• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.1
• /
• pp.35.2-35.2
• /
• 2011

We have investigated a coronal jet near the limb on 2010 June 27 by Hinode/X-Ray Telescope (XRT), EUV Imaging Spectrograph (EIS), SDO/Atmospheric Imaging Assembly (AIA), and STEREO. From EUV (AIA and EIS) and soft X-ray (XRT) images we identify the erupting jet feature in cool and hot temperatures. Using the high temporal and multi wavelength AIA images, we found that the hot jet preceded its associated cool jet and their structures are well consistent with the numerical simulation of the emerging flux-reconnection model. From the spectroscopic analysis, we found that the jet structure changes from blue shift to red one with time, which may indicate the helical structure of the jet. The STEREO observation, which enables us to observe this jet on the disk, shows that there was a dim loop associated with the jet. On the other hand, we found that the structure of its associated active region seen in STEREO is similar to that in AIA observed 5 days before. Based on this fact, we compared the jet morphology on the limb with the magnectic fields extrapolated from a HMI vector magnetogram of this active region observed on the disk. Interestingly, the comparison shows that the open and closed magnetic field configuration correspond to the jet and the dim loop, respectively, as the Shibata's jet model predicted.

• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.1
• /
• pp.28.1-28.1
• /
• 2011

We observed the transiting exoplanet, TrES-2b, with 1.5m telescope at Maidanak Observatory in Uzbekistan. We observed TrES-2 system for six nights, which contained two orbital periods of the planet. Therefore, we obtained the entire light curve of TrES-2b, which covered not only the whole primary transit containing both ingress and egress part, but also non-transit region. We used both R and Y band filters. Especially, Y filter is used first for transit observation and covers relatively longer wavelength ($1.02{\mu}m$ of center wavelength), to provide the light curve less affected by limb darkening. By fitting best model light curve for the obtained one, we determined these observables, transit depth, transit length, and planet's orbital period, which led to the determination of five physical parameters, stellar radius R*, stellar mass M*, inclination i, semi-major axis a, and planetary radius Rp. We will discuss of these results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.22 no.12
• /
• pp.164-175
• /
• 2008

Atmospheric effects on laser beam propagation can be broken down into two categories: attenuation of the laser power and fluctuation of laser power due to laser beam deformation. Attenuation consists of scattering of the laser light photons by the fog. Laser beam deformation occurs because of small-scale dynamic changes in the index of refraction of the atmosphere. This causes pointing error. In order to analyse these effect on optical wireless communication system, in this paper uses cassegrain optics as a transmitting and receiving telescope, AID as a detecting device and ill as a light source. The signal modulating and demodulating method is a IM/DD. I show the effects of fog and pointing error and calculate the possible communication distance for BER is $10^{-9}$.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2009.04a
• /
• pp.226-229
• /
• 2009

최근 들어 인터넷 게시판이나 개인 블로그 등은 온라인상에서 사람들의 정보 공유나 의견 교환의 중요한 매체가 되고 있다. 많은 수의 블로그들은 현재 사회적으로 이슈가 되는 여러 문제들을 반영하고 있다. 또한 최근 댓글을 통해 적극적으로 자신의 의사 표현하거나 다른 사람들의 의견을 살피는 인터넷 사용자의 증가로 인터넷 뉴스나 블로그 기사에 많은 수의 댓글이 달리고 있다. 그러나 대부분의 블로그나 인터넷 포털 사이트의 경우 기사나 댓글들을 순차적인 목록 형태로 제공하므로 자신이 원하는 내용의 댓글을 검색하거나 전체 댓글에 대한 전반적인 파악은 힘든 일이다. 따라서 본 논문에서는 기사에 달린 많은 수의 댓글들을 분류하고, 이를 시각화 하는 시스템인 TRIB(Telescope for Responding comments for Internet Blog)을 제안한다. TRIB은 미리 정의된 사용자 정의 사전을 이용하여 댓글을 내용에 따라 분류하여 시각화 하므로 사용자들은 자신의 관심과 흥미에 따라 개인화 된 뷰를 볼 수 있다. 1,000개 이상의 댓글을 가진 뉴스 기사들을 대상으로 한 실험을 통해 TRIB 시스템의 댓글 분류와 시각화 성능을 보인다.

• Journal of Astronomy and Space Sciences
• /
• v.28 no.4
• /
• pp.333-344
• /
• 2011

An optical tracking system has advantages for observing geostationary earth orbit (GEO) satellites relatively over other types of observation system. Regular surveying for unidentified space objects with the optical tracking system can be an early warning tool for the safety of five Korean active GEO satellites. Two strategies of positioning on the observed image of Communication, Ocean and Meteorological Satellite 1 are tested and compared. Photometric method has a half root mean square error against streak method. Also eccentricity method for initial orbit determination (IOD) is tested with simulation data and real observation data. Under 10 minutes observation time interval, eccentricity method shows relatively better IOD results than the other time interval. For follow-up observation of unidentified space objects, at least two consecutive observations are needed in 5 minutes to determine orbit for geosynchronous orbit space objects.

• Journal of Satellite, Information and Communications
• /
• v.8 no.3
• /
• pp.32-40
• /
• 2013

The Boltwood Cloud Sensor is meteorological sensor that is used to estimate an amount of clouds in the sky. This sensor will be installed for OWL(Optical Wide-field patroL) telescope and observatory system of Korea Astronomy and Space Science. Before applying this sensor to an observatory system, we performed test observations at Chungbuk University Observatory at Jincheon, Chungbuk. During the test run, a significant correlation between air temperature difference and the number of visible stars recorded in the CCD frames has not been found. This preliminary result can be attributed to test environment of the observation and our lack of knowledge on calculation algorithm as well as the hardware system of the Boltwood Cloud Sensor.In this paper, we present the procedure and the result of the performance test employing the cloud sensor.

• Journal of Astronomy and Space Sciences
• /
• v.25 no.1
• /
• pp.61-70
• /
• 2008

As the second step of the real time monitoring system of the solar radio disturbance, we constructed a 2.8 GHz radio receiver with 500 MHz bandwith. Using the control and observing system (Yoon et al. 2004), we observed the Sun, and found some frequencies, which disturb the Solar radio flux to be observed. DMB and aiport control frequencies are identified as responsible for this disturbance. As well as the testing the receiver, the measurment of the radio environment at 2.8 GHz with 500 MHz bandwith are carried out around Chungbuk National University. In fact, the radio power of the two frequencies, 2.649 GHz and 2.874 GHz is so high that we can not observe the Solar radio signal at 2.8 GHz. We report some results of this measurment and suggest the method to overcome this problem. We conclude also that the frequecies, which are important for the astronomy, should be protected in the future.

• Journal of The Korean Astronomical Society
• /
• v.46 no.6
• /
• pp.225-234
• /
• 2013

We develop a radio receiver system operating at ${\lambda}{\sim}1.3$ mm for the 6 m telescope of Seoul Radio Astronomy Observatory. It consists of a dual polarization receiver, a couple of IF processing units, two FFT spectrometers, and associated software. By adopting sideband-separating superconductor mixers with image band terminated to waveguide load at 4.2 K, we achieve $T_{RX}{\leq}100$ K and $T_{sys}$ less than 150 K at best weather condition over 210-250 GHz frequency range. The intermediate frequency signal of 3.5-4.5 GHz is down converted to 0-1 GHz and fed into the FFT spectrometers. The spectrometer covers 1 GHz bandwidth with a spectral resolution of 61 KHz. Test observations are conducted toward several radio sources to evaluate the performance of the system. Aperture and beam efficiencies measured by observing planets are found to be typically 44 ~ 59% and 47 ~ 61%, respectively over the RF band, which are consistent with those measured at 3 mm band previously.

• Korean Journal of Optics and Photonics
• /
• v.16 no.6
• /
• pp.521-526
• /
• 2005

We assembled the optical beam director with diameter 300 mm. This consists of primary, secondary mirrors and 5 folding mirrors. Among them, the primary mirror is the most important component so that we measure any possible deformation on it at every step of assembly. Also, we developed the systematic alignment algorithm, which is essential because the number of mirrors is 7. The final wavefront error of the system is 1.9 wave rms (wave=633 nm) which is 7 times larger than we expected. The main source is the deformation of the 131ding mirrors. We expect that what we have learned from the assembly of this system would be helpful when we deal with a larger system in the future.

• Journal of Astronomy and Space Sciences
• /
• v.26 no.1
• /
• pp.111-126
• /
• 2009

We used an optical observation system with a 0.6m wide-field telescope and 5 computers system in KASI (Korean Astronomy and Space Science Institute) for satellite optical observation. Optical data have errors that are caused by targeting, expose start time and end-point determination. Gauss method for initial orbit determination was tested using angle-only data simulated by KODAS. And suitable time span is confirmed for result which has minimum errors. Initial orbit determination results are proved that optical observation system in KASI is possible satellite tracking for a short period. And also through differential correction, initial orbit determination results are improved.