• 한국콘텐츠학회논문지
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• 제11권3호
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• pp.460-466
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• 2011

감은사는 첨성대가 건축되고 46년 후 서력 682년에 세워진 신라시대 사찰로 현재는 금당터와 석탑 및 각종 석조 유물로 전해지고 있다. 본 논문에서는 1959년 1차 발굴 때 감은사지 금당터의 동편에서 발견된 동편 태극 장대석과 2차 발굴 때 감은사지 남편 연못에서 발견되어 1993년 인위적으로 서편에 배치된 서편 태극 장대석에 대한 과학적 의미를 파악하기 위하여 유물에 각인된 도형의 기하학적 분석을 한다. 그리하여 감은사지 태극 장대석이 의미하는 수학적, 천문학적인 도형의 현대적 해석을 통하여 당시의 과학 수준을 가늠할 중요한 척도를 얻게 되었다. 또한 동편 및 서편 태극 장대석이 나타내는 이등변삼각형들의 배치가 각각 해와 달과 관련된 책력과 연관함을 추론하게 된다. 이러한 엄밀한 수학적 개념 조사를 통하여 역사적 사실이 빈약한 오래된 역사적 구조물을 이해하고 고증하는데 새로운 연구 방향을 제시해준다.

• 천문학회보
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• 제36권2호
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• pp.117.1-117.1
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• 2011

We present the smoothness of mid-infrared sky brightness from the Japanese infrared astronomical satellite, AKARI observations. AKARI monitored the north ecliptic pole (NEP) during its cold phase with nine wavebands from 2.4 to 24 ${\mu}m$, out of which six mid-infrared bands are used in this study. Simple sinusoidal fit to the seasonal variation of the sky brightness shows that the mid-infrared brightness towards the NEP is not affected by small-scale features of the interplanetary dust cloud. We applied the power spectrum analysis to the images to search for the fluctuation of sky brightness. The fluctuation powers at 200 arcsecond are estimated to be at most $1.58{\pm}0.33\;nW\;m^{-2}sr^{-1}$ or 0.13% of the total brightness at $7{\mu}m$ and a tleast $0.64{\pm}0.11\;nW\;m^{-2}sr^{-1}$ or 0.02% at $18{\mu}m$. The residual fluctuations at a few arcminute scales at short mid-infrared wavelengths (7, 9, and 11 ${\mu}m$) are consistent with those expected from the diffuse galactic light. At long mid-infrared wavelengths (15, 18, and 24 ${\mu}m$) the measured fluctuations are comparable to or smaller than the one caused by photon noise and their sources are not identified. We conclude that the upper limit of the fluctuation in the zodiacal light is about 0.02% of the sky brightness.

• 천문학회보
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• 제27권1호
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• pp.36-36
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• 2002

별똥에는 가랑 별똥(sporadic meteors)과 별똥비 (meteor shower)에 속하는 별똥이 있다. 우리는 고려사 천문지에 적혀 있는 별똥 기록을 조사하여 10세기에서 15세기까지 지구 공전 궤도 상의 별똥 알갱이의 분포에 대해서 연구하였다. 우리는 일년중 특정한 날짜에 별똥이 많이 떨어지는 시기가 몇 개 있음을 발견하였다. 우리는 이러한 별똥들이 별똥비에 해당할 것으로 가정하고 한국, 일본, 중국의 천문 기록 가운데 별똥 소나기 기록을 끄집어 내어 고려사의 별똥 기록에서 구한 별똥비 기록과 비교하였다. 그 결과 7월 27일 경에 강한 별똥비가 있었고, 몇 년 주기로 별똥 소나기가 떨어졌음을 알아 냈다. 우리는 고려 시대의 별똥 기록을 두개로 나누어 별똥비의 세기가 어떤 진화를 하는지는 연구하였다. 7월 27일에 나타난 별똥비는 그 세기가 줄어든 것을 알 수 있었다.

• 천문학회보
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• 제41권1호
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• pp.75.4-76
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• 2016

DEEP-South (Deep Ecliptic patrol of the Southern sky) is one of the secondary science projects of KMTNet (Korea Microlensing Telescope Network). The objective of this project is twofold, the physical characterization and the discovery of small Solar System bodies, focused on NEOs (Near Earth objects). In order to achieve the goals, we are implementing a software package to detect and report moving objects in the $18k{\times}18k$ mosaic CCD images of KMTNet. In this paper, we present preliminary results of the moving object detection experiments using the prototype MODP (Moving Object Detection Program). We utilize multiple images that are being taken at three KMTNet sites, towards the same target fields (TFs) obtained at different epochs. This prototype package employs existing softwares such as SExtractor (Source-Extracto) and SCAMP (Software for Calibrating Astrometry and Photometry); SExtractor generates catalogs, while SCAMP conducts precision astrometric calibration, then MODP determines if a point source is moving. We evaluated the astrometric accuracy and efficiency of the current version of MODP. The plan for upgrading MODP will also be mentioned.

• 천문학회보
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• 제41권1호
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• pp.56.2-56.2
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• 2016

We present a multi-aperture photometry pipeline for DEEP-South (Deep Ecliptic Patrol of the Southern Sky) time-series data, written in C. The pipeline is designed to do robust high-precision photometry and calibration of non-crowded fields with a varying point-spread function, allowing for the wholesale search and characterization of both temporal and spatial variabilities. Our time-series photometry method consists of three parts: (i) extracting all point sources with several pixel/blind parameters, (ii) determining the optimized aperture for each source where we consider whether the measured flux within the aperture is contaminated by unwanted artifacts, and (iii) correcting position-dependent variations in the PSF shape across the mosaic CCD. In order to provide faster access to the resultant catalogs, we also utilize an efficient indexing technique using compressed bitmap indices (FastBit). Lastly, we focus on the development and application of catalog-based searches that aid the identification of high-probable single events from the indexed database. This catalog-based approach is still useful to identify new point-sources or moving objects in non-crowded fields. The performance of the pipeline is being tested on various sets of time-series data available in several archives: DEEP-South asteroid survey and HAT-South/MMT exoplanet survey data sets.

• 천문학회보
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• 제41권1호
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• pp.55.1-55.1
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• 2016

Near Earth Asteroid (NEA) population has attracted keen attention not only from the scientific community but from the general public ever since their terrestrial impact risk achieved wide recognition. Potentially Hazardous Asteroids (PHAs), the subset of NEAs, recently became the center of interest of planetary defense folks and mining industry due to their proximity to, and the potential effects on planet Earth. However, we have long been ignorant about either the physical properties or dynamical source regions of individual objects. For instance, their rotational periods are only known for five percent of the total population (The NEA Database of DLR, updated on Feb 2016). The primary scientific objective of DEEP-South (DEep Ecliptic Patrol of the Southern sky) is to physically characterize 70 percent of km-class PHAs until 2019. In order to achieve this goal, we implemented an observation mode so-called "OC (Opposition Census)" targeting objects around opposition. OC observations were conducted during the period between Feb 2015 and Mar 2016, at CTIO in early periods, and at three KMTNet stations (CTIO, SSO and SAAO) since late July 2015, excluding the "bulge season" when the telescope time is exclusively used for exoplanet search. We present the preliminary lightcurves of 66 PHAs and 59 NEAs that we obtained during the OC runs.

• 천문학회보
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• 제41권1호
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• pp.54.2-54.2
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• 2016

Korea Microlensing Telescope Network (KMTNet) is the first optical survey system of its kind in a way that three KMTNet observatories are longitudinally well-separated, and thus have the benefit of 24-hour continuous monitoring of the southern sky. The wide-field and round-the-clock operation capabilities of this network facility are ideal for survey and the physical characterization of small Solar System bodies. We obtain their orbits, absolute magnitudes (H), three dimensional shape models, spin periods and spin states, activity levels based on the time-series broadband photometry. Their approximate surface mineralogy is also identified using colors and band slopes. The automated observation scheduler, the data pipeline, the dedicated computing facility, related research activity and the team members are collectively called 'DEEP-South' (DEep Ecliptic Patrol of Southern sky). DEEP-South observation is being made during the off-season for exoplanet search, yet part of the telescope time is shared in the period between when the Galactic bulge rises early in the morning and sets early in the evening. We present here the observation mode, strategy, software, test runs, early results, and the future plan of DEEP-South.

• 천문학회보
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• 제39권1호
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• pp.54.1-54.1
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• 2014

Kyung Hee University has been developing a CubeSat for the space science mission called SIGMA (Scientific cubesat with Instrument for Global Magnetic field and rAdiation), which includes TEPC (Tissue Equivalent Proportional Counter) and a magnetometer. SIGMA has a 3-unit CubeSat, and the weight is about 3.2 kg. The main payload is TEPC which can measure the Linear Energy Transfer (LET) spectrum and calculate the equivalent dose for the complicated radiation field in the space. The magnetometer is a secondary payload using a miniaturized fluxgate magnetometer. We expect it to have a 1 nT resolution in the dynamic range of ${\pm}65535$ nT. An Attitude Control System (ACS) spins the SIGMA spacecraft 4 rpm with the spin axis perpendicular to the ecliptic plane. Full duplex communication is consists of VHF uplink and S-band and UHF downlink. In this paper, we introduce the system design and the scientific purpose of the SIGMA CubeSat mission.

• 항공우주기술
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• 제10권2호
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• pp.29-36
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• 2011

과학기술위성 3호는 우리별 위성 시리즈와 과학기술위성 1호, 2호를 잇는 소형위성으로 첨단 위성체 핵심 기술 선행연구, 첨단 우주 및 지구 과학 탑재체 개발, 우주분야 인력 양성 등의 다양한 역할을 수행한다. 과학기술위성의 주탑재체는 다목적 적외선 영상시스템으로 우리은하와 황도극지방을 관측하여 우주의 기원을 연구한다. 다목적 적외선 영상시스템에는 국산 적외선 센서의 우주검증을 위해 지표면의 적외선 영상 획득 임무도 추가되었다. 부탑재체는 초소형 영상 분광기로서 농작물의 작황, 댐의 수질 예측 모델, 에어로졸 광학 두께 측정 연구 등에 활용된다. 본 논문에서는 2012년 말에 발사되어 주어진 임무기간 동안 과학기술위성 3호의 다양한 임무 수행을 위한 운영개념을 설명한다.

• 천문학회지
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• 제51권5호
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• pp.129-142
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• 2018

The DEEP-South (the Deep Ecliptic Patrol of the Southern Sky) photometric census of small Solar System bodies produces massive time-series data of variable, transient or moving objects as a by-product. To fully investigate unexplored variable phenomena, we present an application of multi-aperture photometry and FastBit indexing techniques for faster access to a portion of the DEEP-South year-one data. Our new pipeline is designed to perform automated point source detection, robust high-precision photometry and calibration of non-crowded fields which have overlap with previously surveyed areas. In this paper, we show some examples of catalog-based variability searches to find new variable stars and to recover targeted asteroids. We discover 21 new periodic variables with period ranging between 0.1 and 31 days, including four eclipsing binary systems (detached, over-contact, and ellipsoidal variables), one white dwarf/M dwarf pair candidate, and rotating variable stars. We also recover astrometry (< ${\pm}1-2$ arcsec level accuracy) and photometry of two targeted near-earth asteroids, 2006 DZ169 and 1996 SK, along with the small- (~0.12 mag) and relatively large-amplitude (~0.5 mag) variations of their dominant rotational signals in R-band.