inconsistent with large collections of ponded water despite laser altimetry showing that the hypothesized active lakes are at a highstand. 2020-07-15T00:00:00Z https://repository.kopri.re.kr/handle/201206/12255 Title: Effective Glacier Seismic Survey Method Applied on Glacier - Case : Configuration of the Subglacial Lake under the David Glacier, Antarctica Authors: Ju, Hyeon Tae; Kang, Seung-Goo; Kim, KwanSoo; Kim, Ye-Dong; Lee, Joohan Abstract: 남극 빙상은 다 녹는다면 전세계 해수면을 58m나 상승시킬 수 있는 막대한 크기이다. 현재 해수면 상승에 큰 영향을 미치고 있는 남극 빙상의 변화는 지구온난화 뿐만 아니라 빙상 하부의 지형이나 수리학적 특성 등에 따른 빙하의 흐름에도 영향을 받는다. 특히, 빙저호의 형성과 관련된 빙저수의 존재는 지면과의 마찰력을 감소 시켜 빙상의 흐름을 제어하는데 큰 역할을 한다. 본 연구를 통해 2016년부터 남극 장보고과학기지에서 남쪽으로 약 250km 떨어진 데이비드 빙하에서 D2 빙저호 후보지를 지속적으로 관찰하였다. 위성자료에 따르면 D2 지역은 2011-18년 사이 17m의 빙상 고도 상승이 관측되어 빙저호의 유력한 후보지로 파악되었다. 2017년과 2018년 D2 빙저호 후보지 전지역에 걸쳐 1km 간격의 격자 측선을 따라 실시된 항공 빙하레이더(Ice radar) 조사를 통해 수치표고모델(Digital elevation model)이 작성되었다. 빙하의 평균 두께는 약 1.6 ？ 2.3 km 이며, 빙하레이더 자료를 기초로 추후 빙저호 시추 후보지역의 정밀 수치표고모델을 완성하고자 2019년 12월 D2 지역 빙하에서 반사법 탄성파 1차 탐사를 실시하였다. 빙하 위에서 수행되는 탄성파 탐사에서는 기존 육상 탐사와 달리 표면에 다져진 눈층(firn)이 탄성파 에너지를 급격히 감쇠시키는 문제가 발생한다. 이를 극복하기 위해 발파공 심부굴착을 위한 열수시추기와 설상 지오폰(지오로드) 등 국내 소개된 적 없는 장비를 이용하였다. 데이비드 빙하 지역(S75.42°/E155.47°) 빙하 표면은 약 20 m 두께의 다져진 눈층으로 덮혀 있어, 탄성파 에너지원 효율을 향상시키기 위해 열수시추를 사용하여 약 20-30 m 깊이의 시추공에 800-1200 그램의 탐사용 화약을 설치하였고, 기존 1채널 지오폰 대신 4채널 중합 지오폰인 지오로드를 사용하여 수신 신호 효율을 향상시켰다. 탐사에서는 4km와 7km의 두 개의 측선에 단일 중첩(single-fold)으로 12번(4km)과 19번(7km)의 발파가 이루어졌으며, 발파 간격 360m, 채널 간격 15m, 48채널 기록계로 자료를 획득하였다. 획득된 자료로부터 얼음-호수 경계면에서의 강한 반사파와 위상역전 현상을 관찰할 수 있었다. 2020-01-01T00:00:00Z