• 천문학논총
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• 제14권1호
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• pp.47-56
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• 1999

We have improved the control and driving system of 16' reflector at Kwanak Observatory at Seoul National University, by completing encoder unit, and by developing programs for correction of errors resulting from hardware defects. The hardware defects of this telescope system are the large backlash and the nonuniform tracking and pointing. The telescope pointing accuracy for RA is improved to a few arc minutes, and that for DEC is several tens of arc minutes. The guiding error is improved to 0.7 arcsec/minute, allowing up to 3 minutes exposure for CCD imaging under typical seeing conditions at the Observatory.

• 천문학논총
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• 제20권1호
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• pp.73-83
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• 2005

On-The-Fly (OTF) observation method is developed for the efficient use of 6 M radio telescope at Seoul Radio Astronomy Observatory (SRAO). This technique, in which data and information of antenna position are recorded synchronously while driving a telescope regularly and rapidly across a field, provides more efficient use of telescope time and better calibration of the acquired data than the traditional point-to-point observation method does. For the realization of the method, we (1) added RT-Linux modules to the existing operating system, (2) replaced digital voltmeter with voltage-to-frequency converter, and (3) modified many SRAO observation programs. By observing Moon and G78.2+2.7 using this method and comparing them with previous observations, we verify the successful operation and efficiency of the OTF observation mode.

• Journal of Astronomy and Space Sciences
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• 제17권1호
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• pp.45-52
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• 2000

충북대하교 교내천문대에 설치된 LX200 망원경으 구동장치가 가지고 있는 주기오차량을 측정하고, 이를 분석하여 보정하였다. 주기오차의 보정전에 측정한 오차의 표준편차는 $\sigma$=7."2 이었고, 주기오차를 보정한 후의 $\sigma$=1."2로 추적을 하는데 있어 정확도면에서 6배 향상되었다.

• 기술혁신학회지
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• 제14권1호
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• pp.40-59
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• 2011

우리나라 정부는 천문학 분야의 연구수준 향상을 위하여 대형광학망원경 개발사업을 추진 중이다. 그러나 대형광학망원경사업에는 막대한 예산이 소요되므로, 대형광망원경사업의 경제적 효과를 정량적으로 분석한 후 사업의 경제적 타당성 여부를 평가해야 한다. 이에 본 연구는 CVM을 활용하여 엄밀한 경제이론에 근거하여 대형광학망원경사업의 편익을 정량적으로 규명하고자 하였다. 분석 결과 대형광학망원경사업을 위한 연간 가구당 평균 지불의사액의 하한값이 1,416원으로 나타났다. 이를 전국의 전체 가구로 환산한 대형광학망원경사업의 경제적 편익은 연간 240.8억원에 이르는 것으로 나타났다. 이러한 분석결과는 대형광학망원경사업과 같은 대규모 과학기술 관련 투자사업의 타당성 평가를 위한 경제적 기초자료로 활용될 수 있다.

• 천문학회지
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• 제36권1호
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• pp.43-48
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• 2003

We introduce and describe performance of the 6-meter telescope of Seoul Radio Astronomy Observatory (SRAO). All the softwares and instruments except the antenna structure and its driving system are developed for ourselves. The SIS mixer type receiver resulted in the receiver noise temperature less than 50 K (DSB) over the whole 3-mm radio window. An autocorrelation spectrometer, developed first in Korea, provides maximum 50 MHz band width over 1024 channels. Antenna surface is measured and adjusted using template method and radio holography which resulted in a superb surface accuracy bet-ter than 30${\mu}m$. Accordingly, the aperture and beam efficiences amount to $70\%$ and $75\%$, respectively, largely independent of frequency in the 85 - 115 GHz range. It is also found that telescope pointing errors are less than 10" in both azimuth and elevation and that antenna gain is almost constant against elevation greater than $20^{\circ}$, without adjusting sub-reflector position. The SRAO 6-meter telescope is now fully operational and all these characteristics verify that observations are carried out with high precision and fidelity.

• 천문학회보
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• 제43권2호
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• pp.47.2-47.2
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• 2018

The umbral oscillations of velocity are commonly observed in the chromosphere of a sunspot. Their sources are considered to be either the external p-mode driving or the internal excitation by magnetoconvection. Even though the possibility of the p-mode driving has been often considered, the internal excitation has been rarely investigated. We report the observational evidence for the internal excitation obtained by analyzing velocity oscillations in the temperature minimum region of a sunspot umbra. The velocity oscillations in the temperature minimum region were determined from Fe I $5435{\AA}$ line data taken by the Fast Imaging Solar Spectrograph (FISS) of the 1.6 m Goode solar Telescope (GST) at the Big Bear Solar Observatory. As a result, we discovered 4 events of oscillations which appear to be internally excited. We analyze their characteristics and relation to photospheric features. Based on these results, we estimate the contribution of the internal excitation for umbral oscillations and discuss their importance.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 1993년도 한국우주과학회보 제2권2호
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• pp.21-21
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• 1993

The imaging areas of currently available optical detectors are relatively small to cope with large image areas such as telescope focal Planes. One Possibility to obtain large detection areas is to assemble mosaics of Charge Coupled Devices(CCDs) and drive them simultaneously. Parallel driving of many CCDs together rules out the possibility of individual tuning; however such optimisation is very important when the ultimate low light level performance is required particularly for new devices. In this work, a new concept has been developed for an entirely novel approach where the drive waveforms are multiplexed and interleaved. This simultaneously reduces the number of leadout connections and permits individual optimisation efficiently. The controller has been designed to include one electronic of component produced by CAD software where most of the digital circuits are integrated to minimise the component count and improve the efficiency of the system greatly. The software has an open architecture to permit convenient modificationl by the user to fit their specific purposes. The desire of controller allows great flexibility of system parameters by the softwa re, specifically for the compatibility to deal with any number of mixed CCDs and in any format within the practical limit. The system has been integrated to test the performance and the result is discussed for readout noise, system linearity and cross-talk between the CCDs. The system developed in this work can be applicable not only for astro nomical observation with a telescope but also in other related fields for low light level detection systems such as spectroscopic application, remote sensing and X-ray detecti13n systems with large sensing areas and high resolution.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 Techno-Fair 및 추계학술대회 논문집 전기물성,응용부문
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• pp.148-149
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• 2007

We present the design and fabrication prcoess of a two-axis tilting micromirror device driven by the electrostatic vertical comb actuator. A high aspect-ratio comb actuator is fabricated by multiple DRIE process in order to achieve large scan angle. The proposed fabrication process enables a mirror to be fabricated on the wafer-scale. By bonding a double-side polished (DSP) wafer and a silicon-on-insulator (SOI) wafer together, all actuators on the wafer are completely hidden under the reflectors. Nickel lines are embedded on a Pyrex wafer for the electrical access to numerous electrodes of mirrors. An anodic bonding step is implemented to contact electrical lines with ail electrodes on the wafer at a time. The mechanical angle of a fabricated mirror has been measured to be 1.9 degree and 1.6 degree, respectively, in the two orthogonal axes under driving voltages of 100 V. Also, a $8{\times}8$ array of micromirrors with high fill-factor of 70 % is fabricated by the same fabrication process.

• 천문학회보
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• 제45권1호
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• pp.44.1-44.1
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• 2020

Hα jets of cool chromospheric plasma are protruding into the solar corona 10-100 Mm above the photosphere. The driving mechanisms of Hα jets have been widely studied for decades. However, the detailed process is still elusive. We observed shock signatures moving along a dark jet using 1.6 meter Goode Solar Telescope at Big Bear Solar Observatory. The first shock front of the jet shows sharp --- when it moves upward, while fuzzy and granulated when it moves downward. The jet itself extends upward when the second shock front of the jet reaches the top of the jet. We find abrupt EUV brightenings when the second shock front collides with the edge of the jet. The third front and the fouth front quasi-periodically. These phenomena might be the signs of the rebound shock waves triggered by p-mode wave leakages at the bottom of the jets. Our observation suggests that the jet can be triggered by the rebound shock waves generated by the p-mode waves leaked at the bottom of the jets.

• 천문학회지
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• 제47권6호
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• pp.311-317
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• 2014

Solar chromospheric surges are often reported to contain rotational motion. However, the details of the motion and driving mechanism of the surges are not yet fully understood. Recurrent surges with rotational motion at AR 10930 on the west limb are observed by Hinode Solar Optical Telescope (SOT) continuously from 11:21 UT on December 18 to 09:58 UT on December 19, 2006, using the $Ca_{II}$ H broadband filter. We analyze details of the motion including number of turns from the rise of the surge to the fall, axial speed and acceleration. During the observation, rise and fall motion accompanying rotation appears recurrently. There occur a total of 14 surges at AR 10930 over 17 hours. The average duration is 45 minutes, and the average width, and length are 8 Mm, and 39 Mm, respectively. We speculate that the surges occurred by recurrent reconnections between the twisted prominence and large untwisted flux tube.